Hi
I am using a self designed home automation system(5 loads + 1 fan) where the fan speed is being controlled in five different steps(0 - off,1,2,3,4,5 - full)by zero cross detection & triac firing control method.So far,the circuit is running fine over a year.
But
Today,i bought my Micsig differential probe(DP10013) & thought to attach it across the Fan to see the chopped waveform.So I did & found that the chopped waveform is being distorted.
The main principle of the circuit is when a zero cross is detected,the MCU will delay some time(for say,5ms for speed 1 , 3.5ms for speed - 4 etc) & turn on the triac by a simple H-L pulse of 100uS.The Triac will turn off automatically during the next zero cross.For speed 5(full speed),the MOC3021 as well as the triac will always stay on.
After the Triac turned on(No problem here),when the waveform gradually reaches zero,then a heavy spike is occuring.I am using BTB16-600BW snubberless Triac with MOC3021 Optocoupler with snubber.
My question is Why this is happening & is it somehow going to create problem in the future either for the Fan or the circuit or is it normal?
I am attaching the circuit & different waveforms,Please take a look.
Another thing I would like to ask that should I replace the MOC3021 with snubberless FOD420?Will that create any difference?
I am using a self designed home automation system(5 loads + 1 fan) where the fan speed is being controlled in five different steps(0 - off,1,2,3,4,5 - full)by zero cross detection & triac firing control method.So far,the circuit is running fine over a year.
But
Today,i bought my Micsig differential probe(DP10013) & thought to attach it across the Fan to see the chopped waveform.So I did & found that the chopped waveform is being distorted.
The main principle of the circuit is when a zero cross is detected,the MCU will delay some time(for say,5ms for speed 1 , 3.5ms for speed - 4 etc) & turn on the triac by a simple H-L pulse of 100uS.The Triac will turn off automatically during the next zero cross.For speed 5(full speed),the MOC3021 as well as the triac will always stay on.
After the Triac turned on(No problem here),when the waveform gradually reaches zero,then a heavy spike is occuring.I am using BTB16-600BW snubberless Triac with MOC3021 Optocoupler with snubber.
My question is Why this is happening & is it somehow going to create problem in the future either for the Fan or the circuit or is it normal?
I am attaching the circuit & different waveforms,Please take a look.
Another thing I would like to ask that should I replace the MOC3021 with snubberless FOD420?Will that create any difference?
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