•  
  •  

Power supply failure alarm

Most of the power supply failure indicator circuits need a separate power supply for themselves. But the alarm circuit presented here needs no additional supply source. It employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit which sounds an alarm for a reasonable duration when the supply fails.
This circuit can be used as an alarm for power supplies in the range of 5V to 15V.
To calibrate the circuit, first connect the power supply (5 to 15V) then vary the potentiometer VR1 until the buzzer goes from on to off.

Whenever the supply fails, resistor R2 pulls the base of transistor low and saturates it, turning the buzzer ON.

If there are any problems please contact webmaster@electronic-circuits-diagrams.com

Please share & like

NTE 501-0010 KU1031S28 10k ohm RV4AYsd103A Potentiometer
$17.49 NTE 501-0010 KU1031S28 10k ohm RV4AYsd103A Potentiometer picture
Vintage General Radio Type 214 Rheostat or Potentiometer - 20 Ohms
$15.0 Vintage General Radio Type 214 Rheostat or Potentiometer - 20 Ohms picture
271-1605 Radio Shack Assorted Potentiometers and Trimmers Pk of 12
$3.49 271-1605 Radio Shack Assorted Potentiometers and Trimmers Pk of 12 picture
5 Potentiometers Assorted 7.5K Ohms, Ohmite & Others, Lot 29, Made in USA
$14.99 5 Potentiometers Assorted 7.5K Ohms, Ohmite & Others,  Lot 29, Made in USA picture
1 Feedback Potentiometer, 5K Ohm SPECTROL # 130-5K, Lot 27 Orig.Box, Made in USA
$14.99 1 Feedback Potentiometer, 5K Ohm SPECTROL # 130-5K, Lot 27 Orig.Box, Made in USA picture