At 08:40 AM 10/29/02 -0600, you wrote:

>Yes there is a PIC in this thing.  The whole problem with the relay is, if
>I don't turn off in less than one half  60HZ AC cycle, I get big noise
>pulses off the relay contacts which get into everything including my PIC
>power supply.  Eventually one of these pulses either resets the PIC or
>makes it do wierd things.
>
>Imagine the NO and NC contact of a relay.  When the relay is firing, an
>arc is drawn from the NC contact.  If there is 120V from the NO to the NC
>contact, as this arc ionizes the air in the gap, and some inductance
>somewhere, the arc continues as the contacts move across the gap and these
>contacts are momentarily shorted together!  Yes this really happens, and
>yes it happens every time a relay is fired.  Look it up in Aromat (NAIS)
>technical literature.  In my circuit, the relay is choosing between
>half-wave and full-wave power.  As long as I fire during the correct phase
>of the AC cycle, there is only a diode drop voltage across my relay
>contacts. If I fire the relay during the wrong half, it momentarily shorts
>the NO and NC contacts, generates a huge pulse of energy at 2.5megacycles
>and about 1500 watts, and this literally goes everywhere.

Oh, why don't you just advance the switching to the relay by a few ms so
that switching takes place at the right time? It only has to be
*repeatable*, correct?  You have more than +/-4msec to play with on a 60Hz
line.

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

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