At 05:00 PM 4/12/02 -0400, you wrote:
>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.

Issues:

1)      Commutation time  (the triac doesn't have time to turn off
        completely)

2)      Holding current (if you are using pulse drive)- at only a few
         mA the triac may or may not stay on until the next pulse.

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...

Can you say a little more about the load you are using and the
AC waveform? Possibly some other kind of switching device might be more
appropriate (probably).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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