Time Delay Circuit: Build Your Appliance Protector

Description

Safeguard domestic equipment from voltage surges utilizing this straightforward delay circuit. Whenever electrical power to the devices is activated or resumes after a power outage, the oscillator begins functioning and D5 illuminates. This process continues for three minutes. Subsequently, the output of IC CD4060, specifically Q14, activates the gate of the SCR through D4, simultaneously resetting the counter. The cathode of the SCR is then energized, powering the relay coil to engage the appliance and D6 glows. Button SW1 enables a rapid start without requiring the delay period to elapse.

Circuit Diagram:

Parts:

Circuit Operation:

The core element of this circuit is IC CD4060, a versatile integrated circuit comprised of two inverter gates designed for clock generation and a 14-bit binary ripple counter. The clock oscillations within this circuit are controlled by resistor R1 and capacitor C1. Within IC CD4060, the inverter gates produce oscillating signals. Only two of the IC's outputs (Q5 and Q14) are utilized in this design. Q5 is connected to an LED (D5) for visual indication, while Q14 initiates the triggering of the SCR through D4, acting also as a counter reset. The anode of the SCR is connected to a +9V power source, and the cathode is connected to the relay coil. The other terminal of the relay coil is linked to the negative supply, and the relay’s contacts are used for switching the appliance into operation.