Looking for two-input comparator with hysteresis

That's the way they all were, up to about 20-30 years ago. ;-)

Cheers! Rich

There are clocks that run off of and count the AC line, but cut over to battery power and a crystal oscillator during AC power failures. The AC line is far more longterm accurate than any affordable crystal oscillator.

John

Cheers! Rich

I think the idea was that line glitches could give false triggers, and if the comparator doesn't have hysteresis, it could oscillate during the relatively slow transition at 50 Hz. I did this with an LM324 once, and didn't bother with hysteresis or anything, but it was only used to start an 8.333 ms timing loop, so any glitches (if there actually _were_ any - I can't verify or refute that) were locked out in software.

I wonder how long the OP is going to keep this thread going before he actually tries any of these suggestions?

Thanks, Rich

They aren't the _only_ thing that matters, but they're not to be dismissed out of hand. ("I've got a bad feeling about this..." "Oh, go ahead. Feelings don't matter!" "OK, here goes - AAIIEEeeee-")

Thanks, Rich

How about "Shot-key"? I knew a Dutch guy once, who somehow stuck a K in the middle of it.

Thanks! Rich

Hello Keith,

Yeah, ol' Max took the wind out of the sails of us analog guys.

I had a fairly long chat about this with John Larkin. Whilst I acknowledge this is acceptable I simply prefer not to do it. There's some 'history' behind my reasoning.

Yup.

Graham

And this is relevant to an electro-mechanical clock exactly how ?

Graham

For a *battery* powered clock ????

Oh yes. Definitely.

Graham

One should always be skeptical of learning from experience.

John

I have one that's similar except it runs of a 'crystal' all the time. Wish it didn't. It's cheap and drifts with temp. Only stays accurate @ around 20C. It's just enough drift to be annoying. Also the battery backup seems to have enough leakage to drain the battery before you ever need it ! Doh !

Graham

Battery backed up, sure. The OP was connecting to the mains though.

Mainly because if someone has to ask these questions I assume he's out to kill himself. *I* suggested the opto. Others think it's superfluous. Maybe, but not knowing the OP...

Show me where the OP is building a cheap consumer product?! You ass-u-me quite a lot!

...and this is a bad idea, unless the manufacturer specs their use in this way (as Xilinx does).

AC line.

Not necessary if the clock is a uC.

I meant literally a battery operated appliance. Not the OP's clock.

Graham

not

I'm applying the thinking that would go into such a device in large scale production. It's not unsafe in any way,

Graham

not

It *IS* for anyone who has to ask these questions. Maybe you should read the thread rather than shoot from the hip, again.

that's not

I read the thread comprehensively. The OP was in fact doing exactly what I recommended. Maybe you should instead read what I said ? You'll find I inserted all the appropriate caveats.

Graham