Windmeadow Labs

I ordered the Minipov kit from adafruit. POV stands for persistence of vision. Basically flashing seperate images fast enough to make them look like motion.

The kit uses 8 red leds. It is pretty simple to build, it only took about 45 minutes to solder together. It took a little more time than that to install all of the software onto my linux box.

Getting the minipov to display a readable image took some work though. Waving the thing as fast as I could would sort of make a readable image. I slowed the blink rate down some and that helped.

I finally got the hardware watchdog working on my Soekris Net4511. The Soekris box runs my webcam and X10 stuff. I installed Voyage linux on the box. The default sc520_wdt does not work with the watchdog on the Net45* boxes. I found a patch to apply. I didn't write the patch, I found it from a post by Jakub Schmidtke.

Update: It turns out Punky does have this patch in the default build of Voyage linux. I just happened to download a snapshot of voyage that didn't include the patch. Anyway if you want watchdog support on a net4511 give voyage a try. It is a pretty good distro.

A lot can happen. Thats why we need to high speed photography so we don't miss this action.

Shannon and I built a sound trigger from hiviz.com . When it hears a loud sound, it triggers a switch, which fires a camera flash. (works almost like the clapper).

Using this we were able to do some high speed photography and get pictures of balloons bursting.

You can see the pictures here.

I have been playing around with interfacing relays and stuff with a serial port. The kids and I did a fun project of building a squirrel trap. I thought I would cool to combine them together.

A Soekris single board computer is the brains. This is a little low power 486 computer. A laser pointer is used to detect when something is inside the trap. A small electric motor is used to pull the pins that hold open the doors.

A circuit is connected to the serial port that detects the beam. When the beam is broken the computer detects it. A relay is connected to the serial port. When the computer turns on the relay, a small electric motor runs and pulls the pins that hold the doors open. The doors shut and close the trap. The computer then takes a picture with a webcam and sends me a page.

Ever wanted to make your own laser beam security system. You know the kind they have in the movies, with dozens of lasers and the thief has to limbo through them.

Well, I just made a simple laser beam break detector. My computer can now tell when the beam is broken. The parts I used are:

1. 5.6k resistor
2. photo diode, Digikey part #PDB-V107-ND
3. serial port from my PC

You set the RTS pin of the serial port high. You then use the CTS pin to track the state of the photodiode. When the beam hits the diode, current from RTS will flow into CTS and the CTS pin will show high. When the beam is broken, the diode stops the current flow and the CTS pin goes low. Below is the circuit:

For a while I have wanted to control things with a serial port. It was pretty easy to control a relay with a serial port. With a standard serial port you can control 2 relays. (with a parallel port you can control 8 relays, but I don't have a parallel port on my system).

A standard PC serial port has 9 pins. Pin 4 - DTR (data terminal ready) and Pin 7 - RTS (request to send) can be used to control a relay. These two ports don't actually send data. They are used to signal the other device to tell it when to send data.

These pins can be set high or low. When set high, they each go to about +9 volts. When set low they go to about -9 volts. This voltage swing is what is used to run the the relay.

My latest project has been transmitting audio/sound over a cheap laser pointer. I found the original plans for this here.

The parts I used are:
1. Laser pointer level from Target
2. Cadmium-Sulfide Photocells (Radio Shack part 276-1657)
3. Audio output transformer (Radio Shack part 273-1380)
4. battery holder for 1 AA battery
5. battery holder for 3 AA batteries
6. Audio source ( I used the line out of my laptop)
7. Headphones
8. small piece of a dowel rod.

I picked the Target laser pointer level because it was the easiest to hack. First take the dowel rod and put a small nail in one end. Attach a wire to the nail. Put the dowel rod into the tube that holds the battery, then use a rubber band to hold it in place. Second attach a wire to the base of the laser pointer.

You can pick up the Rand McNally Streetfinder GPS for the Palm V for about $40 on Ebay. Problem is, if you don't have a Palm V, they aren't much good to you. I picked mine up at a garage sale for $10. After a little hacking I was able to get it to talk serial to my laptop. There is also a Streetfinder GPS for the Palm III. My guess is that this would work for it also, but since a don't have one I can't test out that theory.

To get the GPS to talk to a laptop you need to make a serial cable. You will need to connect to 4 of the pins on the GPS unit. Here is the pinout