The request
“A 12 V thermostat: a 10k NTC thermistor in a divider feeds an op-amp comparator with a 100k hysteresis resistor. The output drives an NPN transistor that switches a relay, with a flyback diode across the coil.”
Then tryLabel the op-amp as an LM358Add an LED that lights when the relay is on
What is in this drawing
Read the decisions behind it.
01
Used a Wheatstone bridge arrangement with NTC and fixed resistors to create a temperature-dependent voltage.
02
Added hysteresis via positive feedback from op-amp output to non-inverting input to prevent relay chattering.
This circuit is suitable for basic on-off temperature control in incubators, heating pads, and environmental chambers.
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