Modern Electronics (was Re: List charter mods & headcount... ;

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Jun 23 00:54:33 2004

>
> >So I yanked the whole
> >thing, wired the fan and magnetron together (I almost always used it on
> >high anyway, and lower power settings worked by imposing a <100% duty
> >cycle on the magnetron), and controlled it with an ordinary wall light
> >switch, on the principle that it's too simple for much to go wrong.
>
> A classic example of where a little knowledge can be very dangerous.
> Definitely NOT "UL Approved" or "CE Marked".

And that has _nothing_ to do with whether or not it's actually safe!.
Soory, but I've had enough of things that meet the standard to the letter
but are actually dangerous (those darn wall-wart PSUs spring to mind in
some cases), whereas properly designed stuff doesn't have the magic
letters on it.

>
> Lack of detailed core issues, presents a situation which is potentially
> dangerous. I would hate to think of the law suit you could face if someone
> comes over to your house and a fatal error occurs [your solution APPEARS to
> have bypassed all of the safeties (door, etc.)).

Very unlikely. At least in the UK, the interlocks on the microwave oven
door don't operate on inputs to the cotnroller board, they directly
switch mains to the magnetron transformer. That way, even if the
controller crashes (or the relay sticks, or...), the magnetron won't turn
on if the door is open.

My view (but I would wan to trace out a schematic to be sure) is that
it's perfectly safe to repalce the controller with a suitably-rated switch.


However, to tie this into the rest of the thread, I've seen some totally
lethal things by people who should know better (i.e. people with EE
degrees) and who didn't realise they were dangerous or that there was a
better way to do it. I am not talking about the sort of thing we've all
done on the workbench (mains on bare tags, etc while testing), I am
talking about finished devices with no earth, with earth and neutral
connected, with no isolation between mains and output, and so on.

-tony
Received on Wed Jun 23 2004 - 00:54:33 BST