Circuit control boxes - parallel
The following pictures of my circuit controllers were shot with a Kodak DC260 digital camera (thanks Dennis for the use of the camera - it is appreciated!) These two show that they are nothing more than a power strip - until you notice the connector on the side. Also note that I removed the switch and circuit breaker normally found in a power strip and added another two outlets for a total of eight. That's because a parallel port on a PC has 8 out-going data lines and I wanted to use all 8 in one unit.
Here's a close-up of the centronics 50-pin parallel connector on the side:
And now for the inside of the device.... The ribbon cable's connector inside the unit is directly above the connector it mates with in the lower portion of the picture:
Here is a close-up. On the right is the connector the ribbon cable plugs into. There are 8 of these little circuit boards - one for each outlet. Each pair of outlets has been electrically separated into individual outlets on the white side with the blacks (hot) staying connected together. Each circuit board is one-sided and has three parts: a triac, optoisolator, and a 100ohm resistor. The tab of the triac is also the output, that's why the thick copper wire soldered to each tab goes directly into the outlet. The small "speaker wire" comes from the ribbon cable connector - there is a wire for each circuit board which runs to each optoisolator. All of the ground wires from the opto's are connected together and run back to the signal ground pin from the connector.
As one can see, it is crowded but it works very well. All one has to do on the computer is put the selected output pin on the parallel port (LPTx:) high and the respective outlet turns on. Make it go low and the outlet turns off. It is an added bonus that the computer automatically latches these pins.
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Last modified on 02/01/01