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Old 08-04-2018, 06:00 AM   #41
stj
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Default Re: Oven broiler stuck on!!!!

if tolerence mattered, they would not be using electrolytics
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Old 08-04-2018, 09:41 AM   #42
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Default Re: Oven broiler stuck on!!!!

It's working and maybe should have tried one of those arc suppressors. It's sparking pretty good when it disconnects still.
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Old 08-11-2018, 05:38 AM   #43
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Default Re: Oven broiler stuck on!!!!

Hmmm.... I just had an idea

What if you get two more powerful relays and put them on each side of the heating element (i.e. in series), so that they both switch on and switch off the element. I think that should help to reduce the spark, even though both relays will likely turn off at slightly different times due to small differences in the coils and whatnot. And if not, you still get more redundancy - that is, if one relay fails with stuck contacts, at least the other one should continue to power off the heating element (... until both get stuck contacts? ).

Of course, some big polypropylene caps should also help reduce the sparking too, I think.
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Old 08-11-2018, 11:09 PM   #44
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Default Re: Oven broiler stuck on!!!!

A T92 is a good high-current relay. It makes heat due to the contact resistance, so the crimp-connector version sucks due to extra heating at the spade. I think it's good to 20-25A. max. before it runs too hot.
It's also DPST; so one contact is always getting the arcing as they are never perfectly matched mechanically. You would then need two snubbers, one for each contact.
Heating elements have a lot of inductance. I find even 10nF caps help tremendously. Maytag stove burners would get stuck on the contacts would get stuck and the cap fixed that, but leakage current now at the element.


I did a long-life 32A heater design that used both an SSR to switch on/off power and a mechanical relay to bypass the SSR.

SSR on, 50msec later, mechanical relay on.
Mechanical relay off, 50msec later, SSR off.

Since an SSR dissipates about 1W per amp, shorting out the SSR keeps it cool. The mechanical relay never switches load on/off, so it lasts a very long time. This was to meet a 100,000 cycle lifetime safety standard.
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Old 08-12-2018, 04:12 AM   #45
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Default Re: Oven broiler stuck on!!!!

the ssr should still need a snubber.
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Old 08-13-2018, 01:07 PM   #46
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Default Re: Oven broiler stuck on!!!!

Yes, need a snubber regardless of SSR or mechanical relay.

At the very least, I find 10nF-68nF X disc cap across the contacts stops arcing from wrecking the relay contacts.

Lots of appliances could use the mod.
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Old 08-15-2018, 10:15 PM   #47
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Default Re: Oven broiler stuck on!!!!

Hopefully these last another 18 years. May have to do something if I need to get into it again. The one seems to still be in good shape.

Although I kinda wonder how crappy things will be then.

Last edited by junktv; 08-15-2018 at 10:16 PM..
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Old 08-16-2018, 06:39 AM   #48
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Default Re: Oven broiler stuck on!!!!

in the future the chinese will probably sell you a relay-shaped pcb with an smd fet & driver on it.
they already have that in the casing of a lot of car relays now.
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Old 08-16-2018, 03:08 PM   #49
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Default Re: Oven broiler stuck on!!!!

I recently got a card reader that cost less than shipping.Seems legit. It does look "close" to pics.

Last edited by junktv; 08-16-2018 at 03:10 PM..
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