Hello Techie,
I am working on LED dimmable light, I have basic electronic circuit of 4n25 optocoupler, MOC3021 non zero crossing based optoisolator & Triac. I am using Arduino UNO as a controller which control the intensity(Dimmable) of light.
When the program is uploaded the light is flickering? I am not getting that why it is flickering as I am getting proper zero crossing detector on my DSO. For reference I am attaching the circuit diagram and my code. kindly help me for getting the solution for this issue.
Apparently a common problem - I recently learned about it on youtube, I think it was either bigclivedotcom or electroboom channel, been watching those a bit too much over the past few days. It has to do with capacitive leakage currents, typically through a snubber circuit - power supply's bootstrap cap charges up, tries to start the lamp, quickly runs out of power, and that was the flicker.
One solution I recall is a large resistor in parallel to the light in question, preventing the build-up of charge.
There is a reason for the zero cross isolators. For AC dimming you delay both quardents from the zero cross. If you do not do that you will get flickering unless your clock is in exact sync with the AC line. Try this link for more information on dimming: AC Dimmer Circuit | DXARTS | University of Washington
Hi,
Mains LED lights in most cases use capacitive dropping to convert the mains to a level suitable for LEDs.
The capacitive dropper causes the current through the lamp and triac to lead the voltage waveform by 90deg.
A triac needs zero load current to turn OFF after it has been triggered ON.
If you have a resistive load, the current will be in phase with the voltage, so when the current became zero, the voltage across the load circuit was also zero and the dimmer will function properly.
With capacitive loads, when the current becomes zero, there is still a voltage across the load circuit which makes the turning OFF of the triac either impossible and it stays ON or it turns OFF erratically.
google AC led dimmer
There are links there as to why a normal dimmer will not work reliably with most LED mains lighting.
This link will explain it better and the solution;
Tom...
PS, You are probably using leading edge technique.
I have seen this idea before: that we can use the reactance of a capacitor to
reduce AC voltage to a lamp or LED. That may be true but, then there is no
current limiting as with using a resistor. So we have to watch out for
over current operation.
