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Simple monitor turn on delay circuit

This is a simple monitor turn on delay circuit. It uses a contact of relay acts as a switch. When we enter an AC main to this circuit. The circuit will delay working. While It reduces a surge current protection with a fuse. Same as current will gradually flow into the first period.

Currently, we use the same computer. Most are connected to an outlet with a switch to turn off with the easier to use. But when we turn off the switch, plug it in short strokes will be. Surge current flows into. This may result in damage and lost a hard drive. Therefore require a delay for a while. It is time to turn on itself, which will help prevent hard disk the damage.

Simple monitor turn on delay circuit

Figure 1 The simple delay turn on the monitor circuit

This circuit can be used with 220-volt house power. by contact of the relay switch to acting.

When 220-volt power input to the circuit, the lower the voltage to 220 volts to 15 Volts, with R1, R2, C1 and C2 current limiting it to about 41 milliamps.

And C Partners diodes ZD1 limited pressure it to 15 volts and Direct Optical Fire through D1,. D2 and C3 to the party circuit.

There will be current through R3 to charge C4, which takes time to charge and when the C4 charge fully to make a current flowing into pin B of Q1.

The Q1 runs and drive currents to RY1 switch contacts touch. Each per 220-volt power to the monitor acts C4 delay.

If you want a long delay, it added the C4, but if you want to delay it a little to reduce the C4.

The Diode-D3 prevent reverse voltage from the coil of a relay. Which may be damaged to the circuit.

How to build this projects
This project is not used many components so can assemble on the universal PCB board as Figure 2 the wiring and various components to look out carefully for the polarity of the electrolytic capacitors, Diodes, Transistor, and relay are correct.

Figure 2 the components layout and wiring of this project.

The components List

Resistors +5%
R1_470Ω 1W
R2_150K 0.5W
R3_3.3K ¼W
C1_0.01uF 250V_Polyester
C2_0.33uF 250V_Polyester
C3, C4_470uF 16V_Electrolytic
D1-D3_1N4007_1000V 1A Diodes
ZD1_Zener diode 15V 1W
RY_Relay 12V see text
The universal PCB board.

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This Post Has 2 Comments

  1. hi
    I have just built this circuit and checked it many times but the circuit blows upon power on. Has these been any corrections to the circuit or changes? thanks

  2. Sure it will blows because his is short R1 470 ohms from phase 220v to neutral

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