Tony's Blog

Budget Milestag Gun Kit

2012-02-03T13:43:00.000-08:00

I've been mad busy at work and not had time to continue with my build of my budget Milestag gun kit.This is meant to be a single gun body with an integral infra red sensor:

However I found a bit of time to continue the build this evening. Here is a view of the Sparkfun LED Display and 50MM speaker mounts:

This shows the other side of the gun body with the battery compartment and keyswitch:

New DIY UMT design

2012-01-19T15:36:00.000-08:00

I've modified my Milestag UMT design to correct a problem with the original.

The problem is that the muzzle flash LED is wired in parallel with the infra red LED:

This is an issue because the forward voltage of the IR emitter is 1.35V, and that of the muzzle flash LEDis 2.1V. This results in the muzzle flash illuminating far below its potential.

My new design has two outputs, one for the IR LED, and one for the muzzle flash LED. Both are driven from the same MOSFETbut the current limit resistor is dedicated to the IR LED:

The muzzle flash LED will require its own current limiting resistor, but this matches the original Milestag design.

Here's the PCB, it will be available as a kit at TAGBITS in a few weeks:

Bugdet Milestag- Continued

2012-01-18T15:46:00.000-08:00

I've been continuing the development of my budget Milestag gun kit. This is designed to have a singlesensor on the gun body to reduce the cost of the unit.Initially I've concentrated on the sensor electronics. I've created a kit to make a Milestag sensor:

Here it assembled. Surface mount components are a lot easier to solder than through hole:

This needs to be mounted in a sensor housing that can be fitted to the breech section of my Tagbits Guns,I've designed a special mount for this sensor type. I'll be building the gun in the next few days:

AMP-lified

2012-01-18T15:33:00.000-08:00

The Milestag CORE and UMT PCBs use 0.1" Vero connectors. These are a painto use in quantity as every cable has to crimped manually.I've started using AMP 0.1" IDC connectors instead. These are much faster to wire:

A friend of mine uses fine snipe nose pliers to force the wire onto the connectors. I found this unsatisfactory so I made myself an IDC crimp tool from aM8 bolt:

This pushes the cable into the IDC connector nicely:

Battery Cover

2012-01-16T14:27:00.000-08:00

Whilst getting ready to try out my single sensor Milestag gun I decided that Ineeded to re-design the battery cover on the gun body. Previously this had been quite thin and had chamfered, circular tabs that were proving difficultto print as the filament often failed to adhere to the layer below as the radius increased with the chamfer:

I redesigned the cover to have rectangular tabs. These should be easier to print with a chamfer:

I then subtracted this shape from the gun body, and increased all the edges by 0.2mm in size to allow for a good fit.

As the gun body is quite large, it takes a long time to print so I cut out from my model the part I was interested in and printed that:

I then printed the new battery cover:

The new cover slots nicely into the body cut outs and does not need any finishing to make it fit:

Sensor PCBs 2

2012-01-12T15:36:00.000-08:00

I've just taken delivery of my Milestag Compatible sensor PCBs:

I'll be making these available ready made and in kit for at Tagbits in the next few days.

TSOP4856

2012-01-12T15:30:00.000-08:00

I've just included Vishay TSOP4856 sensors at Tagbits

The Full Monty

2012-01-11T14:59:00.000-08:00

Here is a pic of my RepRap complete with heated chamber, acrylic door and filament spool holder. It's printing a grip section from one my Milestag guns.

At the bottom right you can see the hot air gun that I use to maintain the chamber temperature. I keep the machine in my garage and it struggles to get up to temperature with heat from the heated bed alone.

Second Sight

2012-01-02T14:21:00.000-08:00

I've been asked by several people whether it would be possible to mount a sensor on the gun bodies sold at Tagbits soI re-designed a sensor mount to fit onto the forestock section. When fitted with a 3 way milestag sensor this should allow for a low cost solution, but will allow body mounted sensors to be added later if required:

Here's a view looking down on the Milestag Gun

Here is the printed part fitted with an acrylic dome:

The underside has been modified to ensure the dome mounting screws and M3 nut are flush:

Here is the part on one of my Mk4 guns:

Looking at the height of the dome on the CAD model, I was concerned that the dome might obscure the optical red dot sight:

A rather poor camera shot down the sight confirms this. The bright dot is the 'red dot' of the sight:

I am going to have to re-engineer my picatinnny rail mount to be higher. A second sight.

2012 Spares

2012-01-02T09:37:00.000-08:00

After my extruder mount failed the other week, I declared that I needed to stock up on spare parts for my RepRap.I've printed this set of bits which is all but one of the components that I have identified as critical.

After printing the missing part I'll have a full set of spares. I really need to have pairs of some of these fittings though, namely the bar and linear bearing clamps as it doesn't really make sense to replace one of these in isolation.

Axis of Evil:Fixed

2011-12-24T15:08:00.000-08:00

Because it's Christmas Eve I was really sociable and retired to the workshop to create a new mounting bracket for my Wade extruder.Reprap is like a drug. You've got to print stuff, and when you can't you have to fix it. Anyhow, I found some 1.6mm steel sheet in my materials stash and made this:

To make it I printed a 1:1 2d plot of the piece, then glued this to the steel with 3M Spray Mount. I then use an optical centre punch to centre the holes, then opened them up with a 3mm spotting drill before drilling through with a 4MM HSS bit. The larger holes I drilled with a stepped drill bit.Here is it fitted to my RepRap bot:

Lesson: Identify critical parts on the RepRap and make sure you print spares!

(Z) Axis of Evil

2011-12-24T05:22:00.000-08:00

I successfully completed another 8 hour print yesterday, but I caught the Wade extruder mount with my hand and this happened:

I've been printing spares for my machine on and off for months. Unfortunately I hadn't got around to this part:

I'll just have to make a metal version of it by hand.

Printing on Kapton Tape

2011-12-23T02:51:00.000-08:00

Nophead lent me some Kapton tape and I tried an ABS print on it last night:

It is an 8 hour print of a large part, it came out really well:

Although the part was much more firmly attached to the kapton than I've seen with PET tape, it still managed to lift the tape slightly at the corners:

I'd really like to eliminate this lifting if I can. It has not spoiled the printed part because as a percentage of the overall part size it is negligible. I'm going to try again with a higher chamber temperature. The above was done with a chamber temp of 42-45C.The tape though is great. It is 150mm which is exactly the width of my heated bed, so applying it is easy when I used the technique described below.This helps to avoid the inevitable bubbles when dealing with large adhesive tapes:

Bunged Up

2011-12-18T13:54:00.000-08:00

Here's a video of my RepRap behaving as it should:

But for the last month or so I've been having problems. At random times the extruder started chewing filament instead of pushing into the heater. This of course resulted in failed prints. The first symptoms are particles of ABS accumulating on the idler bearing of the Wade extruder:

If allowed to continue printing, the extruder simply stops pushing ABS into the heater. On dismantling the extruder the hobbed bolt looks like this:

After cleaning with acetone it's pristine once again:

But after cleaning, sometimes I mange to get 2 or three large parts before another failure, othertimes it fails at the first print. I've tried reducing the flow rate of the extruder but this hasn't had any effect. The only consistent thing is that the print always fails on the second or third layer, never the first.

I got the nozzle from Wolfgang at RepRap Fab and I've bought a new one to see if this will improve things.

Buy Demand

2011-12-01T15:44:00.001-08:00

I've posted on several forums that I'm open to suggestions for parts and kits to be available at www.tagbits.co.uk . One suggestion was for a Milestag CORE gun kit to complement the existing
Milestag UMT kit.

As I already had a design for the CORE module, I've added a CORE kit to the shop here.

Tagbits.co.uk launched

2011-11-12T15:03:00.001-08:00

I've launched Tagbits.co.uk today. Basically I've made available all the Lasertag stuff I've been making over the last few months. Enjoy:

Tagbits

More Dome Bases

2011-11-03T15:56:00.000-07:00

I've spent the last week or so testing my designs for different sensor dome mounts. These will allow me to mount Milestag sensors with sewing, velcro, press studs or 32mm elastic belts. These also have angled cable exits making it easier to get the cables out. I've had trouble getting the radius of the centre of the mounting screws correct, having cracked several domes but I've managed to fix this now and can get the domes realiably fastened to the bases 100% of the time.

The selection below is now available at www.tagbits.co.uk

New Sight Rail 2

2011-10-20T00:32:00.000-07:00

Finally got my new sight rail printed for my Milestag gun. It is made up of several parts which are glued together. I need to improve the way the parts are aligned, but aesthetically it looks pretty good:

Here it is attached to a gun:

New Sight

2011-10-17T15:07:00.000-07:00

I've realised that some Milestag users prefer to mount an IR sensor on the gun itself (TonyC!). The problem with my existing design is that if the sensor is mounted forward of the sight, it is visible when looking through the sight.

To fix this, I've designed an M16 style sight raiser.This has been designed so that it can be fitted with either a picatinny rail or normal 'iron (ABS!) sights'. Looks pretty good on the CAD. Printing now...

In Focus

2011-10-05T14:42:00.000-07:00

I've finally run out of the plano-convex lenses I bought last year from Surplus Shed. These were great as they had a 50mm or so focal length which resulted in a short IR focus tube. I've ordered some more lenses but these have a FL of 100mm, therefore I needed to re-design the focus tube of my tag guns.

I changed the tube design to be in two parts. One holding the LED mount, endcaps and focus screw. A second tube is designed to slide over the first, but also it can be lengthened/shortened or given a larger diameter to suit the lens being used.

I forced the two parts together in my carpenters vice.

