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TRIAC based on/off circuit showing flash problem with LED lamp

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getfast_kiran:
I had made a circuit to turn load on and off using a TRIAC.
It all worked fine until the load was resistive or inductive.

As soon as I connected a LED lamp to the circuit all problems started coming in to the circuit. When the TRIAC was off. The LED lamp started to flash every few seconds with each flash becoming
brighter than the one before it.

So when I read about it in eevblog forum. I found a post where Mr. SeanB had said
" LED lamp with a TRIAC can cause issues of flashing when off, as the slight leakage current through the snubber capacitors can be enough to charge the power supply in the lamp up to startup, which will make the lamp either flicker when off, or flash every few seconds."

But I could not find a solution to it being supplied in the post or across the forum that I could find.

So if you guys could help me with the same. I really appreciate it and thankful for your time.

Here is the modification I did from the schematic. I used the earth as the return for voltage resistor circuit for voltage sensing even though I knew the earth is such a bouncy return path.
Also I removed one of those 100nf capacitors in the 5V stability correction.

Also instead of the 360 ohm resistor and 470 setup changed it to the MOC 3021 datasheet recommended 180 ohm and 2.4k combo resistance along with the 0.1uf X rated capacitor.

Looking forward for you instructions to recitify the issue.

getfast_kiran:
Following is the circuit used for the opto coupler 3021

Seekonk:
re you talking about a  you build it LED or a commercial LED LAMP.  I use <19W E27 lamps as night lights sometimes by putting a .1uf or smaller in series with the lamp.  Depending on the electronics inside, I get a nice low power lamp, it flashes, or doesn't turn on at all. All in series triac circuits have leakage issues. A good size RC (100ohm .47uF) across the lamp may solve some issues.

BrianHG:
As a test, can you try the circuit without the snubber cap?
Without the opto & add a resistive load on the gate to ensure it's off...

getfast_kiran:

--- Quote from: BrianHG on February 28, 2017, 07:31:06 am ---As a test, can you try the circuit without the snubber cap?
Without the opto & add a resistive load on the gate to ensure it's off...

--- End quote ---


As you told I removed the Snubber capacitance from both the TRIAC and the optocoupler.  Now the LED is perfectly off for nearly 1 hour.

Should I do the second part with opto completely removed.

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