Overvoltage and undervoltage monitor schematic circuit

Using this electronic schematic circuit we can monitor the voltage of some power supplies or the voltage of other circuits .

This circuit is very simple an required few components . The monitored voltage for this  undervoltage and overvoltage monitor circuit is maked using two Zenner diodes  . If the value of the monitored voltage goes below or above the value of the zenner diodes the LED will light .

The transistors used in this voltage monitor ( undervoltage and over voltage ) circuit is MPS3704,MPS3705 , 2N3704 , 2N3705 type or equivalents .

Monitored voltage must be connected on the circuit between the + an -  contacts .