Solar Powered Differential Controller
For a small PV powered solar hotwater system with a small pump (20 watts or less) this solar powered differential controller is just what the doctor ordered with a price to match. From the illustration aboveyou can see where the PV panels or DC supply connects to the controller. The pump plugs right into J1 pin 1&2. The DC power is hooked to J1 pins 3&4 and the thermistor thermistor probes are connected to J2 pins 1,2&3 in the manner illustrated above.
There is a built in protection diode incase you make a mistake and reverse polarities.
There is a voltage regulator that limits current flow if the probes are shorted.
The PVC comes with two 10K NTC thermistor probes.
The differential adjustment allows the user to balance heat gain with power consumption.
The red LED brightness indicates the heat available for collection
The green LED indicates the status of the pump.
The solid state MOSFET relay allows the controller to remain stable at those low voltages when a pump is first activated. The MOSFET can handle a pump up to 20 watts. A battery backup is not needed with this controller.
The opamp is in a socket so it may be replaced easily if necessary, but should never need replacing
The PVC differential controller may be mounted on a wall with one screw.
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