The ridges produced by the RepRap process interlock providing a fantastic strong joint. No glue is needed, I'm not going to get these two apart in a hurry.

Here is a complete IR tube kit. These are now available at Tagbits:

Full Kit

2011-09-28T14:48:00.000-07:00

Here is a photo of a complete kit of parts for a UMT based Milestag gun. Apart from the 20mm barrel, all parts have been printed with RepRap. I'm quite pleased with the results. I'm able to manufacture parts that, once printed, can be assembled into a functional device within an hour or so. long live RepRap!

This kit, and its Milestag Core brother are now availabale at tagbits.co.uk

These parts come together to make this:

UMT Mk4

2011-09-25T11:06:00.000-07:00

I've recently completed a Mk4 version of my RepRap'ed Milestag lasertag gun.This version has a a serially driven 4 x 7 segment LED display to indicate health/ammo which I got from RoboSavvy.This is driven from my homemade Milestag UMT PCBs. These have turned out really well. The only issue that I had was the corrupted display I mentioned previously.Here is a Mk4 complete with DIY acrylic dome sensors:

This has my new style muzzle flash suppressor attached. This differs from previous models in that it has side slots to allow light to show through:

All around my hat.....

2011-09-17T15:01:00.000-07:00

When I made my first Reprap'ed Milestag gun I designed a small PCB to allow the IR sensors to be connected to the gun housingwith a curly RJ10 lead. I initially fastened this PCB to the baseball cap by fastening them with tie-wraps. Hardly satisfactory.

I didn't advance on this rather crude method until now. I designed a small box to contain the PCB with mounting tabs to allow it to be fastened to the basball cap with press studs.It has two slots on the top and bottom halves for the PCB to slot into and some tabs for studs to be attached:

Here it is fitted to a cap. Much neater:

More domes

2011-09-12T14:42:00.000-07:00

I've almost completed my Mk4 RepRap Milestag gun and I needed to make some sensor domes with mountingsthat allow me to fasten the sensors to a baseball cap. I started out by maing six more domes from acrylic sheet as detailed here.To do this I modified the dome mount I made some time ago. I needed to modify the dimensions slightly as my domes have an internal diameter slightly larger than the onesI got from Lasertagparts.Here are the two parts:

Rather than potting the PCB and dome in place, my design uses three screws to hold it in place. This allows it to be dismantled for maintenance.

I SPI

2011-09-07T13:58:00.000-07:00

I've been doing further assembly on my Milestag UMT PCB. I bought a serially driven 7 segment display module from Sparkfun. This moduleis the one recommended for use with the Milestag UMT board. It is used to display clip rounds remaining and life.However, I could not get the display to function correctly. I sometimes (about 80% of the time) got a corrupted display.I resorted to removing the PIC MPU from the PCB and wiring it up on a breadboard with just the display and run from astabilised PSU. I still got the same results:

This should be displaying " 042".I made various attempts to fix it: Rewiring, shielded cable, more filtering caps, shorter sires. Nothing worked.I then noticed that when I picked the display up, it changed. I noted that this module has both SPI and TTL level serial inputs and when I touched the TTLinput the display became corrupted.TTL level serial idles at logic 1, so I tied the serial input line high and I haven't seen any corruption since. The module accepts segment levelcommands. i.e. You can send 4 bytes of data representing the segments in each digit. Obviously the serial input was getting noise and thiswas being interpreted as a valid display command.

ABSsolutely fabulous

2011-08-26T13:08:00.000-07:00

Now that I have my PLA extruder up and running, the acid test for me was the ability to switch between PLA and ABS easily. I swapped the extruders around in about 10 minutes. Most of this time was waiting for the heaters to get hot enough to allow me to remove/insert the filament.

With the ABS extruder in place, the first print I did came out perfectly without any need to re-calibrate. It's a picatinny rail sight mount for my Milestag lasertag gun.

Here it is sprayed up and with a sight mounted on my MK3, RepRap printed gun:

My wife is an avid photographer so I printed her one of kitlaan's lens cap holders.

It was printed with white ABS but I sprayed it black with the same paint I use for my guns. It came out very well.

The quick change extruder mount that I got from wolfgang has allowed me to change extruders without undoing a single bolt, and, more importantly, maintain calibration between changes.

PLA

2011-08-24T15:54:00.000-07:00

I've recently been trying to print PLA. A hard, transparent plastic that nophead has used to print parts for me in the past to diffuse light from LEDs.

When I started with ABS, to save time, I bought a pre built wade extruder from Wolfgang and this has served me well. However, I've heard on the grapevine that this design needs to be thoroughly cleaned with acetone before it can be used for PLA if it has previously printed ABS.

Being lazy I simply ordered a second extruder. Wolfgang's parts are top notch. I have a lathe and could make extruder parts myself but for the price he charges I can't be bothered.

I initially tried printing a 10x10x10mm cube. This came out OK but sagged in the middle. The reason for this was that I had created the gcode previously for a 0.4mm layer height, and my new extruder has a 0.35mm nozzle.

I re-skeinforged(?) the STL with a layer height of 0.25 (~=0.35 * 0.8) and printed some LED diffusers that I had designed. They all warped at the corners:

The temperature I used for this print were:
Extruder = 220C
Bed = 55C

My PLA is 4043D and has a lower melting point so I reduced these to
Extruder = 200C
Bed = 50C

My wife makes greetings cards as a hobby. She has previously bought kits where a pre-cut card is supplied with paper to layer behind the card. They look quite nice:

She asked me if I could print a template to allow her to cut the card herself. To do this, I photographed the card, then used GIMP to convert the wine glass shape to be pure black.

I then imported this image into AlgoLab Photo Vector and converted the image to a DXF file.

I then imported this to CreoElements and from this I was able to scale the design to match her requirements and print a template she can use for cutting:

Dome Goal

2011-08-07T13:59:00.000-07:00

I got my homemade Milestag UMT board working this week. This has forced me to think about acrylic domes again. I bought 4 pairs of acrylic domes from LasertagParts whilst in the USA last year, but now I've used them all.

As mentioned previously my neighbour made me some dome molds from a weird slate/resin composite. These are just right but I needed to create a hole in a sheet of wood to allow me to force the soft acrylic sheet around the mold.

The problem I had was that the outer diameter of the mold is 36mm and the nearest hole saw I have is 44mm. A 44mm hole is too big to force the soft acrylic sheet around the bottom of the mold.

To solve this I drilled a 44mm hole in a sheet of 6mm MDF and then printed a bush to reduce the internal diameter of this hole. Here is the CAD:

And the printed part:

It has a flange at the bottom to prevent it from being pushed out of the MDF:

Top down you can see the diameter reduction:

I cut a second sheet of MDF to provide a flat surface to place the mold on. Here it is forcing 2mm acrylic, heated at gas mark 9 for 4 minutes, over the mold:

And with the forcing plate removed:

I'd previously sprayed the mold with PTFE to aid removal:

The molds have a threaded hole underneath. This allowed me to hold the mold in the vice whilst I gently prised the acrylic free. As this mold has a draft angle it came off quite easily:

The remaining problem was now the removal of the dome from the sheet. To do this I used my 44mm hole cutter on two 15cm square pieces of wood which I then placed on top of each other with the holes aligned. With the hole cutter in my drill press this prevents any downward force being applied to the dome, which might crack it. I applied very little force whilst cutting and I let the acrylic soften from the tool friction as this seemed to prevent cracking. I destroyed one dome by pressing too hard:

Here are sheet and dome after separation:

I cleaned the rough edges on my belt sander:

Here it is after grinding:

Total time is about 15 minutes, 4 of which is waiting for the acrylic to soften.

Can I repeat it? Of course!

DIY Milestag UMT board

2011-08-03T01:32:00.000-07:00

I managed to get some ISD1790SY sound playback ICs for my homebrew Milestag UMT PCBs.
I've spent the last couple of days populating the PCB and programming the sound chip.

This board will soon be available at Tagbits.co.uk

Whilst doing this my RepRap has been idle, so I printed this castle from Thingiverse just because I can.

It came out very well:

Iron sights

2011-07-30T14:38:00.000-07:00

I now have 4 complete RepRap'ed Milestag guns. The only problem is that I only have two optical sights available and my son and his friends were complaining about aiming the two sightless guns.

So I designed and printed some classic style iron sights. These are not ideal for the kids as they take a bit of effort to use but they are better than nothing.

Here is the sight after printing:

And attached to a Mk3 Milestag gun:

I've been letting my son use them as he and his friends are an excellent test of robustness, the only casualty so far was a sight mount that I have since reprinted at 100% fill. Here they are all tooled up with Mk1, Mk2 and Mk3 guns. All gun bodies are entirely 3D printed except for barrels (20mm conduit) and the optical sights.

Dome Mounts Finalised

2011-07-20T00:24:00.001-07:00

In previous posts I've shown how I used velcro to fasten the Milestag sensor domes to baseball caps. I originally started sewing these in place, but my wife saw what a mess I was making and did it properly for me.

The problem is that as I print more Milestag guns she hasn't got the time to sew all these velcro patches in place, so I had to look for an alternative method.

Initially I tried fabric glue. At first this seemed promising but failed completely when the caps got wet. I decided to try snap fasteners. These are frequently used on boat and convertible car canopies, and can be held in pace with with rivets or screws.

I designed a new RepRap'ed dome mount with placements for two fasteners held in place with short self tapping screws:

I used two fasteners to prevent the domes from rotating. Here it is with the sensor PCB in place:

This is a much faster way of attaching the domes. No sewing or waiting for glue to dry. It takes about 3 minutes to punch a hole and rivet the stud to the cap.

