World's simplest " Automatic water level controller with high/low voltage cut off "( Tested OK)
This circuit has only few cheap components and very easy to assemble. This circuit is a modified version of my previous post for water level controller.Circuit can perform 4 operations as below
1) automatic switch on water pump when water level comes low in overhead tank
2) automatic switch off the pump when tank get full
3) Low voltage cut off protection for pump to a set voltage, say below 160 V
4) High voltage cut off protection for pump to a set voltage ,say above 250V
click circuit to enlarge
These all operations can be performed with this simple circuit. BC 547 will be always in ON condition, till the water level comes down to lower level. switching ON the 547, keeps 187 off condition. when water level lowers, 547 loses its base voltage and get off, results in switching ON 187 and relay connected to 187.Pump will switch off only when water rises to touch the tank upper probes.
If the voltage become low, while pump ON condition,187 loses its base voltage through zener and relay get cut off.
If the voltage become high,zener connected to 547 deliver base voltage to 547 . This condition switch ON 547 and ground the base of 187,resuting relay cut off.
Adjust the presets for the required cut off voltages. Relay contact Ampere rating is given as" x" in circuit because you have to choose a relay with contact ampere according to the pump HP.Only 3 wires are needed to overhead tank
