AC Lights Flashing and Blink Control Circuit Using 555 Timer and TRIAC

Robert Auger's picture

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Joined: Nov 03, 2020

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AC Lights Flashing and Blink Control Circuit Using 555 Timer and TRIAC
November 14, 2020 - 11:23pm

This is a very interresting circuit and I've been looking for something like that for a while. Got all the components, followed the shcematic and built the breadboard for testing. 

Unfortunately, it does not work. I can get the LED to blink at various rate using the variable resistance but the AC circuit refuses to work. I use 5vdc as input to the 555 timer (output is 2.9vdc into the optocoupler). since I am in Canada, it's 120VAC instead of 220 but I dont think it makes a difference. Also, I am using a LED house bulb instead of incandescent. Tried both to no avail. The TRIAC is a bt136 and tested OK. 

Any ideas.... 
Thanks for the help and insights

Robert

Debashis Das's picture

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Joined: Dec 02, 2019

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Hi Robert, In the circuit diagram there is an LED D1, first check that part of the circuit is working or not. if it's not working then the problem is within 555 timer circuit section, please check that section first.

Robert Auger's picture

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Good morning and thanks for the quick reply. 

The 555 part of the circuit works very well and the LED flashes properly when turning the variable resistor. However, I can't get the AC bulb to flash...

Debashis Das's picture

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so the problem must be in the TRIAC and its driving section, please try the circuit given in the below link(Just use the TRIAC section).

circuitdigest.com/fullimage?i=circuitdiagram_mic/AC-Fan-Regulator-Control-Circuit.png

Robert Auger's picture

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Thanks for the suggestions. The circuit I am using is a project from this site (as the title suggest) and here is the cirduit diagram :

As stated, it works well up to the LED. After that , nothing. I followed everything to exact specs and can't get the light bulb to blink.

AC Bulb Blinking Circuit Diagram

Sourav Gupta's picture

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Change the R4 value to 1k and short the R6.

Robert Auger's picture

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Thanks for the advice, will try it tonight and report back

Robert Auger's picture

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I had to put this on hold for a while but thanks to all your kind help, the thing is up an running well.

R4 and R6 is 10K 1/2 watt. The rest is as per schematic. Any other resistance (1k and shorting R6) would blow up.

Olivia Williams's picture

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Joined: Feb 27, 2020

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It is a simple circuit which consists of a 555 Timer IC to generate PWM pulse, this pulse is then used to control the blinking interval of the AC bulb through a TRIAC circuit which drives the AC bulb.