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Off timer with alarm

We published various timer based project but now we are going to publish a different type of timer based project. Here, is a simple inexpensive and attain grabbing circuit “Off Timer with Alarm”. This circuit automatic turns off the electrical appliance when set time is complete with alarm.

Circuit description of off timer with alarm

The entire circuit circuit of off timer with alarm is build and fabricated around transistor. Transistor T1 and T2 is used to drive the relay and transistor T3 and T4 is used to drive the piezobuzzer. The glowing LED LED1 indicate relay RL1 is energized where glowing LED LED2 with buzzer sound indicates relay RL1 is de-energized. The time period of this timer circuit is set by adjusting VR1 and switch SW1 starts time of timer circuit.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R1, R5, R7 = 1 KΩ

R2 = 100 KΩ

R3 = 10 KΩ

R4, R6 = 22 KΩ

VR­1 = 1 MΩ

Capacitors

C1 = 2200 µF/25V

C2 = 100 µF/25V

Semiconductors

T1, T3, T4 = BC547

T2 = SL100

D1 = 1N4001

D2, D3 = 1N4148

Miscellaneous

LED1 = Green

LED2 = RED

RL1 = 12V, 200Ω 1C/O relay

PZ1 = Piezo Buzzer

SW1 = Push-to-on Switch

 

 

Related Project

  1. Appliance Timer An appliance can be turned on at a desired time for a specific time interval
  2. CMOS Pocketable TimeKeeper Main purpose of this circuit is to avoid getting late
  3. Programmable Timer for Appliance This project can switch on and switch off the appliance in selected preset time
  4. The Universal Timer offer an ultra wide range of time period having pin point precision
  5. Timer With Musical Alarm musical song is heard after time period is over.

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