Control, Motor Controls
SOLAR POWERED PUMP MOTOR CONTROLLER
A Discover Circuits visitor
had a problem. He needed a simple on/off controller for his solar powered water
pump. His system used two 12v 50 watt solar panels wired in series. The
power from the solar panels drove a submerged water pump. However, during
overcast skies the pump motor did not operate properly due to the lack of power from
the panel. He wanted a circuit which would turn off power to the motor during
low sun conditions. The circuit below performs this function. A small 0.1”
x 0.1” photodiode monitors the sunlight intensity. The current from the diode is
proportional to sunlight intensity. An adjustable load resistor across the diode
converts the current into a voltage and feeds the to a voltage comparator circuit.
The output of the comparator drives a small n-channel MOSFET, which in turn drives a
high current p-channel MOSFET, controlling power to the pump motor. When the
sunlight is less than one fourth of full intensity, power to the motor is turned off.