Mk3 Final Parts

2011-07-16T16:01:00.000-07:00

I printed the final parts for my RepRap'd Milestag gun today. It's a muzzle flash suppressor modelled on this sort of design.

Here is my suppressor design after painting matt black:

The Milestag circuit drives a high intensity LED for the muzzle flash, but this sort of design needs to diffuse the light from the LED along the suppressor.

I've used PLA successfully in the past for this purpose, but I'm unable to print PLA at this time so Nophead kindly agreed to print me my design:

I've also managed to find time to fully assemble the gun:

Here is a video of the flash suppressor

Angle of attack

2011-07-08T15:51:00.000-07:00

This week I've been printing the Mk3 version of my RepRap'd Milestag gun. This version is only aesthetically different from the Mk2 in that it has a tapered barrel mount with dummy barrel cooling:

The RepRap challenge here is the tapered section. I need to print this part:

There are 3 ways I can do this:

1. Vertically

The problem here is that there are several sections that are orthogonal to the Z axis. The only way to print these is to have either support material or 45 degree angles leading up to them. Both are wasteful and time consuming.

2. Support material

I could chose to print the part with support material. This will of course take longer and use more ABS filament.

3. Rotate the part

I decided the best way to print this was to rotate the part so that the largest surface was parallel to the bed.

I had concerns that the edges or the faces orthogonal to the barrel axis might not mate very well. I was not disappointed:

Here you can see how well the faces that were angled to the bed match up:

Picatinny

2011-07-04T14:01:00.000-07:00

This weekend I printed a Picatinny rail sight mount for my Reprap'd Milestag gun. It came out very well thanks to the engineering drawings on Wikipedia.

Here it is hot off the printer:

Again I cleaned the ABS with MGR before spraying. When I printed the gun main body, I placed four holes to align with the holes in the rail mounting plate, but the holes are covered by about 3 layers of ABS. This allows me to have an unblemished gun body if I decide not to fit this rail.

To fit it, I simply align the plate and screw #4 self tap screws through the plate into the gun body, they pierce the first 3 'blanking' layers then engage in the holes.

Here is the rail fitted to the gun with a red dot optical sight:

Dome Sweet Dome

2011-07-02T14:35:00.000-07:00

Today I completed the IR sensor dome for my ReRap'ed Milestag gun. The standard Milestag domes are supplied with base and dome sections.

The method of joining the base to the dome is undocumented, but most seem to end up gluing them together. I don't like gluing several GBP worth of electronics into an inaccessible housing, so I printed myself a new base for the dome. This has a mounting pillar to fit the homemade Milestag sensor PCBs that I designed. It also has 3 screws to fasten the dome to the base so I can disassemble the sensor when required.

Here is a picture of the sensor PCB and the dome base/fastener washer that I printed:

Here is the sensor PCB fitted to the dome base:

The dome base has three holes for #2 x 6.4mm self tap screws. These fasten the acrylic dome to the ABS base:

Here is the fully assembled unit. Note the two self tap screws on the LHS/RHS of the dome:

Paint it Black

2011-07-01T00:34:00.000-07:00

Last night I printed the final part for my RepRap'd Milestag gun. It's the end piece for the muzzle designed to look like a flash suppressor. Inside it is a rod of PLA printed for me by Nophead. This has a high brightness LED fitted inside to diffuse the light along the length of the rod.

In this picture you can see the muzzle end with the PLA rod on the left:

Over the last few days I've been painting the ABS body and installing the Milestag electronics. I've found the best way to paint ABS is wipe it with a lint free cloth with MGR. I had this left over from my high pressure water gun project and it cleans ABS and PVC equally well.

I then sprayed it with matt black paint I got from a local car spares shop. It looks pretty good now it is all together:

Here you can see the LCD panel, speaker holes and battery cover:

And a close up of the flash suppressor with the LED diffuser fitted:

I now need to build the head IR sensors then it's done.

Ready to build

2011-06-24T00:37:00.000-07:00

All the components of my Milestag lasertag gun are now built. I'm going to add the electronic modules and build it this weekend.

More big time

2011-06-22T00:31:00.000-07:00

Printed the second half of my Milestag gun body last night.
This part incorporates the speaker mount, LCD display mount, a hole for the reload switch and battery compartment access.

Big Time

2011-06-21T00:26:00.000-07:00

Last night I managed to successfully make my biggest part yet. It is the RHS body of the milestag gun housing and has placements for battery, RJ10 connector, key and mode switches. It has printed very nicely indeed. Each corner has lifted slightly but this is unsurprising as there is a 45 degree chamfer on each edge.

Here is a picture:

and from above:

and with the parts fitted:

Trigger Happy

2011-06-16T14:13:00.001-07:00

I've just finished printing the handgrip and trigger for my Milestag gun. The trigger slides on a raised section on one of the halves of the grip. It's a bit tight and I need to reduce the size, but I've managed to make it slide by sanding the trigger down and lubricating it with PTFE spray. Three self tapping screws hold the two halves together and there are four holes to mount the grip to the gun body.

Gutenberg in the third dimension

2011-06-09T14:05:00.000-07:00

The more I use my reprap. The more impressed I am. The results are spot on and easily outstrip the speed and quality of manufacture that I could acheive machining the parts by hand (even if I had the machine tools to do so).

Here is the CAD drawing of the barrel holder/focus tube holder part of my gun model:

And here is the real thing as printed by reprap:

Assembled side on:

And the real thing:

From another angle:

Dome Moulds

2011-06-08T13:48:00.001-07:00

I mentioned that I was trying to make Milestag acrylic domes to my neighbour who reminded me that he was a pattern maker and with a 'leave it with me' off he went.

Today he turned up with these:

6 dome moulds with a 3 degrees draft angle. All I need to do is fasten them to some plywood (supplied) and drill some forming holes.

They are made of a wierd material made from a composite of Welsh slate and resin.

Can't wait to try them.....

Lasertag Gun Mk2

2011-06-03T14:26:00.000-07:00

I've started designing a new lasertag gun using CoCreate. The last one worked well, but could have been improved on several points:

1. I designed the last gun for 4 batteries, not 6. DOH!
2. The gun was far longer than it needed to be as the focal length of the lens was only 55mm.
3. The lens did not fit very well into the ReRap'ed housing due to the layering.
4. It was too tight a squeeze for all the internal components.
5. I put cable holes as semicircles in each half of the casing. This resulted in cables becoming trapped during assembly.
6. No sight mounting holes.
7. The grip was too wide.

So I've re-designed it using a shorter barrel section and added some curves. Still work in progress but it is looking good so far:

Fully Focused

2011-05-30T14:23:00.000-07:00

Nophead kindly helped me to get my RepRap commissioned last week. I've been building it now for about 5 months and I was pleasantly surprised when it sprang into life. Thanks to Nophead for all the help!

Anyway, I've been looking into designing an IR focusing tube to fit in with the modular gun design that I am working on. I wanted a unit that would bolt together with a few screws and allow accurate focusing of the IR beam. I also need the design to be flexible enough to fit on different gun designs.

Here is my first attempt:

It is a 6 part assembly comprising of a lens retaining ring (red), the lens (blue),
focusing tube (grey), IR led mount and slider (green), focus screw mounting plate (purple) and focus screw retaining plate (yellow).

The plates are fastened with 2 self tapping screws which are not on the model. Also, the focusing screw is not shown.

Here is a picture of it assembled:

There is a 6mm 'bar' at the top of the tube allowing the tube to be fitted inbetween 6mm MDF sheets when using an odd number of sheets in a gun design. This could easily be increased to 12mm for even numbers of sheets, or a multiple of 9mm if sheets of that width were used. Two holes in this bar allow an M4 bolt to hold the tube in place.

I printed the whole thing this weekend, and after an aborted print caused by the plastic getting too hot due to bad thermistor connections I got this:

A view from the top of the lens tube with the LED mount above:

Here it is assembled:

From the back you can see the self tapping screws holding the focusing screw plates in place and the encapsulated head of the focusing screw:

And from the front showing the LED mount in place through the lens:

I'm more than pleased about the way it has turned out. Just need to modify my gun design to use these then I can start knocking them out!

Dome Again!

2011-05-07T06:05:00.000-07:00

Today I had another go at making acrylic sensor domes. I've given up on vacforming as acrylic is not malleable enough to form properly this way with the equipment I have.

Instead, I decided to try press forming. This process involves heating the acrylic to make it soft, then pushing a tool into the sheet to make the desired shape.

As a test I made a simple cylinder out of two layers of 12mm MDF that I cut out with a holesaw. I fastened them both with a woodscrew to a base:

I fastened an a6 sheet of 2mm acrylic in the clamping plate I made a few weeks ago, and heated it under the grill. This was my first error, the grill is too fierce and the acrylic started to bubble. I tried it anyway as it had gone soft.

The plan was to use a piece of MDF left over from cutting the cylinder. This is about 2mm larger diameter than the cylinder and I used it to force the soft acrylic sheet over the tool.

Here's a picture after the operation. The MDF sheet used to force the acrylic is on the right.

It worked quite well, but as I had not put a draft taper on the tool, I broke the acrylic trying to remove it:

It occurred to me that the metal frame was not really necessary for this method of molding, so I made tried again with a new sheet of acrylic. This time heating it in the oven (gas mark 9, 5 minutes at the top) placed on the MDF sheet used to force it over the tool. I also smeared some vaseline as a release agent onto the cylinder.

