I built a pump control circuit using a 741 as a comparator, driving a TIP120 (Darlington transistor) to run the pump. (Those are the parts I've got)
I used a NTC thermistor to sense the water temp. (not waterproofed and tested in water yet, air only) I got some interesting quirks, and I think I got the bugs worked out, but I have some questions.
If the inverting input is floating, will the voltage follow the non-inverting input? (I think my pot was not connected fully)
After I got the first issue resolved, the pump would not fully shut off. Is this because the output of a 741 with a single supply never really goes to zero? It worked much better when I connected a 2.2k pulldown resistor to the base.
I'm hoping I got it right this time and didn't miss something. (Multisim didn't have a TIP120)
Thanks in advance.
I used a NTC thermistor to sense the water temp. (not waterproofed and tested in water yet, air only) I got some interesting quirks, and I think I got the bugs worked out, but I have some questions.
If the inverting input is floating, will the voltage follow the non-inverting input? (I think my pot was not connected fully)
After I got the first issue resolved, the pump would not fully shut off. Is this because the output of a 741 with a single supply never really goes to zero? It worked much better when I connected a 2.2k pulldown resistor to the base.
I'm hoping I got it right this time and didn't miss something. (Multisim didn't have a TIP120)
Thanks in advance.
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