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This redesign improves reliability while reducing complexity and component count. One dual package op amp, two pots, a trim pot for tuning run time window, a 555, three FET’s, a 12v DPST relay and handful of passives. (The real build also contains a fuse and reverse polarity protection diode)
Change the resistance of the 500k pot in the lower left corner to simulate a light dependent resistor under varying light levels(green trace). Watch as the comparators include hysteresis for filtering false triggers, the 555 indicates reset. Adjust the pots to set trigger light level (blue trace) and motor run time(orange trace). Use the run time trim pot to set runtime sweep range.
This circuit works as advertised and has been feeding my chickens for two weeks without issue.
*NOTE*
changing the light level from low to high while the capacitor is still discharging will crash the sim. This is a simulation artifact, there is no issue in reality.
The relay is technically unnecessary as a single low side FET would do the job, however I had issues with driving it into ohmic, reducing the output current to the motor. The second issue was using the other pole of the relay, this allows the reset circuit to directly sense if the relay had actually cycled and not if the FET had only received a signal. I feel the added components are worth the feedback accuracy.
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