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OK, so I posted this on O U dot com so I'll go ahead and post it here too:
@Spokane1:
That's nice work! I know how tedious that kind of thing is, especially when working from photographs that may not be too clear or from good angles.
But.... It seems from your schematics that the entire bit of circuitry that includes the components associated with U4, U2 and U1 is a Red Herring that does not connect to the rest of the circuit at all, other than being powered by the Vcc supply. This is the case in both the Experimental and the Presentation schematics. I'm sure you noticed this when you were drawing them up. This simplifies the problem greatly.
So here's what I think it's doing, based on your schematics. We appear to have the 556 timer (U3) providing a clock signal that goes unchanged to both the H-Bridge and the Synchronous Diode. And we also have in the Presentation circuit, two monostable multivibrators U5 and U7. U7 appears to be an oscillator that provides pulses to the U8 hex inverter, which go through two of U8's gates then fed to the H-bridge. But this same signal through only one gate of the U8 is then fed back to the other monostable multivibrator U5 to trigger it, I believe, and it provides a pulse that goes to the Synchronous Diode. The U8 hex inverter also passes the input signal from U7 through three gates which then goes to the H-bridge. So the hex inverter's two outputs to the H-bridge are cleaned up, squared-off and oppositely phased versions of the pulse signal from U7. The U6 is not used in the Presentation circuit. There doesn't appear to be anything that synchronizes the U3 556 clock with the U7-U5 clock system. The U3 clock is fixed frequency and pulse width but the U7 and U5 multivibrators have trimpots for adjustments of either pulse width or frequency or both.
In the Experimental version, the U7 oscillator isn't used and an external FG (or two) is presumed to provide the clock signal for the U8 hex inverter and also the feedback signal for triggering the U5 monostable multivibrator.
Did you notice that my "mockup" of the U4 circuit (the TS372 dual comparator) oscillates, when it oscillates, at exactly 60 Hz? This is undoubtedly due to those essentially floating reference pins 2 and 5, making the thing so sensitive and unstable that it picks up EMI from the house wiring, power supplies, etc. and oscillates in step with it, when the voltage supplied to the 1k resistor is just right. That is, if I built it right to begin with and if my TL082 is behaving as the TS372 would. Of course this issue is moot because this section of the circuitry isn't actually connected to anything in both the Experimental and the Presentation schematics.
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It would be great if someone else with TTL experience could correct, add to or subtract from my guesstimation. Unfortunately I don't have any 74HC123 chips in my stash but at least I can try to breadboard the 556 clock portion later on today FWIW.
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Topic: Graham Gunderson Energy conference High COP demonstration (Read 235659 times)
