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From: Fred Bloggs
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Subject: Re: how to reduce noise from 555 timer...???
References: <3E047B0F.firstname.lastname@example.org> <email@example.com>
Date: Sat, 21 Dec 2002 17:18:34 GMT
NNTP-Posting-Date: Sat, 21 Dec 2002 09:18:34 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
John Fields wrote:
> On Sat, 21 Dec 2002 14:29:52 GMT, Fred Bloggs
>>Hang a Schmitt trigger or other high impedance comparator off the timing
>>capacitor node of 555 and use this to clock the 574 at Vcc/2. This will
>>allow you to capture valid data before the circuit is nuked by whatever
>>it is that's causing the problem. The 333ms is ample time for recovery
>>and you can continue to use any grade of timing oscillator.
> It's generally bad practice to try to circumvent a problem instead
> of determining the cause and curing it at the source.
> There is _no_
> reason why the 555 shouldn't operate satisfactorily in this
> application, especially with all the CMOS 555's available now.
I agree- the logic is so fast that the analog front end and A/D are
effectively sample and holds- where he captures data derived over the
previous 100us microseconds for the ADC0801! There are many examples of
systems where something with the operation severely interferes with
sensor operation, and timing like I have suggested is used to circumvent
the problems. And the OP states that only the 4460 "swinging same
freaquency"- like so what?
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