The circuit is using two power modes, which are a solar panel and a 6V 4AH or 4.5AH sealed lead acid battery, therefore in the daytime when solar panel receives sun light it will charge the battery and power the circuit and in the night time the circuit will be powered by the battery.
The circuit is using two 555 timer ICs. The IC1 is working as an automatic battery charger and the IC two is working as an automatic water pump controller. After the circuit is completed it will require some adjustments for the first time. First set the trip point of the automatic battery charger circuit, with the trip point we can adjust on what voltage the circuit will stop the battery charging. For that purpose take a variable power supply and set its voltage to 7.5V. Then remove the 6V battery from the circuit and connect that variable power supply in the place of battery. Now slightly adjust the trip point until the LED goes ON, that's it.
You can use any type of variable power supply available with you; you can also use a LM317 variable power supply or any other variable/adjustable power supply shown in our power supply circuits section.
The probes connected with the IC2 should be placed inside the tank as shown. The upper level probe should be placed at the top of the tank or at the place where you want stop the water pump and the bottom level probes should be placed slight up from the level where you want to start the water pump.
The figure below shows a project of a solar water pump controller circuit. The circuit will automatically switch ON water pump when water level in the tank reached below from the bottom level probes, and automatically switch OFF the pump when the water level will reach at the upper level probe.
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