Hi - I'm trying to do something similar - 16f877 pic turning on/off a
triac that switches a bit of an unusual AC waveform - AC, but not a sine
wave, 4Khz / 120V approximately.  Very low power - a few milliamps at most.

I haven't used triacs before and I'm getting nothing but grief.  I have
a bag (100 of) MAC228A8 - motorola "sensitive gate" triacs, but what is
happening is that the triac switches on when the gate is positive or
negative - its only off when the gate is floating.

Do you use some kind of zero-crossover detect as part of your circuit ?
I'd rather not build such, I really only need on/off right now.

I will be building many of these, as in 24 triac switches on one board
with the PIC, and keeping the component count to a minimum for both cost
and space savings is desirable...

Any help most gratefully appreciated.
Jesse


Anand Dhuru wrote:
> Hi folks,
>
> I have built a circuit around a 16F628 that drives a Triac directly (PIC - 220 ohms - gate) and it works fine with incandescent lamps / bulbs. Since I am not interested in controlling the phase angle as such (the load is to be on, or off, the intensity is not to be controlled) I am not pulsing the gate of the triac; the pin driving the gate is always either on, or off.
>
> Now, my question is, can this setup be used to switch heavier loads such as an air-conditioner, if I use a triac of an appropriate rating?
>
> Which brings me to the second question! Even triacs rated at 12 Amps, 400 volts come in a TO220 package. Can these devices really control the load of an air-conditioner without blowing up? Would a heat sink be required?
>
> Incidentally, I have 230 volts AC in my country, and the AC I'm interested in controlling would be 1.5 tons.
>
> Any advice here would be greatly appreciated, folks!
>
> Thanks and regards,
>
> Anand Dhuru
>
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