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Maker Pro

Low power cutoff not working

gregfox

Mar 25, 2013
162
Joined
Mar 25, 2013
Messages
162
I must add re the above, I can get the load to come on, by adjusting VR1, but if I set it, say, to go off at 3.5V, it will not go back on at any, up to 4.2V or down to 3.0V. It just stays off, and if I set it to go ON at any voltage(3-4.2v) it will only dim as it get down to 3.0V, and not turn off. I thought the TLV431 would act like a Schmitt trigger, but in this case..no.
 

crutschow

May 7, 2021
517
Joined
May 7, 2021
Messages
517
Here are all the readings,
Your REF voltage is way off.
It should be 1.24V at the trip point.
The pot setting should be adjusted until you get that voltage where you want the circuit to change states.
 

gregfox

Mar 25, 2013
162
Joined
Mar 25, 2013
Messages
162
Yes I set it to 1.25V and the load would go off, but would not turn back on. I don't know what else to do, I'm about to give up on this circuit and try using a LM339,
but thank you for the help, and time.
 

gregfox

Mar 25, 2013
162
Joined
Mar 25, 2013
Messages
162
I was suspicious when on the bread board I would get different readings at different times. When I soldered in onto a perf boars it worked 100% as it should have. The problem was that the 1/4 watt resistors I was using were too small for the breadboard, that is the wire leads were very thin and didn't make good contact in the breadboard. I got the resistors from Amazon and I think the lead size is thinner then it should be. I hope others don't fall into this trap.
Thanks again for the help!
 
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