helo all,

i am trying to make a dimmer circuit for FAN(inductive load)..i have googled a lot in this.
so if any one having idea of any cost effective dimmer ic which have inbuilt optocoupler which is used for triggering triac(which conducts current at zero crossing)..as well the protection circuit for voltage surges against triac from ac load...

if no ic is there ,then if the circuit am i intending to make for dimmer circuit using optocoupler and triac(with some protection element) suitable for ac inductive loads??the dimmer ckt i am making is for home automation system??1 more ques is if the relays (driven by micro)can be used to control the dimmer circuit or the dimmer circuit is controlled by microcontroller itself??

any help from ur side would be highly appreciated.
thanks in advance

 

Presumably this is a mains voltage fan? Depending on the type of fan motor (induction, shaded-pole, universal ...) a phase-control 'dimmer' circuit may not work. Many fan-motors have multiple windings instead for speed control.

 

Google "optocoupler diac dimmer".

 

so if any one having idea of any cost effective dimmer ic which have inbuilt optocoupler which is used for triggering triac(which conducts current at zero crossing)..as well the protection circuit for voltage surges against triac from ac load...

I believe you mean zero cross detection, not zero cross switching?
If you were to switch on at zero the Triac would stay on for the whole time and switch off at the next zero crossing after turn off.
Take a look at Fairchild AN-3006 for ideas.
Max.

 

True, if op wants phase control, can't switch on at zero.

And it's the nature of thyristors to switch off at near zero.

So what is the purpose of optocoupler?

What are you looking for that is different from a dimmer circuit?

With that knowledge someone will give a specific answer.

 

Presumably this is a mains voltage fan? Depending on the type of fan motor (induction, shaded-pole, universal ...) a phase-control 'dimmer' circuit may not work. Many fan-motors have multiple windings instead for speed control.

but sir many application notes and google says for dimming action on fan or controlling the speed of the fan we need to use phase controll circuit..
for this m using random phase optocoupler MOC3023 whose outputs will trigger triac (With some snubber circuit for protection against inductive load)..which in turn lowers or fastens the speed of the fan...
i hope u are getting what i am trying to do.please correct me if i am wrong at some point

 

I believe you mean zero cross detection, not zero cross switching?
If you were to switch on at zero the Triac would stay on for the whole time and switch off at the next zero crossing after turn off.
Take a look at Fairchild AN-3006 for ideas.
Max.

thanx sir for suggestion..i red it ...got to know i need to use random phase optocoupler for making a dimmer.

 

True, if op wants phase control, can't switch on at zero.

And it's the nature of thyristors to switch off at near zero.

So what is the purpose of optocoupler?

What are you looking for that is different from a dimmer circuit?

With that knowledge someone will give a specific answer.

optocoupler is used for isolation purposes so that in case there is some voltage hike or some overcurrent passing from the load(operating on 240v ac supply) or any kind of mishap it will not damage our microcontroller..

ya sir m looking for a dimmer circuit only..m using optocoupler from output of the micro ..the opto moc3023 output is used to trigger the triac(bt136)..suggest me with more ideas if any.

 

I don't know of an ic with both things that you need.

An isolated triac driver would be the moc3021 family.

Any optic isolator, connected to ac, like a 4n25 will work for a phase detector to time the trigger points .

 

http://forum.allaboutcircuits.com/attachment.php?attachmentid=62955&d=1388222188

 

http://forum.allaboutcircuits.com/attachment.php?attachmentid=62955&d=1388222188

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Sorry, it works for me. I don't know how to fix it.

Was worried about posting the pictures, but it's from AAC.