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 <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
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