Thanks for the reply grumpy
I get the acid joke (chem 1A)...... I'm guessing 1ph would be a low ph and as such would be acidic.
I was trying to say a single phase induction motor with capacitors now controlling motor speed. This being different than a shaded pole version as I understand it.
I have a ceiling fan in my lab that I am working with. I have hard wired it to high (pull switch has been removed) common on caps pack to black hot.
this works fine and I am easily able to turn this on and off to high with basic zero crossing opto with triac and snubber.
So I am guessing I need to build a zero crossing detection circuit and use that to then to fire the triac after the desired delay. I have non-zero crossing triacs so I was thinking replace the zero crossing triac (my thinking is the two would be redundant and cause obvious problems) in my on off circuit with the non zero crossing one. and fire it according to the desired delay.
I have run across a project where they have recommended something to the effect of using timing (pwm) to fire on off what looks like 5 times per cycle (in a pulse train) see figure below last image. The first and fifth pwm would be effective and the other three would make no difference but I am having a bit of a time getting it in my head. It seems to me just programatically controlling the timing in milliseconds would be more efficient and not too difficult to do
1) The first waveform in the above figure shows a normal 50Hz AC phase signal consisting of a sinusoidal rising and falling 330V peak positive, and negative pulses, with respect to the central zero line. This central zero line is termed as the zero crossing line for the AC phase signals.
The triac can be expected to conduct the shown signal continuously if its gate DC trigger is continuous without breaks.
2) The second figure shows how a triac can be forced to conduct only during positive half cycles in response to its gate triggers (PWM shown in red) at every alternate positive zero crossings of the phase cycles.This results in a 50% phase control.
3) The third figure shows an identical response wherein the pulses are timed to produce alternately at every negative zero crossing of the AC phase, which also results in a 50% phase control for the triac and the load.
However producing such timed PWMs at different calculated zero crossing nodes can be difficult and complex, therefore an easy approach for acquiring any desired proportion of phase control is to employ timed pulse trains as shown in the 4rth figure above.
4) In this figure bursts of 4 PWMs can be seen after every alternate phase cycle which results in around 30% reduction in the triac operation and the same for the connected load.
Any opinions would be very appreciated