Any need for external zero cross detector.

[sjjm]

I am building a pic based heat controller which switches at the zero crossing points of the a.c mains. I have an mc3041 triac driver with an inbuilt zero cross detector, so is it neccessary for me to use a seperate external zero crossing detector.

 

[IanP]

MOC3041/2/ .. is a zero-crossing device .. you don't need to duplicte it's function ..

Regards,
IanP

 

[deperkin]

this does have a zero-crossing internal to the chip...
i have a question however...

If you use this optocoupler to say drive a small fan motor (AC single phase),
how does this zero-crossing come into play?

how could i go about using this optocoupler to control fan speed? any pointers would help.

 

[FvM]

ZCD opto-triacs don't work with inductive load. They may even feed a DC voltage (halfwave) and damage the motor.

ZCD opto-triacs can't be used for phase angle control.

 

[deperkin]

Thanks,
well noted.
I am currently using a Solid-State relay on the side... would this be better, or would you advise just getting a better opto?

 

[guti]

you can control the speed of the motor giving to the load a certain amount of cicles.

This way, if you activate the MOC 50 out of 100 cycles you're giving to the load a 50% of power. The only problem you have with this method is the inertia of your load...