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### Topic: rectified AC phase control (Read 8255 times)previous topic - next topic

#### dgueorguiev

##### Nov 28, 2017, 06:49 am
I need to power a coil with  variable DC pulses of 150-200V which have to be wide 2ms in synchronous with   the picks  of standard wave of AC( 60 Hz 120V)which is the power for second coil . I have arduino uno genuino  and used two triacs in line with zero crossing reference ,use rectified AC from up transformer  ,but i have not susses with programing the arduino. May be have flows in the schematic too. I am mechanical engineer and have little knowledge in electronics. I really need help ! See attachment

#### TomGeorge

#1
##### Nov 28, 2017, 09:24 am
Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
We need to see your circuit, a picture is worth a thousand words.
Please include power supply and component labels.

Thanks.. Tom..
Everything runs on smoke, let the smoke out, it stops running....

#### DrDiettrich

#2
##### Nov 28, 2017, 10:24 am
DC cannot be controlled by triacs.

#### TomGeorge

#3
##### Nov 28, 2017, 10:34 am
Hi,

I think the OP is using rectified AC, so it is pulsed DC.
But I think the Traic controlling the AC primary.

A circuit diagram will help...

Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### dgueorguiev

#4
##### Dec 02, 2017, 08:26 amLast Edit: Dec 02, 2017, 04:30 pm by dgueorguiev Reason: schematic for clarity
I think I have to use only one triac , but to be able to open and close the gate of the triac at the pick of the AC sinusoida .LIke if t is 8.333 ms(half wave) t1=1/3 t  and t2=2/3 t .After I have the wave cut I can rectified and supply to my coil.

#### TomGeorge

#5
##### Dec 02, 2017, 08:30 amLast Edit: Dec 02, 2017, 08:31 am by TomGeorge
Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
We need to see your circuit, a picture is worth a thousand words.
Please include power supply and component labels.

https://playground.arduino.cc/Main/ACPhaseControl

Thanks.. Tom..
Everything runs on smoke, let the smoke out, it stops running....

#### wvmarle

#6
##### Dec 02, 2017, 08:50 am
In this case I'd be more interested in a sketch of the expected waveforms and timing required. That I can't really imagine from the description.

Pulsed DC you would at least in theory be able to switch with a triac but only if the zero is zero enough, so to say: stray capacitance and inductance in your circuit may cause a large enough current to flow when the DC is supposed to be zero, to keep the triac on. In case of AC, with the voltage crossing zero, it's guaranteed to switch off.

Probably a triac to switch the AC, and a MOSFET to switch the DC where the Arduino takes care of the whole sequence. A 2 ms pulse is no problem for it to produce, following a trigger from a zero crossing detection, possibly with a specific delay.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### dgueorguiev

#7
##### Dec 02, 2017, 04:35 pm
I add a picture of my schematic on previous posting. I hope it will help and i will attach here to.

#### wvmarle

#8
##### Dec 02, 2017, 05:08 pm
OP's image:

Unfortunately too low resolution to be properly readable.

Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### TomGeorge

#9
##### Dec 02, 2017, 06:05 pm
Hi,
Your picture is not high enough in resolution to read everything you have written.

https://playground.arduino.cc/Main/ACPhaseControl

Tom..
Everything runs on smoke, let the smoke out, it stops running....

#### dgueorguiev

#10
##### Dec 02, 2017, 08:33 pm
Yes i look at  (https://playground.arduino.cc/Main/ACPhaseControl). But it is not clear how they get zero-crossing  signal from ( H11AA1). And I need to have triac open 3ms after zero-cross and close at 5.33ms after same crossing zero, for the remaining 3ms of half wave triac has to be closed. I am lost !.

#### Wawa

#11
##### Dec 02, 2017, 08:47 pm
I need to have triac open 3ms after zero-cross and close at 5.33ms after same crossing zero...
Not sure what you're trying to do, but you can't switch a triac off after you have turned it on.
A triac only turns off in the next zero crossing.
Leo..

#### TomGeorge

#12
##### Dec 03, 2017, 01:28 am
But it is not clear how they get zero-crossing  signal from ( H11AA1).
The signal out of the H11 is a 5V square wave that changes state on each of the AC input crossing points.
Tom...
Everything runs on smoke, let the smoke out, it stops running....

#### wvmarle

#13
##### Dec 03, 2017, 06:18 am
As I understand you try to switch the DC side. In that case, if you replace the TRIAC with a MOSFET you can switch it on and off. A TRIAC switches itself off upon zero crossing, you can't switch it off any other way.

Need better image of that schematic to see what you're trying to do. Again an image of the expected waveform would be very helpful in this case.

Basically, with the MOSFET approach, what you need to do:

Code: [Select]
`ISR () { // linked to a CHANGE on the zero crossing signal.  zeroCrossed = micros(); // Record the microsecond time.  zeroDetected = true;}loop() {  if (micros() - zeroCrossed >= 5330) {    // switch off MOSFET  else if (micros() - zeroCrossed >= 3000 && zeroDetected) {    zeroDetected = false; // ensure this can run only once per detected interrupt.    // switch on MOSFET  }}`

If you have more to do in your loop() and you're likely to be a little late in timing, you could use a timer interrupt for this.

When a zero crossing is detected, set the timer at 3000 us, when it's triggered set a new timer at 2330 us later and switch on the MOSFET, the next time switch off the MOSFET and reset the timer. Use a bool flags to keep track of which stage you are.

Code: [Select]
`ISR () { // linked to a CHANGE on the zero crossing signal.  zeroCrossed = micros(); // Record the microsecond time.  zeroDetected = true;  set timer at 3000 us.}timerInterrupt() {  if (zeroDetected) {    set timer at 2330 us.    switch on the mosfet    zeroDetected = false;  else {    switch off the timer (no more timer interrupts until set again in the ISR())    switch off the mosfet  }}`
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### dgueorguiev

#14
##### Dec 03, 2017, 10:37 pm
Thank you very much for suggestion to use MOSFET , But I have no knowledge how to switch on the internal timer of the Arduino and I connect Zero-cross signal to pin 2 of Arduino, but what about pin 4 that is in CODE from(https://playground.arduino.cc/Main/ACPhaseControl).How this pin 4 is connected to the circuit? I have MOSFET IRF630 and IRF9z24N that I can try to use , but I have problems to suit the programing code to the schematic . and the problem is that i have about 50A current and most of the parts i use are not suitable and burn. Looks i have to give up and use less voltage and lower the  amps.

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