Snubber needed for triac driving heating element?

Usually a samll L- shunt C (10uH shunt 0.1uF) is added to eliminate excessive EMI from going into the mains, in which case you need a small snubber.

Thanks for the reply. The unit is to be a replacement for a mechanical timer that doesn't have any kind of EMI suppression.

At switch-on this is no different from a mechanical switch being turned on, except that a triac doesn't have contact bounce. Switch off will always happen close to zero crossings, so this is also better than a normal switch from an EMC point of view. You would not normally fit a snubber to a mechanical switch and there is even less need to fit one here.

John

You didn't say whether it is AC or DC. If AC you can add a zero crossing detector. In any case, check this out:

What type of device is controlling the on/off signal? It probably wouldn't be too hard to add zero crossing detection. But why bother? At 2 kW I take it this is a 240 volt heater? I'm guessing a UK tea kettle auto turn on for morning brew?

=========================

Must be from Plant Claire.

..... Phil

...and you must be from MARS! What a DOLT!!

You would not use a triac to control DC.

Flyguy wrote in news:513ab216-2eb5-4b4d-b50c- snipped-for-privacy@googlegroups.com:

Phil is 5 orders of magintude more intelligent than you are.

Which one are you trying to insult?

A simple digital timer switching an MOC3023 triac driver, probably a 4060 rather than a uC for such a simple job. The triac is a BTA41.

Exactly. I have random couplers in stock but not zero-crossing ones.

A convection (not microwave) oven for my daughter, a psychologist who sometimes dabbles in baking and is now really into it during the lockdown. The clockwork timer on her oven is behaving erratically. Indian 230V.

Ricky C wrote in news: snipped-for-privacy@googlegroups.com:

Good point. 5 decimal shifts on a zero is still zero. Funny to see FlyShit calling someone a dolt.

Only once.

Do not trust the TRIAC to stay off where it performs a safety function, though. A mains spike during the night might melt the TRIAC into a short circuit, and you could have the same experience as these people, albeit at a more reasonable price:

Whilst relay contacts can weld together and stay on when they shouldn't, still, I would have more trust in a relay than a TRIAC to stay off once the user (or a supervisory circuit) has confirmed that it is already off.

So the timer is a black box with some sort of output? I guess no option to add the zero cross detection in that.

You could just buy a contactor (relay). Simple and effective. They even have 240 volt relays with 12 volt drive. Maybe even 5 volt drive.

So 240 volts? Here in the US you can get about 1.4 kW from a 15 amp 120 volt outlet or 19 kW from a 20 amp outlet. Most kitchen stuff is 240 volts. Are you US or UK?

Why a timer??? Every oven I've ever owned has had a timer on it (seems obligatory somehow) but I have not once in 50 years used it. Can't she just set a kitchen timer and turn it off herself?

Where does she live? I'd like to go over for fresh baked bread once this is over. Or even just cookies. Mmmmm...

I've run out of not food exactly, but variety. So I should be going out today to shop. I am so sick of eating my own cooking. I believe I can get some carry out to bring home. I need to find some good restaurants near the store.

This is strictly for use in my household where all loads including TVs and computers are always switched off at the plug when not in use.

I'd prefer to use a relay, if only to obviate the need for a sizeable heatsink for the triac but I don't have any suitable ones. I do have some no-name 25A units but I wouldn't trust them to handle 9A on a regular basis.

But

ea

t-update-user-error

Strange. ?It?s a really wonderful feature to be able to re motely preheat your oven" Really? WTF?

Even if a triac were to trigger on from a power line spike, it doesn't stay on. It turns off at the next zero crossing. No? It would have to be a s cramble in the controlling circuit to make it come on for more than an inst ant which is what the Verge article is about. That can happen even with a relay.

? But

tea

eat-update-user-error

f.

Switching on and off a couple of times a day is not exactly a heavy duty wo rk load. Why not order a suitable relay? I've always liked the reassuring sound of the relay clicking which often helps isolate faults when the durn appliance isn't working.

I'll respond to the points you made here instead of interleaving them which I often find inconvenient to read.

Yes, it's essentially a blackbox with power in, timed power out. That doesn't preclude zero-crossing detection but it's not really necessary.

Re getting a suitable relay/contactor: ordering parts is not easy where I live even in normal times.

US or UK? Neither. I'm in one of the most remote corners of India which has little in common with the rest of the country. We use

So you never use the timer on your oven? No wonder you're sick of your own cooking. :-)

Where does my daughter live? You're out of luck - see above :-). So far she's produced cookies, pizza, cakes, doughnuts, ice cream and some experimental recipes without names. Yesterday it was roast chicken. Yummm. My wife's a good cook too, especially with local dishes.

BTW, my family - two engineers, one architect, the daughter, one daughter-in-law and one granddaughter - all live in the same house. This is not at all unusual in our society. The married ones will eventually move out but there's no hurry.