Window Comparitor [sdiy] 3 bit A to D with hysteresis?

[Cynthia Webster]

Hi Batz!

Funny, after reading the criteria,
 a window comparitor was my first reaction too!

So either you're Not crazy...
(or we Both are) LOL!

I remember some time back seeing an adjustable window comparitor schematic
that I thought would make a very nice Serge-ish type module, and wonder if
you or anyone else has a good (read: bulletproof)  circuit for one?

Warm Regards!

Cynthia


on 5/26/02 12:28 AM, Batz Goodfortune at batzman at all-electric.com wrote:

> Y-ellow Paul 'n' all.
> 
> At 05:48 PM 5/25/02 +1000, you wrote:
>> Can anyone point me to a 3 bit A to D with hysteresis?
>> (yeah I now I can do it with a PIC! but, there must be an elegant
>> alternative.. eventually I want to be able to select between 8 inputs by a
>> control voltage, but without problems of 'jumping around' on the edges of
>> the changeovers.)
> 
> What about this. This is just an idea. Not properly formulated or anything
> and probably a little high on the parts count but!
> 
> Make up a standard sort of 3 bit flash converter (8 opamps/comparitors with
> resistance ladder) but the twist being a window comparitor on each one.
> (Maybe get away with it somewhere further forward in the chain I'm not
> sure.) The thing could only switch when the voltage is in the window. WHen
> it's between windows it can't flip up or down.
> 
> I think it's a window comparitor you're needing here. In that you can set
> the hysteresis on both sides of the window. The only way I know of building
> a window comparitor is with a pair of op amps. So that would be 16 op amps
> for your 8 level/3 bit flash. But perhaps with a little experimentation you
> could cancel down using the hysteresis from the level above or something?
> Perhaps using some kind of lock-out. IE: An analogue AND function? IE: can
> only spit a bit if the one below it is out of it's range.
> 
> Does this sound plausible? Even in your wildest dreams?
> 
> A PIC or an AVR or something would of course be a far cheaper solution. But
> who wants to program one.
> 
> Hope this helps.
> Be absolutely Icebox.
> 
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