Did you look at REFf with a scope? Is that an oscillator? On Tue, Dec 4, 2018 at 3:44 PM <[email protected]> wrote:
> They also have a pair of LEDs in parallel with each other but in series > with the op amp power rail to indicate output. Crazy all over the place. > > *From:* Mark Radabaugh > *Sent:* Tuesday, December 4, 2018 2:29 PM > *To:* AnimalFarm Microwave Users Group > *Subject:* Re: [AFMUG] OT Linear Circuit > > Check the V- side of the circuit - is it tied to 0v or is that the > output? > > https://www.edn.com/design/analog/4320338/Op-amp-can-source-or-sink-current > > version (e) looks a bit like what you have and they are using the negative > rail of the chip as a constant current source. > > Mark > > On Dec 4, 2018, at 3:51 PM, [email protected] wrote: > > Nope. The sensor is a different part of the circuit. > > *From:* Mark Radabaugh > *Sent:* Tuesday, December 4, 2018 1:41 PM > *To:* AnimalFarm Microwave Users Group > *Subject:* Re: [AFMUG] OT Linear Circuit > > Seems like one of those resistors is the sensor? To me it looks like the > output is going to try to stay just over 3V but will lag ‘ref out’ up or > down if there is any voltage on it. I can’t recall if op amps can sink > current or not. > > The wife was annoyed that the contractor blew up the new fan hood for the > kitchen remodel with a dead short on the output. A Replacement board was 8 > weeks out. “Can’t you get out your special catalog and fix it?”. I > suppose - hum.. this circuit board is built to drive more than one fan. > Let’s take this SCR out and move it over here, solder a new fuse in here… > yep - don’t even need to order parts. > > Mark > > > On Dec 4, 2018, at 2:43 PM, <[email protected]> <[email protected]> wrote: > > I am reverse engineering a temp control circuit on an electric tankless > hot water heater. > Manufacturer says no user replicable parts inside. Oh yeah? > > It has this as a reference voltage circuit (below) for a comparator to > compare against a thermistor and pot combo. > LM324 > > Odd taking a reference voltage from an input. Have never seen this > circuit before. I think I have drawn it correctly. > The op amp will drive the output to minimize the differences between pins > 5&6 so pin 6 should reflect the voltage of the divider with lower > impedance. > > Anyone see why this wouldn’t work? I was sure I had traced it > incorrectly, but I think this really is the circuit. > It seems the values of R10 and R11 are not critical. Or are they? > > > <image[1].png> > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > > ------------------------------ > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > > > > ------------------------------ > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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