The 49th Parallel

The 49th Parallel is a simple data acquisition board with 32 digital inputs and four (trivially expandable to eight) 8-bit analog inputs. Like all good data acquisition boards, it was built for a party, to control canada.

In addition to the inputs, it has eight bits of digital outputs and one 8-bit analog output. The D/A part was kind of thrown together at the last minute, so it probably needs to be buffered with an op amp to do anything useful. (At the party, it controlled an analog meter.) See the DAC0802 datasheet for examples.

It's called the 49th Parallel because it provides the interface for Canada, and the 49th parallel is the border between the United States and (the country) Canada. Also, it interfaces using the parallel port, so it's a pun.

Here is a schematic: PDF PostScript gschem

The part at the bottom of the schematic that's not connected to anything else is the Gratuitous Triangle Wave Oscillator. It generates a triangle wave that goes between close to ground and +6 volts, to pulsate a light bulb. This is highly important. (Of course, since the output goes into the base of a common-emitter driver, it doesn't really matter what the voltage is, but let it be known that I carefully [although futilely] adjusted it to go from 0 to 6 volts, using a very expensive analog storage oscilloscope. Such is life.) A switch connects between pins 1 and 2 of the header that it connects to and varies the rate of pulsating.

At the party, the 49th Parallel featured a large array of switches, knobs, buttons, and whatnot designed to entertain people on drugs. There are pictures. (The last one is while the board was under construction.)

Right now, I don't remember how to interface with it, so you'll have to look at the Canada source to figure it out. I'll get around to documenting it sometime.