Custom Clips

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I've been designing a custom lasertag 'King Of The Hill' system for a customer, and decided to try mounting the PCB with 3D printed clips.
It's a pain to put holes for PCB mounts as extra real estate is required, plus all the associated washers, screws etc.
So I designed a 3D PCB mount, which relies upon friction clips to hold the PCB in place. Here, the green PCB is held in place by the angled clips:

And in the real world:

The PCB is held securely and can be fitted or removed with ease.

Mendel90 Heated Chamber

I've been very happy with my Mendel90, but attempting to print larger parts in ABS resulted in the inevitable warping of the part as the ABS cools. Nophead has done a load of work on this subject, and my original printer uses a chamber also. So I designed some corner brackets to allow me to make a chamber for the Mendel90 from 6mm MDF. As there are no spare temperature inputs on the Melzi controller, I bought a cheap PID temp. controller off ebay, and wired it into a hot air gun. My '90 is in the garage and needs much more heat than cooling:



Below are the results, keeping the chamber at 45C makes a major difference to the warping. The right hand side shows the same part printed without heating:

This is using ABS juice to glue the parts to the bed. I'm going to try a combination of kapton tape and ABS juice next.

Humble Pi

My  main reprap printer uses the same, none standard,  control electronics as some of nophead's earlier printers. It differs from the standard reprap gear in that the firmware is a slave to the PC. All the gcode decoding is done by the PC, and simple move, temperature, extrude commands are sent to the reprap electronics.



This is great in that if I want to change the Z height, or adjust the filament dimensions or temps. I simply edit a Python script.
Also, the PC communicates with the control electronics over ethernet, so the USB timing issues just don't occur.

To keep the embedded code simple a static IP address is used. Mine is set to 192.168.7.8 and it works great.

Now the arrival of my Mendel90 means that I have to make a USB connection to the Melzi controller every time I want to do a print. This is a pain as I don't have a PC near where the Mendel90 is.

I decided to try the Raspberry Pi print server. It's great. I simply TightVNC into the Pi, and run Pronterface from there.

So today, I started a large 6 hour print at 10am. Around four PM I think 'It's about time I got that Raspberry Pi running' so I plug everything in. As the Pi powers up, the main printer halts with about 1 layer to go and just sits there spewing plastic. WTF!

Of course, with inevitable fate I'd set the Pi to have the same static IP as the first printer and the bloody thing lost its comms. to the host software.
Bugger...

New Lathe

I've been trying to make a 0.3mm hot end for a friend who agreed to exchange one for a completed Melzi controller board for my Mendel90.
My lathe is really old, and had been used in WWII by my grandfather to make parts for the war effort. As a result, it's a bit worn, and not really up to this sort of thing.



So last week I decided to replace it with this:



It's a Myford M-Type from 1949. It is in great condition and although it has a shorter bed, it is a bigger lathe.

After almost breaking my back installing it, I successfully bored a 0.3mm hole for the extruder nozzle:



Here is the hot end complete:

Open source UMT code

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Got my Milestag UMT lasertag software working.
I will be advancing the features of the software, but currently it supports:

• Red,blue,green,yellow team id.
• Data clone from core board.
• Compatible with standard UMT audio samples.
• Ammo box, respawn box,and most referee commands.

The project is very modular, and could be converted to most lasertag applications. It is available under the z-lib license on github at: https://github.com/tonygoacher/UMT_Open_Source

Please contact me if you would like a customised version of the code, or a particular feature adding.

This is a Hi-Tech 'C' project, their is a 45 day evaluation of the compiler available at: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en542849

UMT Software almost finished

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My Milestag microMT lasertag is coming along nicely. The infra red signal needs to be modulated at 56KHz to match the TSOP4856 sensors that are used to detect hits. I'm using the inbuilt PIC16f684 PWM to generate this frequency.

First I did a simple test to simply check I'd got the frequency right:



Not bad for a first attempt. I've already written the Milestag protocol transmit routine, but I tested the timings by simply turning a port output high or low as described here.
I replaced the port on off code with PWM on off code and got exactly what I wanted. Timed IR pulses modulated at 56KHz.



When I tested my shot packet against another lasertag unit, the second unit picked up the shot packet and seemed to interpret the shot power consistently, but with an incorrect shot power value. I need to look into this next.

Sparkfun serial LED display bracket

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The Milestag UMT lasertag system uses Sparkfun serial LED displays to show health, rounds etc. They are nice units but difficult to mount so I have designed a bracket to allow them to be neatly fitted and protected:



This has an integral 2mm acrylic sheet to protect the display, and a 2mm flange allows some leeway when making the cut out for it.

A small bracket is screwed in place at the back to hold the display in place, this also has a cut out to provide access to the display terminals:


It is available at the Tagbits shop here.