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Mystery box

My roommate found this device in his basement.  It was apparently something a former roommate had built.  He doesn't know what it does.  When I flip the switch, the green LED comes on, but turning the dials don't seem to do anything in particular, at least that I can see.




One of the IC's is labeled MC14013BCP, which Google says is a "Dual D-Type Flip-Flop". Another is labeled LM324N, "Quad Operational Amplifier". The third is a 7555CN, a "CMOS Timer, Gen-Purpose".

Anyone know what this thing does?  I have enough skill in electronics to know what the parts are, but not enough to figure out what they do together.

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bluedeer
Dec. 31st, 2008 09:09 am (UTC)
I'm guessing either some kind of electronic metronome or a continuity tester of some kind. The pot suggests to me either a volume control for the Quad OP Amp, or a variable resistor to adjust timing.
harlequeen
Dec. 31st, 2008 09:10 am (UTC)
It could be a signal generator. Try attaching a scope...
harlequeen
Dec. 31st, 2008 10:01 am (UTC)
People at work agree, probably generating a square wave. Maybe a sine wave too, poorly filtered on that cap there.

Edited at 2008-12-31 10:02 am (UTC)
harlequeen
Dec. 31st, 2008 10:02 am (UTC)
I also assume that one pot controls freq., the other amp.
captpackrat
Jan. 1st, 2009 01:50 am (UTC)
I don't have a scope, but my multimeter has a frequency function. It measured from about 10 Hz to 2000 Hz as I turned the dials.
tiggerfox
Dec. 31st, 2008 09:41 am (UTC)
It is hard to say without closer examination of how the circuit is connected. The flip flop is basically a switch, the op-amp can be used as a sensor and the 555 is your clock. A time delay switch perhaps. The three banana jacks are interesting, you could swap them after a period of time. Or send a signal form the red pole to the left, then the right after time. It probably still works, and probably does something useful. Very interesting indeed, whoever made it put some care into constructing it in a nice enclosure.
captpackrat
Jan. 1st, 2009 01:53 am (UTC)
I'm actually rather surprised by the enclosure, considering most of the other electronics projects in the basement and garage are little more than conglomerations of parts and wires.
tiggerfox
Jan. 1st, 2009 07:36 pm (UTC)
If said roommate wasn't into making his own circuit cards, it would indicate that this was kit. The enclosure was probably part if the kit. The 555 is one of the most prolific ic's ever made. It still works so you could probably find a use for it, neat find =)
twigmouse
Dec. 31st, 2008 06:54 pm (UTC)
TENS unit!

Hehe, not really, no transformer for step up. Oh well ;-)
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