Here's me waiting for the acrylic to harden:

With the forcing plate removed:

It was still difficult to remove the formed piece afterwards, but it did come off:

I then used the same sized holesaw to cut the piece out from underneath:

Much better than my vacforming attempt. Here's what I learned:

1. Draft angle is essential.
2. Use oven at high heat and time the heating process.
3. Don't use a grill!
4. Forcing plate makes all the difference.

I'm going to try again soon with a better tool. I think that will result in a dome that I can use.

DIY UMT

2011-05-05T14:20:00.000-07:00

My Milestag UMT PCBs arrived from China today. Just under 14 days since I placed the order with them. Not bad. The quality is good with holes centered well on pads, and for about 25UKP for 10 boards, inclusive, they are a bargain:

I just need to populate them. Bit busy with RepRap at the moment though...

More Sensor Housing

2011-04-23T02:56:00.000-07:00

I'm still trying to find a way of making sensor domes from acrylic sheet. After my last attempt destroyed an A4 sheet trying to make just one dome, I made an A6 clamp so I can make 4 domes per A4 sheet:

I still need to make a mold.

In the meantime, I discovered these:

On the left is a single seedling propagator that can be bought at gardening centres. They are not as hard as acrylic, but compared with the milestag dome on the RHS they are just about the right size. The flange they have at the bottom also makes for easy mounting.

They may be of use to someone....

DIY Milestag UMT boards

2011-04-22T01:55:00.000-07:00

Some time ago I decided to design my own version uf the Milestag UMT board but using components easily sourced in the UK.

I used KiKad to re-engineer the UMT schematic:

And designed a PCB using surface mount components. The PIC micro is through hole so it can be taken out for re-programming. I could have put a programming header on the board but I decided not to as it would have made the board bigger:

I've sent the gerber files to Itead Studio for manufacturing. They charge only $28 + $5 delivery for 10 boards which must be the cheapest service on the planet.

I have no idea what quality they will be, but for a $32 punt it's got to be worth a try.

Dome, on the range

2011-04-10T13:17:00.000-07:00

Whilst awaiting my RepRap extruder to be delivered from Germany I've re-visited vac forming.

I made a new clamping frame from 1.2mm steel, and used M4 dolts + wingnuts to fasten it:

I also drilled some more holes in the bed of my vac former, and attached sealant gasket gasket to the bed to improve the seal:

I made some molds by casting plaster of paris into the acrylic domes I got from Milestag:

Here's the molds after they had set:

Unfortunately, this was no more successful with 2mm acrylic than it was with 4mm. The problem is that the acrylic is not sufficiently flexible to be sucked completely into shape by the vacuum. The plastic failed to form around the vertical edges of the mold.

So I decided to try another approach. I constructed this phallic object:

The idea being that I push the frame down around the mold, I should be able to exert more pressure than the vacuum.

Here's the result:

And after cutting:

Which is almost what I want. To improve I need to:

1. Change the mold so that the acrylic can't fold underneath the mold. I'm thinking of a wooden pole with a rounded end.

2. Make the frame smaller. I used an A4 frame this time, but to make just one dome it's a bit too big.

3. Cut the dome out with a power saw. I used a hacksaw and cracked it.

This sucks

2011-03-29T14:32:00.000-07:00

I tried my homemade vacforming machine last night with disappointing levels of success.

I drilled a 32mm hole in the side of the box and attached my DeWalt shop vacuum.

I then clamped a sheet of 4mm acrylic into the holding frame

and placed an inverted ceramic pot on the vac bed as a test pattern:

And placed the sheet in the oven at gas mark 8 for 10mins. I was hoping to observe the sheet and, when it started to sag, remove it. The problem I had was that the sheet was too thick and didn't get hot enough before the MDF mount I was using started to char.

As the kitchen filled with the smell of cooking MDF I decided to give it a try anyway:

The thick, partially heated sheet was sucked down by the bed but was not hot enough to be pulled down onto the sides of the pattern. As a result I got this:

I also noted that the MDF mount had shrunk and was no longer gripping the sheet.

Next time I am going to:

1. Use thinner 2mm acrylic.
2. Make a metal mounting frame which will neither shrink nor smell.
3. Drill some more holes in the bed.

Going to be a while before attempt 2, my RepRap bits turned up today ;o)

Killing time

2011-03-27T13:32:00.000-07:00

Whilst I am waiting for some parts to arrive for my RepRap, I found myself with an hour spare and decided to try making a vac forming machine.

It has a small footprint and is made from 12mm MDF. The clamping frame to hold the plastic sheet is 6mm MDF held together with 8xM4 bolts.

I haven't had chance to try it yet as I don't have any plastic sheet. We used to have a vac form department at work years ago but they outsourced it, so no free test sheets from there.

I intend to use it to make the domes for the Milestag sensors from acrylic sheet used on greenhouses.

Here are some pics:

Here is a side on view showing the clamping plate:

Finishing Touches

2011-03-25T14:29:00.000-07:00

I completed the sensor head mounts this weekend. As I showed here I fastened hook velcro to the sensors. I attempted to sew some 50mm loop velcro to a camo hat I bought from Blue Moon Guns of York for £1.99. But after 30mins of inept stiching my wife caught me and with a Bradford 'give it 'ere' she managed perfection in 15 minutes what took me 30 to ruin:

Here's the complete system. I still need to cover the connecting PCBs on the hat and wire from the gun but I'll make some enclosures to do that when I've got my RepRap built:

Sensor testing

2011-03-04T12:48:00.000-08:00

Today I tested my homemade sensor PCBs. I had made a mistake with the connecting curly cable in that the leads were reversed. I fixed this by simply reversing the connection order at the gun end PCB.

Here is a video of the test showing shot detection and hit LED activity@

The Last Parts

2011-02-21T12:46:00.000-08:00

I completed the sensor connection PCB this weekend. I need to cover it with heatshrink to protect it but I need to test the full system before I can do that. Here it is connected to the gun complete with curly cable leading to the sensors:

Here is the complete assembly:

To test the system I need to construct another Milestag PCB. As mentioned before I bought 4 of these so I used my PCB jig to help me populate the boards:

This device holds multiple PCBs, allowing me to place components. When populated, a foam covered board is placed over the components and clamped in place. The jig then rotates to allow the components to be soldered whilst the foam prevents them from falling out:

Here are the completed boards:

I intend wire IR LEDs and trigger switches to the boards so I do a quick test. Before I can do anything with the remaining boards though I need some more gun housings, and for that I need my own RepRap......

Completed Sensors

2011-02-06T13:44:00.001-08:00

Today I attached the two sensor housings to the new RJ10 PCB I made. Here is a detail of the junction PCB showing the two sensor leads attached with tie wrap strain relief:

Here is the assembly showing the two sensors attached:

I decided to attach the sensors to clothing with velcro. This allows me to flexibly configure the sensor positioning as required. I bought some 50mm velcro and stamped holes in it to allow me access to the sensor screws.

I've also designed a small PCB to hang from the gun to allow me to connect a RJ10 curly lead to the sensors:

I just need to make this and the gun is complete.

Sensor Connections

2011-02-03T14:49:00.001-08:00

I've been trying to find the best way to mount the Milestag sensors to a headband and connect them to the gun.

I've decided that I'm going to mount a loop strip of velcro on a baseball cap or elastic headband and attach hook velcro to the back of the sensors. This gives me the most flexibility for sensor placement.

I've been unhappy with the way the sensors connect. They are traditionally soldered in parallel with a connection to the gun. I had concerns about the reliability of this as soldered connections break when flexed.

I decided to compromise and designed a PCB to connect two sensors to a RJ10 socket. Why RJ10 when others are using RJ11? Because RJ10 curly leads are available for less than 1UKP and these are ideal to connect the sensors to the gun.

Here is the headband sensor schematic:

It's very simple. I intend to place it in a small, velcro mounted box.

Here is a set of 8 PCBs ready for cutting and drilling:

Finishing the sensors

2011-01-23T13:19:00.000-08:00

Today I drilled my sensor PCBs. There were only two hole sizes, 0.8mm for the TSOP IR detectors and cable holes and 0.6mm for vias.

I use high speed tungsten drill bits with this 10000rpm PCB drill I blagged in a broken state from my previous employer:

I just populated two boards, which is sufficient to complete one gun. Here are the boards, one enclosed in a transparent sensor dome:

The next step is to mount these on a headband and connect them to the gun.

Milestag sensor PCBs

2011-01-22T13:27:00.000-08:00

As I've mentioned, I was fortunate to be in the USA last year and was able to get an American friend to order Milestag RevH PCBs for me, which saved me about 35UKP on postage. However, Jim was out of stock of sensor PCBs at the time. So I still needed to source these.

I decided to make my own. First I used Kicad to implement the simple schematic published on the Milestag site:

Then I designed a PCB around it. As I intend to make this myself, I changed the diameter to 31mm as this is the internal diameter of the 35mm holesaw that I have, and I replaced the two through hole resistors with surface mount ones to give me some more real estate to work with. Here is the design:

I repeated this 8 times onto an area of 160x100mm which is a standard dual layer size supplied by Maplin.

I then printed the top and bottom layers onto tracing paper with my laser printer:

The top layer is cut and overlayed onto the bottom layer. I align them using a lightbox to make sure the alignment is as accurate as possible:

When aligned, I fastened them together to form a pocket using cellotape and inserted the pre-sensitised PCB, fastening it with tape to prevent it from moving:

I then exposed the PCB to UV light from a single sided UV source, turning the board to expose the other side.

