How to detect power cutout for PC?

Graham,

I don't know why you are missing this, but what you present as fact is blatantly and repeatedly wrong. You seem so intent on making belittling comments - maybe that's why you are missing it. If you breadboard the circuit you'll be able to see the delayed relay dropout with the cap. Or if you rely on your opinion of the poster instead of math or breadboarding, then think about what John Woodgate or Rich Grise said concerning the delay. I assume you have a high opinion of them?

Ed

I'd got confused over what kind of delay was wanted !

It still won't work for long - as you noted.

Graham

yeah, but whay are you going to power the relay with, another plugpack plugged into the UPS ?

back to the original design something can probably be done using an optocoupler instead of a plugpack and relay, but a home made a cable with a mains plug on one end and a serial plug on the other might get some strange looks....

hmm, what's the best way to power the LED in an optocoupley from the mains, a big honking resistor or something more subtle?

C1 || ___ L--[680R]--||---~ /\\ ~ || / \\ 250v +--|->---+-----+ 50Hz | \\ / _L_ | N-------------(--_ \\/ ~T~ \\ / LED | ~~ ~ |10u ~T~ (in opttocoupler) +-----------+-----+ now for C1 hmm 730V swing 100 times per second wanting to pass 10mA or slightly more 0.01/(730x100) = 0.139 uf rated for 250VAC

I can get 200nF seems to be a standard size

the 680 ohm resistor is there to stop the power-on surge (if ppower comes on at one of the peaks of the AC cycle) from destroying the diodes in the bridge... probably should be rated for 400V but only needs to be a 1/4 watt part... the bridge needs only to be rated for 500ma and 5v1

maybe a fuse would be a good idea too, eg, 250AC 100ma

comments anyone?

Bye. Jasen

In article , Rich Grise wrote: [....]

How about a Sidactor from Teccor. They are very spiffy spike catchers.

Yes

If you are reading it at a hardware level it isn't much of a problem. At a higher level, the OS may filter out overruns.