Automatic cut off power saver circuit

Common electrical appliances, especially night lamps and other lighting options are often left switched ON even when they are needed anymore. This results in unnecessary power wastage and also reduces the lifetime of the appliance. Hence, it becomes utmost important for a user to regulate the usage of each and every electrical appliance.

Fortunately, science provides us with several options to device out a gadget which can aid in regulation of working of these electrical gadgets. From preset timer circuit to light sensitive circuits, several projects can be attached to the devices to regulate their operations and save electricity.

Here is a possible solution to prevent the wastage of energy if you forget to switch off the bathroom or terrace lamp. Once it is switched on, it stays on for 22 minutes and then automatically turns off. The lamp will turn on only if the switch is turned off and turned on again.Save Energy. It is precious.

This circuit can drive CFL, Tube light and Incandescent lamps, Electric iron etc. It uses a latching timer circuit based on CD 4060. It is the 14 stage ripple free binary counter IC with 10 outputs. The timing cycle depends on the timing components C3 and R4 and with the given values, the output Q9 (Pin 15) turns high after 22 minutes to activate the relay. AC lamp is connected through the common and NC contacts of the relay so that when the AC switch is turned on, both the circuit and the lamp gets power. Red LED starts to blinkonce in 21 seconds indicating the lamp on. After 22 minutes, output Q9 turns high and triggers the relay driver T1. Relay turns on and cut off the power to the lamp. When Q9 becomes high, diode D5 forward biases and inhibits the clock input (Pin11) of IC1 and the oscillation stops. This latches the output Q9 till the power is switched off. Red LED then stops blinking and remains lit. White LED is provided in the circuit to locate the AC switch easily in darkness. It turns on when the lamp turns off.

Role of other components

C2- Resets IC1 at power on

R1- Keeps the reset pin 12 of IC1 in the ground potential to allow it to starts oscillation

C4 – Gives a short delay before T1 switches on/off. This prevents relay clicking if transients develop in power supply and provides a clean relay switching

D6 – Free wheel diode to remove back e.m.f when the relay turns off. This protects T1

Time setting

It is easy to set the relay on time by changing the value of either C3 or R4

Value of R4

1 M- 4 Mts

2.2 M- 10 Mts

4.7 M -22 Mts

10 M- 47 Mts

Another useful application

If you want to switch off the Porch light, Garden light or backyard light after 3 hours automatically modify the circuit as follows

1. Change the value of R4 to 10 M

2. Use output Q11 – Pin1 to connect T1. This output will go high after 3 hours 9 minutes.