I develop the PCB with commercial developer, in the past I have used 99% sodium hydroxide crystals but this is nasty stuff. I got this from Mega Electronics. They do commercial grade PCB stuff but are willing to deal with individuals:

I etch my PCBs in a home made tank:

It's tuppaware with tropical fish tank heater and air pump with a wooden surround. Basic, but it works. God help me if it ever leaks though:

Here is the etched PCB:

I then cut each unit out with the holecutter:

After cleaning with wire wool, I used this stuff from Mega Electronics:

To tin plate the copper tracks to prevent oxidisation.

Here is the finished sensor PCB:

Full assembly

2011-01-16T14:37:00.000-08:00

I experimented with IR focus and the results were interesting. The circuit published in my previous post could detect IR from the gun at about 50m without a lens to focus it. My plan was to get as far away from the test circuit as I could until it failed to detect a transmission, then adjust the focus until the sensor saw the IR pulse again, then move further away.

Unfortunately, I was unable to get far enough away from the sensor in my test environment! I resorted to the IR camera and got a satisfactory beam focus by visually examining the size of the beam on my monitor.

I haven't built the IR sensors yet, but I decided to build the milestag gun up fully. It went together well. I also fitted a picatinny rail to the top of the gun and fitted a cheap red dot sight I got from ebay.

It looks pretty good. Trouble is, I now need to paint 60% of it bright orange to conform with UK imitation gun laws. Ah well.....

Focus, focus, focus

2011-01-15T15:06:00.000-08:00

I've been trying to optimise the focus of the Milestag IR beam today. At first I thought the best way would be to observe the beam, and try to get the brightest dot at the furthest distance.

To achieve this I created this unholy device:

This is a super sensitive IR camera with a battery powered CCTV alignment monitor + the Milestag IR focusing section of my gun with faux reload and trigger switches.

My idea was to see how far I could get the beam to be a minimum diameter.

It worked very well, except that at the distances I want I could hardly detect the IR light on the small monitor.

Also I looked a bit of a cock as I walked about my street in darkness with this thing.

So I sat back and thought 'what am I trying to achieve?'. Answer: IR reception at maximum distance so I came up with this:

It's the TSOP4856 detector the Milestag system uses connected via a transistor to a LED. When it detects a 57kHz IR signal the LED illuminates. With the aid of a helper I should be able to optimise the IR focus. The further away the LED lights, the better the focus.

Here is the test circuit built up:

Starting Assembly

2011-01-12T15:03:00.001-08:00

I started assembling the breech section of my reprap Milestag gun today. It was quite a squeeze to get all the components in, but they did fit.

Here is the system powered up:

The next stage is to fully assemble the breech and barrel sections and adjust the IR LED focus.

Baud to tears

2011-01-09T15:07:00.000-08:00

I was hoping to get the complete milestag gun assembled this last week. But before I could finish it I needed to program the ISD1790 sample playback chip which is present on the milestag PCB.

The ISD1790 has A/D and D/A converters, and FLASH memory to allow it to record and playback up to 90s of audio as 8kHz mono samples.

The IC also has an SPI interface to allow microprocessor control.

The milestag RevH core software has a mode to allow this IC to record audio played through a PCs line out socket. All that is required are an RS232 lead to the milestag PCB and an audio connection from the PC to the PCB.

This caused me no end of problems. I constructed RS232 and audio leads as specified in the RevH manual.

During the record phase, the ISD1790 board routes the audio input pin to the audio output pin so you can check the sample quality through the target speaker.

Putting the RevH mode into sound record mode did this, but the PC sound recorder software supplied did not force the sounds to record on the RevH board.

I checked all connections to no avail.

I then got back to basics and checked the PIC oscillator frequency with a scope. The PIC software is written to work at a particular frequency, and the RS232 baud rate it uses to communicate with the PC is a function of this frequency.

The scope showed that the clock was not running at all. I read the PIC memory with my ICD2 and this showed that I had set the PIC clock config byte incorrectly. This meant that the PIC was being clocked at 4MHz instead of 16MHz.

The result of this is that the PIC was expecting data from the PC at 2400 baud instead of the 9600 baud the PC uses.

I reprogrammed the PIC with the correct oscillator config and the sounds recorded successfully.

During all the plugging and unplugging I managed to damage the LCD display so as as soon as I have a replacement I will complete the build

It Lives

2011-01-02T15:25:00.000-08:00

I programmed the PIC 18F2525 MCU today. I've been working with PICs for a long time and I am fortunate to have a Microchip ICD2 programmer/debugger. I extended the wires from this to allow me to program the MCU on breadboard:

I wanted to attach the LCD module to the RevH board using an IDC connector to minimise soldered connections. This is where I encountered one of several unsatisfactory issues with the Milestag RevH design. The LCD connector has been CADed so that odd and even pins are swapped in relation to IDC connectors.

i.e. Pins 1 & 2 are swapped, pins 3 and 4 are swapped.

This prevents using a female IDC connector at the RevH PCB end and a male one at the LCD end. I was forced to solder the leads to the LCD with the pins swapped.

Once this was done, I powered up the board. I initially thought it was dead as nothing appeared on the display but on closer inspection, the LCD was displaying:

COMBAT
T.A.G

but very faintly. Issue 2 with the Milestag design is that the LCD contrast is set with 2 fixed resistors. This is fine when using the stock Lasertagparts LCD module but I got mine from Ebay priced 2.87UKP including delivery.

The Milestag schematic uses two fixed value resistors to form a potential divider to set the LCD contrast. I had no idea what values were required for my LCD module so I swapped the 17K resistor for a 2.2M pot and tweaked it until I got an acceptable result, then measured the pot resistance which came out at 175K. I upped this to 180K. This really should have had a trimmer on the PCB to simplify this for none stock LCD modules.

And so it lives:

Getting to the core

2010-12-31T15:03:00.001-08:00

As I've now completed the Reprap'd gun casing I've turned my attention to assembling the Milestag RevH core module PCB. I got these delivered from Lasertagparts to a friend in the USA and brought them back with me whilst on a visit, which avoided significant postage fees (not sure why the postage is significant, they are small and light).

All the electronic components arrived in time for Christmas from Farnell, Mouser and DigiKey. I've had to buy a lot more bits than I require but I intend to make more than one unit (of course!).

I've not assembled any totally through hole PCBs for a while, my last 2 projects were surface mount but I have these to help me with the axial components:

They produce perfect, 90 degree, repeatable bends on axial leads thus:

Which significantly speeds up the assembly process.

I had an problem trying to order 2x3 and 2x2 0.1" headers required for the LCD interface on the PCB. I just could not get them so I doubled up a strip of single 0.1" header that I had lying around cut to 2 pieces of 1x3 and 2 pieces of 1x2.

Here is the assembled PCB:

The next step is to program the microcontroller.

Painting and decorating

2010-12-27T15:07:00.000-08:00

Over the Christams holiday I've attempted to fit all the housing hardware and paint the case.

To paint I first cleaned each part with solvent, then sprayed with a silk finish, solvent based paint. This seemed to bond very well, as you would expect.

I then attempted to fit the 3.5mm jack socket I plan to use for the RS232 interface. But the hole I had recessed in the CAD design was not wide enough to accept outer diameter of the socket, and the depth of this recess was insufficient to allow the threaded end to protrude enough for the mounting nut.

This was a problem as this hole is inside the housing and there is no clearance for a drill. I could not drill into the housing from the outside as I neede to maintain a 6mm hole to mount the socket.

I eventually widened the hole by heating a short M10 bolt and by holding this in mole grips, I melted the hole to be the correct diameter and depth.

Here is the casing with the jack socket fitted:

I laid out all the parts with hardware fitted. Here is a detail of the LED focus mount.

And its place in the barrel section

Here is the barrel, IR LED, muzzle LED wiring, mode switch, power switch and trigger from the inside

And from the outside

The LCD display, speaker, battery, battery cover and reload switch from the inside

and outside

Everything seems to fit. I've got all the electronic parts for the REVH board. All I need to do now is build the core module

Costs

2010-12-23T14:52:00.000-08:00

I've been asked how much the plastic costs to manufacture one of these milestag gun housings. After a rather inebriated afternoon at the company xmas do with nophead he told me that the ABS filament he uses costs 2p per gram. The weight of my gun parts is 522g = £10.44UKP for a single gun housing. This compares very favourably with airsoft guns which cost £140+ in the UK and still need to be engineered to contain the MILESTAG electronics.

My design is custom engineered to fit the stock milestag electronics so there is no cutting, gluing, drilling required.

Barrel stays

2010-12-22T14:18:00.001-08:00

My design for a RepRap MILESTAG gun requires that the barrel is prevented from rotating about or sliding along its axis. Sliding would result in the barrel becoming longer or shorter which is obviously ridiculous. Rotation is a problem when there are attachments to the barrel (such as my aesthetic flash suppressor) or muzzle flash LED wiring.

I originally designed two rings, one of which had small tabs which mated with the barrel housing to prevent rotation. These tabs were woefully inadequate and I snapped one off whilst installing the barrel.

Here is a picture of the two rings installed. Note the small (i.e. inadequate) tab on the right hand side barrel ring.

I redesigned the holding brace and nophead printed it to his usual high standards:

And here it is fitted.

Full assembly

2010-12-18T14:01:00.000-08:00

I managed to assemble the complete milestag gun housing today and I've had to address a few issues whilst doing so.

Here is a picture of the completed gun housing

And another showing the mounted lens

As mentioned in my previous post, the recessed radii I use to mount exisiting circular objects (e.g. lens, barrel) were imperfect so I had to use a half round file for the barrel mounts and a Dremel with a bur for the lens mount.

