At 09:44 PM 6/16/01 +0530, you wrote:
>I have an application wherein the PIC is to drive an AC load at 240 volts,
about 10A. For certain reasons, I cannot use a relay and have to use a
TRIAC instead. Instead of using a TRIAC with a high current capacity of the
required value, can I 'parallel' two or three of them safely, and expect
them to share the load current? I have tried this technique briefly, and
nothing blew, but how safe / reliable is it?

It isn't, not very. Devices like triacs tend to "hog" current when there is
a temperature
differential. You *could* do it, by mounting them all on a common heat sink
and
arranging some kind of ballast resistors, but why bother?

For a commercial application with a (real) 10A (resistive) load, I'd use an
inexpensive 25A triac, most likely, or even a 40A unit. Even then,
protection (fusing)
can be an issue. You can cheap out and just use the fuse to protect wiring and
assume the triac will go if there is a short. You generally need a *lot*
more margin
than on relay contacts for long-term reliable operation in a production
situation.
Keep them cool, and keep in mind that failure of the eutectic die bond
(leading to
overheating and failure "on") is one of the common failure modes, so thermal
cycling should be minimized.  You'll have 10W, give or take, to get rid of.

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
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads