Sudden fluctuation in supply is a very big problem in industries and domestic applications. It causes a major loss for industries, offices and homes. This project gives a low cost and powerful solution for this problem. This Circuit protects refrigerators ,ACs, Microwave ovens as well as other appliances from over and under voltage fluctuations.

1. Presentation on
Over-/under-voltage
protection of electrical
appliance
Submitted by:
rakesh roshan(0701209329)
nishant kumar(0701209350)
abhishek pattnaik(0701209404)
narayan singh(0701209288)
ashish kumar nayak(0701209345)
Under guidance of Er. Alice Pradhan

2. Introduction:
 Sudden fluctuation in supply is a very big problem in
industries and domestic applications. It causes a
major loss for industries, offices and homes.
 This project gives a low cost and powerful solution for
this problem. This Circuit protects refrigerators ,ACs,
Microwave ovens as well as other appliances from
over and under voltage fluctuations.

3. Block diagram:

4. Circuit diagram

5. Simulated circuit diagram

6. Components:
 TRANSFORMER
 IC 7812
 LM 324 (OPERATIONAL AMPLIFIER)
 RELAY
 ZENER DIODE
 npn TRANSISTOR
 RESISTORS ,CAPACITORS AND DIODES

7. TRANSFORMER
 Step down transformer 230V/12V
 Operating frequency is 50HZ.
 Voltage is converted from 230v to 12v.
 Current rating is 1A.

8. IC LM7812
(VOLTAGE REGULATOR)
 Output current in excess of 1A.
 Output Voltages of 12V.
 current Internal thermal overload protection.
 No external components required.
 Output transistor safe area protection.
 Internal short circuit limit.

9. IC LM324
(OPERATIONAL AMPLIFIER)
Features :
 Large DC voltage gain:100 dB
 Wide power supply range:
 Single supply:3VDC to 32 VDC
 Dual supplies:±1.5VDC to ±16VDC
 Differential input voltage range equal to the power supply voltage
 Power drain suitable for battery operation
 Large output voltage swing:0VDC to VCC-1.5VDC

10. PIN CONFIGURATION (LM 324)

11.  Its rating is 12v, 200 ohm ,1 c/o relay.
Relay
•SPDT – Single Pole Double Throw.
A common terminal connects to either of two others.
Including two for the coil, such a relay has five terminals in
total.
A relay is an electrically operated switch.

12.  A Zener diode is a type of diode that permits current not only
in the forward direction like a normal diode, but also in the
reverse direction if the voltage is larger than the breakdown
voltage known as "Zener knee voltage" or "Zener voltage“.
 Zener diode of rating 6.0 v and 6.8 v are used in the circuit.
ZENER DIODE

13. BC 547 transistor is used in the circuit.
Transistor is used to energise the relay
when op-amp goes high.
npn TRANSISTOR

14. Diodes
Resistor
capacitor
RESISTORS,CAPACITORSAND DIODES

15. APPLICATIONS:
 Industrial machinery
 House hold items like TV, refrigerator, AC
 Agriculture Motors
 Water pumps

16. ADVANTAGES:
 Highly sensitive
 Fit and Forget system
 Low cost and reliable circuit
 Complete elimination of manpower
 Can handle heavy loads up to 7A
 Auto switch OFF in abnormal conditions
 Auto switch ON in safe conditions

17. CONCLUSION:
It is helpful in protecting electrical appliances in very
effective way.

18. REFERENCE:
1) www.wikipedia.org
2) www.efy.com
3) www.google.com

19. THANKs..