Secondly, the RepRap'ed parts are not perfectly square and made worrying cracking noises as I tightened the self tapping screws. Upon disassembly I noticed that some of the plastic layers had detached from their immediate neighbours due to the stresses of straightening out the housing as the screws were tightened.

I've managed to repair the damage with ABS solvent and this seems to have generally strengthened the parts as the layers are all now fused together (on the outer surfaces at least).

I believe that the ultimate solution to this is to sand flat any imperfections on a linisher before assembly.

The next step is to paint the ABS with a solvent based paint and fit the electronics.

Last piece(s) of the jigsaw

2010-12-17T15:05:00.000-08:00

nophead kindly delivered the last pieces of my milestag gun housing today.These are the fittings and fixtures that make it work:

Here is the aesthetic flash supressor that fits on the end of the 20mm conduit barrel

The trigger fitted to the previously presented grip

The battery cover

The LED focus mount and aligner

The barrel alignment rings. These stop the barrel moving along the axis of the gun and the tabs are intended to stop the barrel rotating

These are 2 x LED diffusers not on the original CAD drawings. They are made from translucent PLA and are designed to fit in the end of the conduit barrel to mount and diffuse the muzzle flash LED

I started assembling the grip and breech this evening. I used #4 x 19mm self tap screws to bring the housing parts together. I had several problems with my design:

1. The holes the screws were to screw in to were too small. The self tap screws are imperial size #4 x 19mm with a diameter of 2.88mm. Some testing with scrap plastic showed that a hole of 2.5mm was best and I had to drill all receptacle holes to this diameter.

2. I had not sufficiently countersunk the mounting holes on the breech section. Subsequently the self tap screws did not protrude from this part. I had to increase the countersink depth by 12mm.

3. Several of the parts of this design require a 'sliding' fit. i.e. the trigger and the LED focus mount. I had CADed these to exact dimensions but RepRap seems to make things slightly bigger, and the ridges caused by the layer extrusion tend to interlock so these parts needed to be filed.

4. The small tabs on the barrel rings are meant to prevent the barrel from rotating but they are too small and will easily snap off. I need to thicken them up in the next revision.

5. The barrel and lens mount radii do not fit the 'perfectly' rount barrel conduit and lens. This is because RepRap extrudes layers of a finite size which results in a imperfect circle. The result of this is that the halves of the housing do not meet properly where there is a diameter between them (i.e. the barrel section, the flash suppressor). These parts currently require sanding. I believe that I need to increase the radius of these radii to fix this. Really need to do some empirical testing.

6. On several parts I had not allowed sufficient clearance for the head of the self tapping screws. A minimum of 5.5mm is required for #4x19mm screws.

Here is a picture of the assembled breech section complete with grip

And the LED focus mount in position

Assembly

2010-12-17T00:59:00.000-08:00

I ordered the electronics for the Milestag RevH board yesterday. It was rather expensive as not all parts are readily available in the UK and I was forced to pay 12UKP shipping charges.

As soon as the components arrive I'll be able to complete the gun.

nophead delivers!

2010-12-14T15:15:00.000-08:00

nophead has been busy working on my Milestag prototype this last few days and the results are impressive. All the large parts have now been printed, all that remains are a few ancilliary components such as the trigger, LED mount etc. See my previous blog entry for the CAD pictures that produced these parts.

Here are some pictures:

The main gun sections:

One side of the barrel section fitted with 20mm conduit barrel:

The 'breech' section with LCD, speaker and reload switch:

The outside of the breech showing speaker holes, LCD and reload switch:

Handgrip sections with microswitch in position:

Barrel section with lens. Also shows focusing rail:

And finally, assembled breech and handgrip:

Milestag

2010-12-09T14:22:00.000-08:00

My 8 year old son Joshua and I went to Flamingoland for his birthday and had a go at 'Crazy Combat Laser Battle'. We both had a great time and this got me thinking.....

The system they use is MILESTAG a sort of open source 'Laser Tag' system. I was already familiar with the system and my encounter with it was the catalyst I needed to make my own.

I ordered PCBs and plastic domes from www.lasertagparts.com and had them delivered to a friend in the USA I was about to visit. There was a slight problem with the order but a quick 'phone call to the site operator Jim sorted it out.

It occurred to me that the majority of the work required to get a working system involved manufacturing a gun housing, or buying an existing (e.g. Airsoft) gun and modifying it.

I've been monitoring the RepRap movement for a while and it seemed to me that it would be a good medium to build a gun housing with.

I've known nophead for far too long and he very kindly agreed to use his 3D printer to manufacture a custom Milestag prototype for me.

I used CoCreate personal to design the housing. It includes battery compartment, grip, microswitch trigger, lens mount, adjustable IR LED mount, PCB, speaker, LCD, RS232 , mode/reload switches in one modular unit.

Here are some pictures of the whole gun, complete with aesthetic flash suppressor:

Here is a picture of the lens mount and adjustable 5MM LED mount. The lens is a standard 32MM plano convex unit from Surplus Shed and the LED can be adjusted to obtain the optimum focal distance.

This last image shows the speaker/LCD mount and reload switch:

Here is a 'proof of concept' 3D print of the CAD image above. It is damn close to perfect. Going to hassle nophead for the rest soon.

This is my first ever attempt at 3D CAD so I'm sure the next version will be better.

More solenoid valve tests

2010-06-20T12:32:00.000-07:00

I manufactured a custom nozzle to fit directly onto my 1/4" solenoid valve and decided to photo document the nozzle manufacture procedure.

I started with some 20mm Delrin bar

I then turned this down at one end to allow me to tap it to 1/4" BSP at 19 turns per inch with is a standard pneumatic fitting in the UK.

I then applied a thread to it with a die that my Grandfather left me.
I held the die by hand with the work piece in the lathe chuck. I turned the chuck with the chuck key.

Ironically, I was applying a British Standard Pipe thread with a die that was made in the USA.

I then put a chamfer on the thread to ease starting the thread

The next stage was to drill a 2.5mm hole through the nozzle

And added a taper to reduce the internal diameter from 1/4" to 2.5mm

I then added an external taper using the lathe cross slide at an angle

Here is the finished nozzle

Here is a video of the solenoid valve in use

The trigger is very responsive but as I experienced last time, the range is greatly reduced. I got about 28 geet out of this test. The problem is that the solenoid valve has a restricted inlet port and this is where the problem lies.

I've decided to give up on solenoid valves. They are OK with air but water is too viscous. Ball valves are the way to go, but automating them could be a pain.

However, I do have some experience with pneumatics, and I have a tank full of compressed air on my back.......Watch this space.

Rapid Fire

2010-06-14T14:42:00.000-07:00

I tried controlling the water flow with a solenoid valve this weekend with mixed results. I wired it to a 12V battery pack via a push button switch I had lying around.

The valve has 1/4 inch BSP inlet and outlet fittings, yet my pipe and nozzle are 3/8 inch BSP. I had to get some adapters to reduce for then expand from the valve. They can be seen as the silver fittings on each side of the solenoid valve.

The valve worked perfectly. I was able to rapidly turn the flow on and off. But due to the restriction from 3/8 to 1/4 at the valve inlet, and expansion from 1/4 to 3/8 at the outlet, plus flow resistance from the valve innards there was too much pressure reduction and the range was reduced to about 28ft.

I'm going to try a new nozzle turned to fit directly onto the 1/4 inch valve outlet next. Hopefully this will reduce the pressure drop.

Printed Circuit Board

2010-06-09T14:48:00.000-07:00

My adventures with Kicad continue. I was going to make the solenoid control circuit on a piece of veroboard but decided to use Kicad to design a PCB instead. I've recently moved from Windows XP to Windows 7 and my old electronics design software will not run without tweaking. As a result, this has become an exercise in PCB CAD package education as well as the water gun itself.

Here is the single sided PCB I've designed:

I'm not going to make it though until I have tested the water gun with the solenoid valve I have to see if it is suited to pulsed operation.

Water Control

2010-06-07T14:10:00.000-07:00

I still need to do some more experiments with nozzles, but in the meantime I have started on the design of a controller for a solenoid. The ball valve is somewhat unwieldy to use in practice, a trigger mechanism would be much better.

As I do not have access to a push button operated valve that is high pressure rated I'm going to use a 12V solenoid valve I got from ebay.

It is rated at 130PSI and so is OK for the pressures in my system.

I'm going to control it with a small micro controller so I can operate it in one of several modes:

Single Shot,
Three Shots Rapid,
Continuous Pulse,
Continuous Stream.

The trigger will be a push button switch and the mode changed with a seconds push button. The controller will indicate the new mode with audio feedback from a buzzer.

I'm using a Microchip PIC for this design as I am familiar with them and I already have all the development tools.

Here is the schematic drawn with the fantastic Kicad.

The power for the circuit will be supplied by 8 x AA batteries.

Empirical Testing

2010-05-30T15:00:00.000-07:00

I managed to find some time to do some nozzle tests today. I turned a nozzle with a blank end and gave it a 15mm-3mm internal taper.

I then drilled a series of progressively larger holes and measured the range for each hole diameter. I drilled holes in the range 1mm-4.5mm in 0.5mm steps. Here is a graph of the results:

From this I can see that 4mm is the optimum hole size (as I do not have any drills that are not multiples of 0.5mm this is as near as I can get).

However, as the last nozzle diameter was 4.5mm I had to make a new nozzle to get the diameter back down to 4mm.

So here it is, the final design which gives a horizontal range of 40ft with the nozzle at a height of 3ft above the ground.

I've not had chance to test the maximum range with the nozzle angled, but 40ft ain't bad. Next I need to test the maximum range with the nozzle angled and calculate the flow rate.

