Sunday, 25 October 2009

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.

Sunday, 18 October 2009

Dry Run

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:
  1. 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.
  2. 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.
  3. I think the PIR may need to be closer to the door.

Roll on Halloween.

Friday, 16 October 2009

Dry run planning

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.

Wednesday, 14 October 2009

Making progress.

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.

Sunday, 4 October 2009


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.


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:

Thursday, 1 October 2009

Coffin time

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: