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Article #15966Re: How would you detect lack of a square wave?
From: John Whitmore
Date: Sun, 03 Jan 1993 23:21
Date: Sun, 03 Jan 1993 23:21
33 lines
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1790 bytes
In article <1993Jan2.172332.21070@socrates.umd.edu> jimbo@socrates.umd.edu (Jim Bogard) writes:
>What's the best way to detect the presence/lack of a square wave?
One way is to use a 'missing pulse detector' with
a one-shot (which has already been mentioned). Another,
more common in cheap consumer gear, is to use a transistor
and rectify the AC...
+5V
|
R
|
+------+--------output
| |
= /
| |
in+-------||---+---|>|----+----|
| |
- \
^ |
- |
| |
GND GND
The input capacitor pumps charge through the
two diodes to turn the transistor ON, and the collector-to-base
capacitor keeps the transistor from turning OFF quickly
(until the next pulse comes in). It is even possible to
omit the diodes in some circumstances. The input and output
voltages needn't be limited to logic levels, either.
John Whitmore
Technical Details
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Path: arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!rpi!batcomputer!cornell!uw-beaver!news.u.washington.edu!carson.u.washington.edu!whit From: whit@carson.u.washington.edu (John Whitmore) Newsgroups: sci.electronics Subject: Re: How would you detect lack of a square wave? Date: 3 Jan 1993 23:21:42 GMT Organization: University of Washington, Seattle Lines: 35 Message-ID: <1i7se6INNr2b@shelley.u.washington.edu> References: <1993Jan2.172332.21070@socrates.umd.edu> NNTP-Posting-Host: carson.u.washington.edu