problem in BT136 and MOC3021

[embpic]

i have many problems by using relay for switching higher AC voltage.So, after googling some i came across TRIAC and optocoupler.
i read the previous thread regarding this but no final result circuit is given for reference.
but i have some doubts that how to detect the zero cross detector of AC voltage of 230Vac.that is for firing angle to ON the TRIAC.
i have to use PWM for this.
i am using P89V51RD2 and keil complier.

 

[FvM]

In most cases, an opto triac with zero crossing detector like MOC3041 and a triac can be considered as relay replacement. No reason to think about zero crossing detection on your side.

I don't see how "PWM" would come into view when replacing a relay.

 

[embpic]

Yes I have think replace relay and I also have to do dimmer for the output.

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This is my second output

 

[FvM]

So you want to perform phase angle control, that's a topic beyond relay replacement.

There are many previous threads about triac phase angle control and µC dimmers. Also application notes from Microchip and other controller vendors.

 

[embpic]

yes sir i know this is beyond relay replacement and for switch ON triac i have to give continue high pulse and for OFF low pulse.
but sir my problem is i don't know how to detect zero crossing for light dimmer application and i don't have exact circuit for that .
i am really confuse that which circuit to choose for dimmer application.

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After reading some articles on internet i get to know that MOC3021 have inbuilt zero crossing detector. so Is it right?

 

[bigdogguru]

You might want to have a look at the following thread:

https://www.edaboard.com/threads/219109/

It is a fairly in depth discussion concerning optocouplers and TRIACs, although the discussion is gear towards the use of the PIC microcontroller, most of the techniques can be ported to other microcontrollers.


BigDog

 

[embpic]

yes sir got the clear picture means for detecting zero crossing signal i have to implement like follows

i found this one in microchip's application note AN521.

and when detect the zero cross of AC line the start PWM timer and then just adjust the only duty cycle. is it correct?
and for MOC3021 and BT136 i have implemented following circuit as


Here AC voltage is 230 Vac.
is this procedure is correct?

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is this procedure is safe or dangerous?

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@bigdogguru
i have read the whole thread and got some idea but i was thinking about small circuit for dimmer to replace potentiometer . is there any isolated but small circuit for detecting zero cross.

 

[embpic]

hello if use p89v51rd2 and crystal of 12 mhz then i can not use to dimmer application. bcoz in pwm timer is only 8-bit and can give maximum delay of 0.25ms a=by using count as 6 in register.
so how can i achieve delay of 10 ms for dimmer application (PWM).

 

[FvM]

Consider any kind of software timers.

 

[embpic]

software timers means without interrupt ??

 

[FvM]

software timers means without interrupt ??

Not necessarily. Counting timer interrupts sounds like a promising idea.

 

[dwcookiemonster]

If you're looking for zero-cross detector, you can try this :



make your own modification for desired proper signal.

 

[AKENAFAB]

I made this and works great.
**it was for 127v not for 220v
**broken link removed**

regards!

 

[embpic]

thank you FvM i will try using timer

and thank you AKENAFAB and dwcookiemonster.

 

[embpic]

is this circuit workable and safe? and in india 230 Vac voltage for AC.then which kinda changes will required?

 

[AKENAFAB]

is this circuit workable and safe? and in india 230 Vac voltage for AC.then which kinda changes will required?

My circuit has been working for a while.

Just change resistor values for zerocross LED,triac resistors/moc3020(400v peak ) There are calculated for 127VAC.



regards!