There can be reasons for using a PIC for simple apps like this - if
the whole thing is line powered (i.e. no transformer), you need to
keep triac drive current down to reduce the size of the dropper cap,
so you want to use a narrow firing pulse. If your load is inductive,
you may need to issue several pulses to guarantee reliable firing due
to current phase shift, therefore an 'intelligent' PIC based solution
can sometimes be worthwhile even for apparently trival apps, and the
cost of a 'C508 is hardly going to break the bank!


On Thu, 13 Dec 2001 14:12:48 -0500, you wrote:

>The suggestion was to use a zero crossing opto; why do you need a PIC?
>
>> -----Original Message-----
>> From: electme [mailto:electme@IHUG.COM.AU]
>> Sent: Thursday, December 13, 2001 9:52 AM
>> To: PICLIST@MITVMA.MIT.EDU
>> Subject: Re: [EE]: controlling power supplies
>>
>>
>> how about a pic to sense zero crossing that switches a snubberless
>> triac.They have higher di/dt for surge current & no moving
>> parts , better
>> reliability
>> glen
>>
>> At 03:11 pm Monday 10/12/2001 -0500, you wrote:
>> >Just be sure to use a zero-cross firing opto, otherwise you
>> will still get
>> >random spikes on switching.
>> >
>> >Chris
>> > >
>> > > Ash,
>> > >
>> > > Inside of solid state relay is a triac with opto-coupler
>> on input with
>> > > Ziner diode thru a resister. Triacs are always better.
>> > > mechanical relay
>> > > Will generate spike RFI it is bad for sensitive electronics.
>> > >
>> > > Andre Abelian
>> > >
>> > >
>> >
>> >--
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>>
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