The technical details for Halloween 2003

Note: This article assumes you've read my 2001 and 2002 technical details. I don't describe in detail here some of the hardware when it is already described there.

This year, like last year, I did not use any PCs in my setup. It was controlled entirely by microcontrollers (MCUs). I used a total of 6 MCUs this year: master, laser, spider, turning-head dude, and two for the skull.

One thing I learned this year is that Lenoxx CD players are not a very reliable. I have 4 portable CD players and two boomboxes made by Lenoxx. In mid-summer, I tried them all out. None of them worked reliably. The problem was that the buttons, particularly the FF button, does not consistently respond to being pressed. Some times it goes, some times it doesn't. When I tried the CD players again in late summer, they worked perfectly. I'm guessing temperature and/or humidity was affecting the buttons' responsiveness. In any case, it looks like they will be usable for my purposes after all, but I wouldn't recommend buying them.

Because of the problem with the CD players in mid-summer, I went looking for new ones. When I went shopping, Walmart was selling a CD player by Durabrand for $13, so I bought one. After opening it, I discovered that all the printed material had Lenoxx on it, so apparently, Durabrand is just another name for Lenoxx. The CD player worked well, though, so I gave it a shot. It worked well through Halloween. Now, to see if it works next summer...

For information about hacking a CD player, click here.

The laser

Last year, I implemented a serial protocol to communicate between the laser MCU and the master MCU. While that protocol did work, it gave me a lot of headaches getting it to work reliably. After thinking about it, I realized that all of the communication I really need can be handled using the standby and run indicator lines that the master is already using, plus one line for the laser to indicate that the beam has been broken. The matrix looks like:

standby run laser Description
off off off Laser MCU is in sleep mode.
on off off Laser is on.
on off on Laser beam has been broken; master has not acknowledged.
on on on Laser beam has been broken; master has acknowledged.
on on off Laser has acknowledged the master's acknowledgement.
off off on Master is going to sleep; laser hasn't acknowledged.

The other two possible states are invalid. The run indicator will never be on when the standby indicator is off.

Since I no longer had a way to communicate to the master MCU the fact that the laser has gotten out of alignment with the light sensor, I added a buzzer to the laser's board. When the laser MCU detects that no light is hitting the light sensor even though the laser is on, it rings the buzzer until someone presses the reset button on the laser board, at which time the laser goes into alignment mode.

Skull info

Back to the Halloween 2003 pictures
2004 technical details

Page last modified on 09/17/2003