Heat of battle

2010-05-23T12:52:00.000-07:00

Incredibly as predicted the weather man got it right this weekend and it was a scorcher (for the UK 27C = 80F). As mentioned I managed to create a backpack harness for the tank. As I was rushed, I was unable to take detailed stage photos.

Here is a picture of the tank complete with backpack and newly fitted 3/8" tubing.

I had problems working out a way to create a harness. In the end I bought a cheap backpack and cut the 'bag' part away to leave just the shoulder straps and the part of the pack that rests against your back.

I then fastened this to a 16" wide piece of 10mm plywood. I did this by cutting three 2.5"x16" strips of 15mm pine. I placed the plywood on the bench, centralised the back of the backpack on the plywood then placed the three strips of wood on top, sandwiching the backpack material in between the strips and the plywood. I then drilled 4 holes through all three layers in each strip.

I then recessed each hole in the strips using a 20mm Forstner drill bit. This allows me to ensure the nuts and washers I used to bolt the three layers together did not protrude above the surface of the strips which, when in place, rest on my back.

Here is a close up of the back of the pack. The three strips can be seen in between the two black shoulder straps. Note the recessed holes for the fastening nuts and washers.

Using a router, I put a radius on the strip edges so they would not be unconfortable when wearing the harness.

To mount the tank to the plywood sheet I fastened two 1.25" planks together along their edge, then cut two 4" holes centered at the junction of the two planks. When apart, this leaves semi-circular holes for each tube to fit in.

When clamped together with bolts, this grips the tank quite firmly. Here is a top view looking down onto the top of the tank.

This 'clamp' was then bolted to the ply.

However, when loaded with water the tank is heavy, so I solvent welded two strips of PVC onto the outside of each tube. These rest on the 'clamp' above and prevent the tank from slipping through the holes. This also shows the backpack strip radius.

To fasten the tank at the bottom, I created another piece of wood with semicircular 4" holes and fastened this to the ply. The tank tubes are held against this with a 1" strip of steel as can be seen at the bottom of the left hand tube below.

I need to re-think my nozzle desgin though, as going up to a 3/8" feed pipe seems to have reduced the range. You're still gonna get very wet though.

Here are a couple of videos of me using the gun this weekend with my son and his friends (no sound as it's from CCTV).

Range Testing

2010-05-20T14:27:00.000-07:00

On Wednesday evening and with help from my son I did some range testing. As described in the previous post there were a few tweaks I could do.

First I de-burred the inner nozzle diameter and tested this with the system pressurised to 100psi.

Here is a not very scientific test shot.

I then applied an external taper to the nozzle:

As mentioned in the previous post, the idea is to minimise air turbulence as the water leaves the nozzle.

I fully charged the system with water (I still need to find it's capacity in litres) and pressurised to 100psi.

Here is a video showing range and duration.

I still believe I can improve on this. The current nozzle tapers internally to 3mm then has a run of 15mm to the outside world. I plan to machine a second nozzle that exits at the taper end.

I also plan to upgrade the tube from the pressure vessel from 1/4" to 3/8" pipe...however, when I got home from work tonight I was surrounded by my son and friends who were armed to the teeth with water guns. Never mind the nozzle. This means war.

I've diverted my efforts to make a harness to allow it to be worn 'Ghostbusters' style. Watch this space.

Tweaking my nozzle

2010-05-18T14:40:00.002-07:00

The tapered reamer I ordered arrived:

This is a low quality hand reamer but was sufficiently sharp to cut a taper into the Delrin. This taper has a 3mm minimum diameter so I shortened the nozzle to minimise the run length of the final diameter, although the nozzle still has about a 1.5cm run of 3.5mm diameter.

Here the reamer has been laid alongside the nozzle with the end of the reamer at level with the end of the taper inside the nozzle.

I tested this today at 90psi and got 50 feet out of it with a 45 degree nozzle angle. This is a definite improvement to a nozzle with a constant internal diameter. However, I am still not happy with the way the stream is breaking up.

I'm going to try the following:

Examining the taper inside the nozzle showed that I had left a burr on the nozzle inlet and outlet orifices.These need to be removed.
Reduce the run length of the final 3.5mm internal diameter of the nozzle so that the end of the taper meets the end of the nozzle.
Taper the outside of the nozzle in case there is some air turbulence..
Put an internal chamfer on the outlet orifice.

All these are easy to implement and the weather is forecast to be warm this weekend....maybe I can use it in anger....?

Nozzle Time

2010-05-15T13:36:00.000-07:00

I got fed up of waiting for a tapered reamer I ordered from ebay to arrive and decided to make a start on the tapered nozzle without it.

I started with a 500mm long bar of 22mm diameter Delrin:

I then cut a 120mm length of this, and turned it on the lathe to allow me to cut 3/8" 19TPI BSP thread onto it.

Delrin machines beautifully. I'll be using it more from now on.

I had an unexpected problem when I can to use the 3/8" die I bought. The die holder I have is 1 1/4" but the die is 1 1/2". I looked through my stash of threading tools but I have nothing bigger.

I solved this by holding the die in the lathe chuck and turning the chuck with the chuck key. I was able to hold the Delrin rod by hand to keep it straight as the thread was cut.

I then applied a chamfer to make it easier to start the thread.

Here is the proto-nozzle with 3/8" thread.

The tapered reamer I have ordered has a minimum diameter of 3mm so I drilled a 3mm hole through the nozzle.

Here is the partially finished nozzle attached to the 3/8" ball valve.

And alongside:

Arrival

2010-05-13T14:45:00.000-07:00

I tried the 1.5mm nozzle at 90psi and it was, as I expected, a complete failure. It didn't manage to project more than 10ft...but:

The new lathe tools, 3/8" BSP die and 20mm Delrin rod arrived today. If the tapered reamer comes I'll be able to make a tapered nozzle this weekend.

New Nozzle

2010-05-11T13:51:00.000-07:00

I filled a standard nozzle with epoxy resin and drilled it out to have a 1.5mm diameter hole. I was hoping that might increase the range but the more I read about hydrodynamics the more I believe it will actually reduce it.

This is because the narrower diameter will resist the flow of water through the nozzle. I'm going to try it as soon as possible.

Super Soaker Central recommend a tapered design for maximum effect but these are not readily available so I've decided to make one.

I've order some 22mm diameter Delrin bar which is easy to machine and I intend to use a tapered reamer to obtain a conical internal diameter.

Testing

2010-05-09T14:33:00.000-07:00

I completed the assembly today and managed to get a few tests in.

The first thing I had to do was fit the Schrader valve. These seem to be very difficult to source in the UK unless they are already attached to a tyre. In the end I found a guy on ebay selling these:

They are intended for Mini Metro shock absorbers but they are ideal for me for three reasons:

They have a standard, wide thread (M12 x 1.75) making it easy to source a tap and as the thread diameter is wide, it should give a secure mount.
It is made of brass and so won't rust.
Cost: Only £3.89

The PVC pipe that I am using has a wall width of about 4mm. I was concerned that mounting the above in a tapped hole might result in the PVC becoming distorted, or the valve becoming insecure. To fix this I decided to mount the valve at the union of the 90 degree elbow joint pipe as the elbow joints have a wall thickness of about 6mm.

Because I am paranoid, I also decided to fit an additional PVC shim from an offcut of pipe to give a total wall thickness of 4 + 6 + 4mm = 14mm.

I made the shim by using a hole cutter to cut a 35mm disc from an offcut of pipe.

However, this pipe is of a daimeter designed to fit inside the elbow but needs to sit on the outside of the elbow. This means that the outer diameter is greater than the diameter of the pipe this disc was cut from. To allow this to sit flush on the elbow I 'baked' the disc in the oven at gas mark 6 for 15 minutes to make the PVC malleable. I then pressed it over the elbow until it cooled and hardened. Here is the shim in place on the elbow.

I then solvent welded the disc to the elbow, drilled it out to 10mm then tapped it. I also filed it flat to allow the Schrader valve to fit flush.

Here is the complete assembly:

It was now time to pressure test the system. I fired up the compressor and pressurised to 30psi. There were no leaks. Now it was time to fit the water outlet port.

I decided to use a pneumatic quick fit connector for the outlet as it does not stick out very far and allows quick (dis)connection of the pipe:

This is one of the connectors I had left over from Halloween and has an 8mm pipe diameter.

I used the same 'shim and cook' method to fit this at the very bottom of the tank. My Grandad left me a varied selection of imperial taps, one of which was 1/4" BSP which is the correct thread for this fitting.

I knocked up a basic trigger using a few pneumatic bits and pieces I got from work when they shut down our electronic assembly department. I got the ball valve from ebay.

Here is a close up of the nozzle and ball valve:

Here is a picture of Josh testing it for me at 80 psi.

I was disappointed by the range. Anyone on the receiving end will get drenched as it dumped 3 litres in about 25 seconds. The stream breaks up much earlier than I was expecting. Examining the bore of the nozzle I noticed it was very rough so I drilled it out to 4mm on my lathe.

This had no effect. I then changed to nozzles of 6mm and 3mm. Neither showed any improvement on range. I upped the pressure to 90 psi and got a maximum range of 32 feet. I think that I need to reduce the nozzle diameter or that there is too much resistance in the pipe from the tank to the nozzle. I've filled a nozzle with epoxy and will drill it out when it's dry.

Range could also be increased by upping the pressure. The PVC tube is rated for a maximum of 131 psi, but I feel a bit nervous about taking it so close to its rated limit.

Riotous Assembly

2010-05-07T15:19:00.000-07:00

The screw thread end set I got to serve as the water inlet has a different diameter than the 1" pressure pipe I bought to connect it to the main tank:

To get around this I turned a section of 1" pipe down to fit the end set:

Here it is connected to the watwer inlet 'T' piece:

I glued the entire system together today. I'm going to leave it for 24 hours before pressure testing.

Sticky Situation

2010-05-06T14:27:00.000-07:00

I started using the solvent weld to join the pipe sections together. The solvent weld system comes in two parts: A cleaner and the actual solvent weld. These are the most volatile chemicals I heave ever used. I had to ventiliate my work area three times during this operation.

The speed which the solvent sets at is scary. About 3 seconds. When I ordered I did not realise I was going to get 'very fast cure'. This is an understatement . I only just managed to align the parts in time, and there is no going back once it has set.

Checking the design

2010-05-03T14:00:00.000-07:00

Today I tried out the design without glue. You can see the small end set threaded cap in the second picture. This has an internal diameter of 1" so which should allow for pretty rapid refilling. I'm checking my stash of threaded pipe fittings for some appropriate means of attaching a pipe to the bottom of the tank.

New Project.....at last!

2010-05-02T14:03:00.000-07:00

Halloween has been and gone and although we are nearly half way through 2010 I've decided to start a new project.

My 7 year old son, Josh loves a water fight. So we've decided to make the water gun from hell.
After some research I found this design which I thought would meet my usual criteria of fun and danger.

The design calls for high pressure PVC piping which is incredibly expensive in the UK for some reason. The only people who sell it at a low cost per metre insist upon you buying a crate of 5m lengths.

In the end I got my supplies from koi fish suppliers here. This pipe is rated PN9 which is good for 131PSI in old money.

Here is a picture of the parts I ordered:

The T piece and the 4" to 2" and 2" to 1" reducers next to it are to allow me to connect the screw cap end set (at the top left hand side) via the 1" pipe at the bottom. This screw cap is to be the inlet to top up the water. This differs somewhat from the linked design but as the availability of parts are is limited here, a compromise was the only solution.

I have a feeling I will be requiring some custom fittings for this project, so I dusted off my lathe. It has not been run for 10 years but it's still in running order. It comes complete with thread cutting gears, but only if I want to produce Whitworth threads.

The final part of this project is to be a solenoid valve to control flow. The original design uses a ball valve but this is both cumbersome and slow to respond. I intend to use a small MPU to control a 12V solenoid. If this responds fast enough, I should be able to have several modes selectable with a push button:

Single shot.
3 shots rapid.
Full auto.
Continuous.

This all depends upon the performance of the solenoid I've ordered. They don't publish the operational frequency. I'll just have to give it a go.

Here's a pic of the one I ordered:

Post Halloween Video

2009-11-07T14:42:00.000-08:00

Halloween has come and gone. Very favourable response to the show but only two videos worth watching. I've had real problems with the audio on these. I had to record the audio on a camcorder separate from the video recorder and had real problems synchronising the audio and video.
It turned out that the video was running at 60Hz and the audio at 50Hz so I had to use Audacity to change the audio lenghth by -20%.

Here are what I call 'screaming runners'

2009-10-25T15:35:00.000-07:00

After last weeks dry run I realised that the 300W stage flood I got from Ebay was too directional. I decided to go back the 150W halogen floodlight I used last year:

The problem with last year was that I sandwiched a green lighting gel inbetween the lamp housing and the class cover. Although lighting gel is rated for high temperature operation the gel I used ended up like this:

The bit in the middle was blackened and really attenuated the light output of the lamp.
Hoping that this was caused by thermal conduction from the glass plate, I made a steel
gel mount to mount the gel in front of the lamp with a 10mm air gap between the glass and the gel:

It's a pair of steel plates that bolt together, sandwiching the gel between them. It then mounts
on top of the floodlight:

I ran it for 3 hours without any obvious degredation to the gel.

Dry Run

2009-10-18T12:34:00.000-07:00

On Saturday night I managed to set the complete system up and do a dry run. I resurrected last years grave stones and set everything up more or less as detailed in the last posts diagram.

I videoed two system operations. One with lights off, which is how I intend to operate the system on the day. This does not show up very well on the camera though.

Another issue is that the strobe light does not show up on the video very well. It looks fine in the real world though.

The second run was with the 150W floodlight at mounted on my garage turned on. This shows up much better on the video but does not appear quite as spooky.

Here's what I've learned from the execercise:

I'm not sure about the 300W floodlight I'm using. I feel it is too directional. I think I'll try a 150W halogen flood.
I need to change the coffin lid opening sample, you can hardly hear it. nophead suggested that I record the squeaky door in trap 2 of the gents toilets at our workplace. So not feeling at all a bit pervy I started recording stuff in there with my phone, and just for the record, I was alone.
I think the PIR may need to be closer to the door.

Roll on Halloween.

Dry run planning

2009-10-16T15:55:00.001-07:00

Tomorrow I plan to do a dry run.

Here is a plan of everything as it will be laid out on the day:

My drive, and my neighbours run parallel, he's told me he won't be in on the night of halloween so his drive will be clear. I will also make sure my drive is clear to enhance the spookiness.

I've also drawn a plan of the electro-pneumatic system to give me a rough idea of what I need to wire up:

The two wierd symbols inbetween the pistons and the solenoid valves are the one way restrictors that allow the skeleton/lid to reset under gravity without excessive speed.

The flow restrictors allow me to control the acceleration of each piston.

The control software is complete. The only thing that needs to be done is time the up/down times of the lid/skeleton so I can ensure the software waits for sufficient time before transitioning to a new state (e.g. CoffinLidOpen).

I also need to make sure that the audio sample I have for the coffin lid rising lasts long enough for the lid to rise. I plan to use the excellent 'Audacity' to stretch/shrink the sample time without affecting the pitch.

Making progress.

2009-10-14T14:29:00.001-07:00

I've been working on a distribution board for the coffin. It takes the output from the PC driver board and feeds it to the coffin LEDs and solenoid valves.

It's no item of beauty but it works:

The hardware is now complete. I'm hoping to do a dry run this weekend.

Illuminating

2009-10-04T14:31:00.000-07:00

I have made some led strips to provide an eerie green illumination within the coffin as the lid opens. They are strips of 9mm plywood with five 10000mcd 10mm LEDs attached. I've split them into two parts to allow them to be fitted along the edges of the coffin.

Here is a picture of the LEDs illuminated:

And a close up:

The LEDs will be illuminated as the lid starts to open, and turned off when it has closed.

Changes

2009-10-04T14:25:00.000-07:00

It's been pointed out that there is an uneccessary transition to the reset skeleton state from the coffin lid open state in the statechart below (thanks Richard). I've re-drawn it and added another state to play a 'creaking door' sample as the coffin lid opens.

The state which opens the lid without playing a sample is used when the lid opens from the doorbell button. At this time the thunder sample is playing and the creak sample would be inaudible.

Here is the new statechart:

Coffin time

2009-10-01T14:36:00.000-07:00

I've been working on a design for the software to drive the coffin. I've decided that it
is potentially too scary for smaller kids, so I've designed the coffin to work in three modes:

Green: No lid opening or skeleton rising
Amber: PIR detector cause lid to rise. No skeleton.
Red: PIR causes lid to rise, skeleton rises if doorbell pressed.

With this system I can dynamically control the show as required (I'm going to remote desktop into the controller PC from a laptop). I've added a 'demo mode' override that will enable the full show from any mode. At any stage the system can be reset with a physical reset switch.

Here is a StarUML state chart of the coffin state machine:

Assembling the real thing

2009-09-26T13:51:00.001-07:00

Today I started to put the rest of the wood together to form the coffin plinth. I fitted the skeleton raising hardware and realised that the force required to lift the skeleton was warping the back panel of the plinth so I added some reinforcing struts.

Here's a pic of the plinth with the lifter bar raised.

And a close up of the lifter bar mounting. The two pieces of wood next to the lifter bar screw into the sheet of wood that covers the innards of the plinth. The helps to further reduce the torsion on the back panel of the plinth.

I also fitted the coffin lid and the lid lifting mechanism. Here the skeleton lifting bar is in the down position with 'Albert' attached.

Here's a video of it working:

Busy week

2009-09-26T13:42:00.000-07:00

I've been busy. I've spent the last few evenings assembling the electronics that will enable me to control all the pneumatics from a PC. I've made two mistakes on the board design:

1) The linear regulator holes were too small. It was a simple job to drill them out to the right size but this removes the through hole plating, the result of which is that I've had to solder the pins top and bottom.

2) I got the pad spacing of the 25 way D type connector I was going to connect to the PC with completely wrong. So wrong that the conenctor I wanted to use will not fit in the holes. Fortuanately I had some 25 way cable lying around (as one does) and I've soldered this cable directly to the board and put a connector on the other end to plug into the pc.

Here's a pic:

Coffin time

2009-09-20T14:50:00.000-07:00

Got some 9mm plywood yesterday and started on building 'the coffin'

Fast boat from China

2009-09-17T13:33:00.000-07:00

The printed circuit boards I had made arrived today. They are good quality and four turned up when I only paid for one! Not bad considering I only placed the order on the 4th Sept. and they have been made in and shipped from China!

This sometimes happens when they have a big space on the PCB blanks that they use. It is cheaper for them to fill as much space as possible and so if they have a small design (like mine) that can fill the gaps with they will use it repeatedly.

Good news for me as the boards work out at £11.50 each. Can't argue with that.
Trouble is though, I seem to have got the silk screen over the pads on one of the surface mount footprints. Ah well.

Now where's that soldering iron?