> I've googled myself silly with RC snubbers, MOVs and so on. My
> application is not life-safety, but it has the potential for
> economic (and emotional) loss - it's to control a breeding box. I
> need to maintain a fairly well defined environment in terms of UV
> lighting and temperature.
>
> Anything I can do to improve the reliability and longevity of the
> relays is a plus. Since the relays on the TS-RELAY look sealed and
> non-socketed, I have no way to check for sparks and no way to
> replace a burned out relay.... Each relay would control a load
> around 1.5 A @ 120VAC, some resistive (the heaters) and some with
> fluorescent lighting. The heaters turn on and off every few minutes
> for 12 hours a day; say 100 cycles/day. The fluorescent lights turn
> on once a 12 hour cycle. It is possible that one of the relays may
> also run a small fan, although that's not currently the plan.
>
> A clutch of eggs is worth around $500 alive, and and nothing
> dead. :-) A few pennies on the proper protection for the relays is
> definitely worth it. I can't find any way to size the proper
> protection, other than "Watch for sparks and fiddle with the RC
> values until the sparks go away." What are people doing to protect
> against burned contacts?
Would you be able to use solid-state relays? Their drive requirements
are quite small, so the DIO port on the TS boards should be able to
drive them directly. You can also buy chassis-mount relays one at a
time, the exact number you need. This also neatly avoids the issue
with arcing across contacts.
Search for the Crydom CC1000-ND this is just one example of an SSR you
can get. Various load ratings are available, this one can switch
It also has AC zero-crossing switching, so the EMI will be
low (may help protecting the TS7250). I found it by searching for all
SSRs on Digikey with DC control inputs that operate down to 3V (which
is what the TS7250 can put out on its DIO port).
PS, interesting application :-)
-Jim
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