How much reserve needed in power supply diodes? Sunday Night Electronics...

Me | 2/3/2024 | Paul R.

[Paul R.]

My brother’s 750,000 volt Tesla coil got me one time. Knocked me on my butt. Luckily, there was not a lot of current behind it...

[JustaTech]

You could always adapt or build a PWM controller driving an H-bridge, to give you an infinitely variable temperature control.

[Lockbox]

"Are you sitting in a bean bag chair, naked, eating Cheetos!"

*Yes, sir!* "Do you feel the urge to get up and send me a thousand dollars?" Close! I thought he was talking about me there for a second.

[Paul R.]

Maybe I should have called this the “Fireworks Night” thread. And I was off by a day - geez!

[Chode]

feel the lightning...

[Paul R.]

I usually double the expected rating.

Seems pretty reasonable.

Sending a PM shortly... (Just a "funny")

[Revel]

BTW you basically will have no CEMF from a heating element. Therefore your reverse voltage only has to be at the peak of the AC line voltage. So for 120 volts RMS you have a Peak of around 170 volts. So a Diode with a 200 volt reverse voltage would handle it.

[KarlInOhio]

During the time when the diode is on, the full half wave current will be drawn. The average voltage and current (RMS actually) are your quoted 120 volts and 12.5 amps. However at the peak of the wave will be 170 volts and 17.7 amps. Even with the diode in the circuit, you will still get those values in the active half of the cycle.

Even if you plan to use this only when you are running with one element, you still have to make sure you can handle both, unless you build this inside the heater after the switch.

[KC Burke]

Sounds like the electronics are a second level challenge.

The first level challenge will be the ladder ballet.

[trebb]

I would tell you, but then I’d want a cut of whatever market you manage to corner....😁

The only rectifier I ever built was a 4-diode full wave to charge my battery when the voltage regulator in my Fiat went out - and I would have had to buy a while new alternator to replace it - just used the biggest diodes I could find in our bench stock....

[mabarker1]

You’re Grounded !!!

[mabarker1]

Why

[mabarker1]

[Chode]

lol

[Texas Fossil]

I have some large oil filled caps. You don’t play hot potato with them. They are heavy. They don’t leak voltage.

[Texas Fossil]

They are good for solar power applications, because of the low voltage drop.

I keep quite a few of them on hand.

[Paul R.]

Correct!

[Paul R.]

Heh, 2nd comment to that effect.

In this case the prospective market is just me.* This diode technique to provide “half power” is, as I mentioned above, used in maybe 20% of the quart” heaters on the market.

Basically, if you see all the elements dim on “low power”, vs. “high”, a series diode has probably been switched into the circuit. More commonly, the heat setting is determined solely by the number of elements running full blast. I have a different floor standing quartz heater with 3 elements, so the user can turn on one, two, or all 3. Each element is ~500 watts.

*That said, I just now ordered my 20 pcs. of 20 amp diodes. So, I can modify a couple other heaters too, maybe even that 3-element unit. I don’t “need” 6 heat settings, but, as a preventive measure to extend the lifetime of both the elements and (using the controls wisely) the thermostat, it might well be worth it.

[Paul R.]

You punny! :-)

[Paul R.]

I never thought to wonder, are there “Schottky” transistors? In some uses I can think of, a low voltage drop at the p-n junction in a transistor could be useful.