Use a 4N35 optocoupler instead of the one you have.
Ok, just to help me increase my knowledge - what is the reasoning behind changing the optocoupler?Use a 4N35 optocoupler instead of the one you have.
Ideally you need to scope the zero crossing pulses and see what's happening, also the triac gate signal, but if you haven't got a scope then use well proven trigger circuits and zero crossing detection systems rather than design your own and failing.Ok, just to help me increase my knowledge - what is the reasoning behind changing the optocoupler?
By the way, I want to thank everyone for their contributions and willingness to help. I feel like I've got a lot of study to do!
Not too sure that this is such a great idea. Think what happens if you increase the capacitance - the pulse gets shorter and shorter and eventually disappears. Best place for a capacitor is across the INPUT of the bridge rectifier, although it will delay the trigger pointOne possible fix is a capacitor across terminals 1 and 2 of the opto-isolator, to keep any glitches from causing a problem.
That's a problem if the mains is not exactly 50Hz - the output gets asymmetrical and you end up with net DC.Or are you sending a trigger pulse every cycle of the line power?
Definitely worth a try.Some folks have stablized their controllers by adding an incendescent light bulb across the motor, to change the pure reactance into an impedance. That should be simple to try.
Yes, sorry it's a BTA41 600B. The specs say it is a 50ma trigger current and 1.2v on-state voltage. Not sure what that means as regarding it being snubberless or not.Do you mean a SGS-Thomson BTA41, or BTB41? I’ve not come across a BT41. If so, there will be a suffix which tells you the voltage and the triggering current, and whether or not it is (allegedly) ”snubberless”.
Does your software lock out the zero-cross detector after it has detected a zero? I mean, there won’t be another zero crossing that it needs to detect for at least 9ms, so why bother looking, it just gives it the opportunity to detect one that doesn’t exist.
When it misfires, what exactly happens? Does it do a whole extra half-cycle? Or does it mistrigger for longer than that?
Do you mean, like a standard wall light dimmer? If so, the current through the variable resistance is AC. Put the opto inside a bridge rectifier and it would work.Here is a concept that could avoid the problem, which is to use a resistance controlled triac firing circuit, and then use the opto isolator as a current controlled resistance. That would avoid the possibility of timing issues in the controller from having any effect on the drive. because it is a high inertia motor and because fast speed changes are not required, slowing the response would be another way to avoid the issue. Unless there is some performance requirement that I have missed.. And there are quite a few triac speed control circuits that use a variable resistor for the control.
A universal motor (the one specified) is the only one that can be successfully speed controlled by phase firing.Your probably using the wrong type of motor.
Constant on is much better than pulsing. If the pulse is too short the triac only remains on for the length of the pulse, because the current through the inductor has not reached the triac's holding current. Holding current is very temperature-dependent.Pulseing is a little better than constant on.
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