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Simple 220V Diac Controlled LED Flasher Circuit

This circuit maybe easy way to make LED blink using AC power.

Circuit is simple it make one or more LED flash using high voltage DC from mains.

We can use it as mains power indicator or just for flashing light effect.

Circuit Working:

Parts List:

ComponentQuantity
Resistors
22k 1/4 watt2
220Ω 1/4 watt2
Capacitor
Electrolytic 10µF 100V1
Semiconductors
Diode 1N40071
Diac DB31
LED 5mm 20mA1

This circuit use diac to switch LED ON and OFF again and again.

Diac mostly used in circuits to make pulse and trigger things like SCR and triac.

When voltage is low diac stay open with only tiny current pass.

But when voltage go high up to breakdown level diac start to conduct more current.

Usually it need around 35V DC to start working.

Different from SCR diac can work both sides means in both directions.

In this circuit DB3 diac is used which easy to find.

Diode D1 change AC into high voltage DC and resistor R1 slow down current so diac and LED does not get damaged.

Most of time LED stay OFF.

When the capacitor is fully charged voltage go high enough and diac turn ON and LED lights up.

Resistor R2 ensures LED does not get too much current and keep it safe around 30mA.

After LED flash a capacitor C1 start to discharge and voltage goes down by stopping the diac and LED turn OFF.

This charging and discharging again and again make the flashing.

How fast it flash depend on size of capacitor C1, big value means slower flash and small value means faster.

If voltage does not reach diac level with current R1 one can try 10k resistor but ensure it is 5 watt type.

Formula:

Below are some formulas we can use when checking how 220V Diac LED flasher circuit works.

Time Constant (τ):

This formula tell how long capacitor C1 take to charge and discharge.

It controls how fast LED blink.

Formula is:

τ = R × C

where:

Because all parts not always exact but real flash time can change a bit from what one calculates.

Few more things to remember:

Capacitor C1 should have voltage rating more than peak AC line voltage.

Resistor R2 keep LED safe by limiting how much current which goes through it.

When C1 voltage reach breakdown point diac DB3 act like a switch and let current go to LED.

Be careful! This circuit use high voltage which can prove to be very dangerous.

If not sure how to work with mains power better call licensed electrician to stay safe.

How to Build?

To build a Simple 220V Diac Controlled LED Flasher Circuit below mentioned are the assembling steps:

Safety First:

Component Placement:

Wiring:

Testing and Adjustment:

Safety Measures:

Note:

Conclusion:

This 220V Diac LED Flasher is simple circuit which uses easy to find parts to make LED blink using AC mains power.

If we build it carefully and follow all safety steps it can work as mains power indicator or just flashing light for fun or for other use.

References:

Datasheet Diac DB3

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