discharging caps

But a resistor plus an inductor could give a critically damped decay, which would be quite a bit faster. I don't know enough about the circuit to be prepared to try to work out how much inductance you'd need, and you clearly can't be bothered.

But you don't do circuit design, and this sort of question makes it obvious why you don't.

Electric chair, sell it to trump?

Connect the incoming supply with a short length of solder wire close to the resistor.

If the circuit is fed with DC, without access to the incoming AC supply, how will you detect mains failure? If you have half a volt to spare and you put a diode in the supply line, then you could use a voltage relay as a detector on the supply side of the diode. You could actually power a normally-closed contactor directly off the supply.

The circuit then becomes extremely simple (and less error-prone), needing only a contactor, a diode, a solder fuse and a resistor.

(It is often a good idea to include a diode anyway; it will prevent damage when the supply connections are reversed, as they almost certainly will be, despite every precaution.)

No relay, use an thyristor

No doubt you could calculate the correct resistor value, discharge time, and other parameters, but need to specify what is the target performance, which hasn't been specified.

Great idea, but the a relay and resistor combo is about as simple as it gets, and if you are really paranoid, use two relays.

You could also use a thyristor, but then you have the complication and possible reliability issues of a triggering circuit.

What you really seem to be asking for is a constant current discharge profile. Only way to get that at that sort of power level, is use a pwm igfet / mosfet circuit in series with a load resistor, but oh, the complexity.

Not all solutions can be elegant :-).

I'm not sure that a length of solder wire would make a very safe fuse. You might end up with a spectacular arc. John

It would be better not to use a flux-cored solder because of the extra ionisation this might create but it wouldn't be carrying a fault current, just breaking the charging supply. Plain lead wire was used in fuses on D.C. systems for many years without problems.

I said what I want to do in my original post: discharge 0.2F charged to 200v, in a couple of minutes. Later posts clarified that I want it to be safe and foolproof and discharge all the way.

I can't think of a simple, safe way to drive the relay coils.

And how do you think the relay contacts should be wired? Would a coil failure discharge the caps, or would it not?

And a thyristor would stay on once it was triggered.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

If it got a glitch, It would latch and keep the discharge resistors on, even if the power supply was still up.

Brownouts are difficult to analyze, and dangerous.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Besides safety, would you care to name them? Or is this 'problematic', as in I'm too lazy to get into it, or the decision isn't mine to make.

One of your basic problem specifications IS the time element, if discharge is mandated.

There are regs covering warning indications of all types. Hot surfaces, voltage, energy, pinch points, radiation etc. Refer to them. They vary for user accessible or maintenace-only accessible locations.

Just because you think you're doing it right, doesn't mean that you are. Good intentions sometimes are just not enough.

I think we can all safely assume that this one of the things you're attempting to avoid. Or is this a funny joke?

As long as 240V (European?) incandescent lamps remain commodity.

Incandescent (PTC) elements won't work in series, so no 120V hardware doubled up.

Aaaahh . . it's the red hot business that shortens their life. Or were you making another funny joke?

We prefer that you think about it, before posting.

Or buy a real fuse.

Something like that would work. I'd need a big diode with a heat sink, but that's not a show stopper. The power supply is programmable/variable, so the contactor would have to work over the voltage range. That's managable too.

Yikes. Let's hope not. The power feed is connectorized.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The most common form of maintenance safety feature of high energy installations is a 'lock out' feature.

This can be a simple hatch-activated switch that enforces various internal on/off features, such as motor de-energizing or energy storage discharge.

Consult the relevant literature.

RL

Of course I'm a circuit designer. I've posted tons of circuits here.

Maybe my favorite is my instant-start LC oscillator. The latest one,

Another recent one, the 50 cent DDS, ain't bad.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Test it carefully first.

It didn't take long for an idiot to mention DT in a circuit design thread. Whatever turns you on.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

Won't be bothered.

The inductor suggestion is hilarious. Thanks.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

The life of an incandescent lamp is inverse on about the 12th power of voltage. So running red would make them last thousands of years.

A standard/legal firecracker is roughly 200 joules. A kilojoule can do serious damage. Lawrence Livermore considers 9J to be the threshold of lethality.

Post a circuit. Sarcasm is cheap and easy.

It's shocking how many people can't design circuits these days. I think the semiconductor people scoop up all the good kids.

John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics

You wanted a load ! Criminals have been a legal load as punishment in the YouASh for years.

A bit touchy, aren't you? Fussion fan

Bye the waaay You can use 2 thyristors, one to switch that chair on, and the other one in series with the power input functioning as diode that only is allowed to go on when the discharge of your chair is complete, easy one for a smart designer like you, just a few components.

Unlikely that both relays would fail at once. Both contacts in parallel across the caps and series load resistor.

If the relay contacts are normally closed, open when energised, it would need few parts or an aux relay contact pair each, to detect an open circuit coil, or faulty contact pair.