Reservoir Pump Controller

This circuit operates an automotive windscreen washer pump to fill a 20-litre drum from a 205-litre water reservoir. The drum is suspended above a drip line, which irrigates a vegetable backyard. Two chrome steel probes established within the drum act as sensors for the device. One probe is positioned at the excessive water mark, the other at about half-full. The pump power is switched with the aid of a 12V automotive relay (RLY1). Two op amps (IC1a & IC1b) linked as voltage comparators form the basis of the circuit. 

Initially, assume a falling water stage with the pump switched off. When the water level exposes the decrease probe, the non-inverting input (pin 5) of IC1b rises to about 7.4V. With trimpot VR2 correctly adjusted, this can be higher than the voltage on pin 6. The output (pin 7) therefore swings excessive, biasing Q1 into habitsion. This in turn result ins Q4 to behavior, switching on the relay and starting the pump. 

In addition, when Q4 switches on it supplies base current to Q3 by manner of a 6.8kO resistor. Initially, this current wafts throughout the 47µF capacitor, but once its base-emitter voltage reaches about zero.6V, Q3 behaviors. This action latches Q4 in the \"on\" state, because its base present can go with the flow to floor by implys of Q3 when Q1 ceases behavioring – on the method in which to occur when the rising water stage reaches the low probe. When the water degree reaches the high probe, the voltage on the non-inverting enter (pin 2) of IC1a decreases markedly as a outcome of the habitsivity of the water.

Circuit diagram:

Reservoir Pump Controller Circuit Diagram

If trimpot VR1 is appropriately adjusted, the output (pin 1) swings excessive, switching on Q2. This discharges the 47µF capacitor and robs Q3 of its base present, switching this transistor off. This in flip switches off Q4 and the relay. The zener diodes and 1kO collection resistors at the probe enters protect the op amp’s high impedance inputs from the effects of static discharge. The 47µF capacitor in parallel with the base-emitter junction of Q1 prevents the latching operate from being activated when energy is utilized to the circuit. The author’s setup is energyed from an previous car battery charged from a 12V solar panel.

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