Different triac turn-on types


Thread Starter

Peter Butler

I now have a circuit diagram but no hardware.

When I finally get hardware I will control a MOC3021 triac which then controls a BTA08 triac for driving an AC fan motor. Does this combination force motor on only at the zero crossing? Or will power be presented to the motor as soon at I raise the control line on the MOC3021? (I’ve been told that triacs only turn off at the zero crossing so that part is not an issue.)

I may be able to request different part(s) if I act soon enough.

By moving a few lines of code my software can use either parts that turn on at the zero crossing or turn on immediately. But I have to know which I am using. I would rather have the motor power turn on at the zero crossing. This should minimize electrical noise. (Noise is a serious issue because fan power switching is near to a 160 to 300x voltage gain needed to convert thermocouple output into a 0-5V analog to digital converter.)

And while I am here what is/are the other triac part number(s) with the same power ratings that turn on the other way?