The ohnosecond

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A "gull-winged" SMD package, gets a bigger distance between the pads too.

Getting the optos to have enough isolation turned out to be the easier part of this problem. Finding PTC devices is one of the harder issues.

The most curious was that the diodes that were supposed to be 600V that all failed at 150V give or take a few.

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kensmith@rahul.net   forging knowledge

In article , David L. Jones wrote: [...]

If the designer included an "anti-oops" diode, reversing the polarity would result in that sort of "ohno" but not my sort of "ohno" hence I prefer my version of what an ohnosecond is.

BTW: adding a diode to the coil circuit on a relay almost works. The diode will rectify AC and pull the relay in. Bizzzzttt poof

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kensmith@rahul.net   forging knowledge

In article , Adrian Tuddenham wrote: [..]

That would make the PCB taller by having things stand up from it. Its a good idea in general but in my specific case, the added height is a problem.

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kensmith@rahul.net   forging knowledge

Ah, pity.

I rather like the idea that lovingly hand-soldered tagstrips still have a place in modern electronics.

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~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

Hello John,

And about creepage distances, at least when it comes to IEC601-1.

The environmental conditions play a huge role in all this. Pollution, humidity levels and so on.

Regards, Joerg

Hello John,

That is now. But where will that board be used? In an industrial environment with smoke stacks, diesel forklifts and the boss walking through there with his stogie leakage can very be different after a while.

Have you considered potting up the sensitive areas?

Regards, Joerg

The CAR collided with the train? Like trying to cross the tracks while the train was moving along them?

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you left out management........

martin

I heard that aircraft black boxes have very similar endings to the cockpit voice recordings. Lots of very rapid jabbering in whatever language, then "OH SSSSHHHHHIIIIIITTTTT!!!!!".

In the spirit of the ohnosecond, I propose the ohshittosecond for the length of the time it takes to realise yes you really are not going to get out of this one and you hope you are going to die faster than the 200 milliseconds delay between reality and human perception.

The shittosecond is a similar (but not necessarily fatal) period it takes to realise buttock clenching is not going to save your underwear.

Hello Martin,

And you left out Marketing. No matter what the performance is they'll advertise it along the lines of "With these socks you can fly all the way to the moon".

Regards, Joerg

In article , Joerg wrote: [...]

Just for fun I set up a little experiment. I'm using an FR4 PCB without mask.

Gradient = 23KV/inch RH = 100%

Its has been powered since 10:32AM today.

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kensmith@rahul.net   forging knowledge

Don't pot. Put the whole thing in a sealed housing. Unless you are making millions, potting is rarely worth the bother.

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kensmith@rahul.net   forging knowledge

In article , Adrian Tuddenham wrote: [...]

They do still show up from time to time. The little turret standoffs are also still used.

It has been a while since I saw a "ground star" used in anything.

Large tube sockets still find a use from time to time.

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kensmith@rahul.net   forging knowledge

Hello Ken,

Ouch. I'd make sure to turn it off before you go home or the insurance adjuster may have some uncomfortable questions ;-)

But it does corroborate the med regs somewhat. We usually have to maintain 8mm (about 1/3") and the peak defib voltage is 5kV. That is with a lot of margin.

Regards, Joerg

Hello Ken,

A sealed housing can get expensive. I depends a bit on the layout of the board. If you manage to keep three sides free of anything that needs to connect potting becomes quite easy. Dunk it in, let dry, done. Of course, repair will be quite a challenge afterwards.

We did that with hybrids and it wasn't millions. Just about 35,000 per year.

Regards, Joerg

I had an ohshitosecond right before my car collided with a moving train. Thanks to the seatbelt, I walked away with minor bruises. The car though, was not so lucky.

i

exactly. I was tired, did not realize that I needed eyeglasses, it was dark and the crossing was unmarked.

i

I still find the "Mitcham Tagstrip"[1] useful from time to time.

[1] They are made by coiling a length of 22SWG tinned copper wire around a 0.125" drill shank (or other convenient mandrel) and cutting off short lengths. The component leads are all shoved into these 'spring' tubes and soldered in the usual way.

They are used: a) To join two components end-to-end b) On a conventional tagstrip to increase the number of components which can be joined to a tag c) If the wire to be joined is difficult to solder, they form a 'solder pot' around it.

They were used a lot in pre and post-war Philips equipment built at their Mitcham factory.

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~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

I read in sci.electronics.design that Adrian Tuddenham wrote (in ) about 'The ohnosecond', on Tue, 8 Nov 2005:

And in Kolster-Brandes radios, made at Footscray.

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Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk