The Traffic Light Hack

Here's a basic outline of how the hack functions:

1. An application uses inpout32.dll to turn on a specific pin of the parallel port.
2. This current in turn causes the line driver chip to allow 5 VDC to flow through the SPDT relay.
3. The relay turns on and the light comes on.

There are three SPDT relays, one for each light. One problem I encountered when hacking this together was that the power coming out of the parallel port was not enough to throw a relay that could handle 125VAC. The parallel port itself was able to activate a Reed relay, but as soon as I hooked up the Reed relay to a light bulb, it almost immediately fried. Instead, the power had to be cascaded gradually, from the parallel port's power, to 5VDC from an AC adapter, and finally to the 125VAC.

Unfortunately, I don't know how to draw out a schematic for this hack, so I hope the pictures and explanations suffice. If you need any clarifications, please don't hesitate to leave a comment.

More information is provided in the picture captions. I'm no electrical engineer, so please leave comments if anything I've said is inaccurate, or if you have any questions or comments.