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Simple Time Delay Circuit for DC Power

This Simple Time Delay Circuit for DC Power uses an SCR.

It is a really useful circuit that can be used in lots of different ways.

The way it works is quite easy to understand.

Sometimes, you need to wait a little bit before turning on a device or circuit.

This Simple Time Delay Circuit for DC Power gives you a delayed output after a set amount of time once you turn on the power.

It is great for cases where you want to turn on devices one after another or to prevent sudden spikes in current.

Input DC supply can be maximum 24V.

Circuit Working:

Parts List:

ComponentValue/TypeQuantity
Resistors100k 1/4 watt2
CapacitorsTantalum 1µF 35V1
Tantalum 10µF 35V1
SemiconductorsSCR 4A TIC106D1
Diode 1N40052
Zener Diode rating should be half the input supply voltage.1

The working of this circuit diagram is quite simple.

This circuit uses a special part called an SCR (Silicon Controlled Rectifier), which works like a switch to control when the output happens.

When you first turn on the power the capacitor C2 starts to fill up with energy through R2.

The amount of energy in C2 decides when the SCR will turn on.

At the beginning the SCR is turned OFF so no power goes to the output.

As C2 fills up it gets to a point where a little bit of current can flow through D3 and R2 which makes the SCR turn on.

Once the SCR is on, it lets power flow to the output.

Capacitor C1 and resistor R1 help keep everything steady and stop any accidental triggers.

D1 and D2 make sure the circuit works properly by stopping any unwanted current from flowing.

Formulas with Calculations:

The delay time T is determined mainly by the capacitor C2 and resistor R2.

It follows the charging equation:

T = R2 × C2 × ln(Vth / (Vcc – Vth))

where,

For example:

Assuming a 12V supply:

T = 100k × 10uF × ln(0.7 / (12 – 0.7))

T = 100k × 10uF × ln(0.7 / 11.3)

T = 100k × 10uF × (-2.33)

T = 2.33 seconds

This means the output will be delayed by about 2.33 seconds after applying power.

How to Build:

To build a Simple Time Delay Circuit for DC Power following steps are required to be followed:

Conclusion:

This Simple Time Delay Circuit for DC Power is helpful in various situations where devices need to turn on one after the other.

You can change the delay time by adjusting the values of the resistor and capacitor.

The SCR provides a steady switching system, which makes the circuit dependable and effective.

References:

A simple delay ON circuit

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