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Physical Computing Night Light Circuit March 22, 2010

Posted by Tom Frobish in Physical Computing.
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The first thing for Physical computing we had to do was create some kind of circuit, so I decided to kind of go a little farther. I created a night light circuit that has problems 😛 Basically the circuit is supposed to turn on automatically in the dark and turn off in the daytime but can be turned on by pressing the button. I’m not actually sure what’s going on at the moment. The LED never fully turns off and it and only gets brighter when you press the switch. I don’t know if this is a characteristic of the 74ls00 (Quad NAND Gate)chip or not but when I check it it’s putting out a constant 1.4-1.6 volts and when I press the switch it puts out 3v (I have a little 3v coin battery on it) I’m pretty sure the chip is supposed to send out zero voltage when putting out a Low Signal.

Since the 74ls00 chip can only supply like 24mv it’s not strong enough to supply the LED to the brightness and it could hurt the chip so I put on a transistor to basically create a gate that activates when the chip sends it a High signal and routes power directly from the battery instead of through the chip.

So attached are the different revisions of the schematic and some poor quality photos of the breadboard. I’ll update with a cleaner setup, I have to put the circuit back together.

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