--- In "Alejandro Weinstein"
<> wrote:
>
> On Wed, Oct 29, 2008 at 2:24 PM, Jason Stahls <> wrote:
> > Yan Seiner wrote:
> >> Anyone know if I need MOVs/zeners on fluorescent lights?
> >
> > You shouldn't need them, the transformers in the balast
shouldn't create
> > that much back EMF but it's not a bad idea anyways. You never
know when
> > someone might want to connect something else, or worse connects
> > something inductive not knowing that they need MOVs...
>
> Since you are using AC, I think you need to use an RC snubber, not
a
> MOV/Zener/TVS.
>
> Look at http://en.wikipedia.org/wiki/Snubber#Electrical_systems.
In
> particlar, they say:
>
> "In ac circuits a rectifier diode snubber cannot be used; if a
simple
> RC snubber is not adequate a more complex bidirectional snubber
design
> must be used."
>
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?
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