115/230V voltage switch key for transformer?

"Joig?" Or maybe "Yoig?"

If "Euler" is pronounced, "Oiler," then howcome "Euclid" isn't pronounced "Oiclid?" ;-)

Thanks, Rich

PS. I was thinking maybe "Yerg". ;-)

Oops - I think the vodka might be kicking in...

Thanks, Rich

See if this will work for you.

I was thinking about putting the wall wart elsewhere and run your widget off DC.

How about using your 240V transformer (or dual primary in series) with a secondary voltage high enough at 120V to run your switcher or perhaps a buck-boost switcher. Let it run at 1/2V at 120V.

The universal supplies are such a nice idea..

~100 .. 240 volts input. etc...

Some start as low as 24 volts AC/DC

(snip)

If you do go that route, beware the brownout on a 240V supply. Kills auto-select ATX PSU's.

Probably I could get a DPDT 250V-rated for under a buck but the cap would need to become larger. Then I'd have to convince TUEV and other guys that this is all nice and kosher.

Yes, there is a cap but this all adds parts and stuffing costs. Pretty soon you are over the one buck.

Ahem ... I think it was in France where a TV team plugged in some Klieg lights and then the wallpaper turned black from ceiling to wall outlet. Turned out the circuits did not have any fuses and the custodian said "That's normal around here".

Don't know how old she is but it might be great to include your daughter in the design process as well. Who knows, maybe she'll catch on to engineering.

Do you remember where or what brand it might have been?

No, the o-umlaut is like the first part of the French word for "maybe"

-> peut-etre

Technically one of the "e" needs a roof over there but my keyboard can't do that.

In German it is :-)

Na'sdarovje!

Thanks, Herman, I've copied down those Molex part numbers. I had pondered a key plug before but not looked at Molex yet. The crimping labor would have to be added to the 79c. Possibly that can be handed off to a place that specializes in it.

I'd love to but transformers operated at much lower than rated voltage become "soft" and you can't get the rated wattage across.

Yes, but when you inquire about the fine print it turns out they must be derated at rather lowish temps, starting around 120F. That kind of rules them out in this case.

"Partially let go"? Given that the magnetic force drops very steeply as the iron moves away from the pole piece, I'd have thought that a very remote contingency...maybe it just moves too slowly for the arc to be extinguished? Please expound.

Cheers

Phil Hobbs

It's an old lesson that I learned after building my first RF power amplifiers (kilowatt-class). The T/R switch relay had to be controlled with gusto when doing very fast morse code sequences where you get close to realtime switching, else its contacts would erode rather fast. IIRC I went through almost a dozen Potter&Brumfields over ten years back then.

A transformer presents to some (small) extent an inductive load which likes to arc a bit on anything that mechanically opens and closes. So in this case you'd need some circuitry that cuts the relay loose instantly, like a threshold detector. It's all doable but at some point the costs kind of add up.

The main problem with power relays is often when they want to come back on. A contact that sluggishly leans into its counterpart can easily cause a brief "bzzzt". If that happens a lot it's like a pinging engine, it causes wear. This is why the HV guys spend so much effort to speed up the action in their contactors. It's a whole science in itself. At the power electrics institute of my university I had seen some really nifty prototypes, such as contactors where a pressure capsule was used to give them gusto. Every time they switched you heard a bang from that pressure-assist mechanism, to the point where they required people to wear ear protection.

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Sorry I don't really remember what kit it was in !

I do remember being curious enough to take the cap off to have a look and put it back on the wrong way round, blowing the mains fuse. A 30mm

Imagine 8 jumpers side by side in a single molding.

That's exactly what I am looking for. But it's like a looking for a needle in the hay stack with the chance that someone already took the needle away :-)

Have the factory set the jumper, then stick one of those "warranty void if this sticker is removed" stickers over it?

Good Luck! Rich

And then some kid does it anyhow, it goes wrong, and plaintiff claims the kid couldn't know because it wasn't printed on there in Swahili and wants the jury to "award" a couple million :-)