Electronics > Beginners
Mosfet circuit with load indicator design question.
Zero999:
The LM393 won't work reliably when one of its inputs gets within 3V of the positive rail, so another potential divider on the MOSFET is a good idea.
The value of R1 is probably too low, as the maximum gate-source voltage rating of most MOSFETs is only 20V, which would be exceeded, with 24V and 100R and 10k for a potential divider.
exe:
--- Quote from: MarkF on April 12, 2019, 06:18:04 am ---Then I think a LM393 comparator is what you want instead of an op-amp.
You are looking for a switch not an amplifier.
--- End quote ---
I don't think this matters for this application. Why having extra stock of comparators if a cheap opamp does the job?
Zero999:
Yes, a single supply op-amp or comparator will do. It's a low speed design, so the LM358 is fine.
The simplest option is to connect the LED in parallel with the MOSFET, but the logic will be reversed.
MarkF:
--- Quote from: GarySmith on April 12, 2019, 06:14:53 am ---The idea is that if the load dies (as in the case of my hot end element dying for example) the indicator would still show active. Right now it's an LED but ideally I would like the indicator (LED or whatever) to be a 5v digital value that I pump to a raspberry PI
--- End quote ---
I believe the Raspberry PI GPIO logic is 3.3V and NOT 5V.
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