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???
06/09/06 03:29
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#118066 - They're a crutch ...
Responding to: ???'s previous message
They're a weak crutch for people who can't design logic just as optoisolators are a weak crutch for people afraid to use transistors.

There are conditions where it seems simple, so we're all tempted to use 'em, but DON'T GIVE IN TO TEMPTATION.

Anyone who's used 'em quite a bit and had to troubleshoot his work knows that they don't behave well when probed with a 10-Mohm probe, and their trailing edge moves around like crazy. Not only their trigger, but also their reset and timing circuits are sensitive to noise, and I mean noise levels as low as 1% of the supply. DON'T RELY ON 'EM.

If you need a one-shot, you can run a counter that gates itself off at a certain count, using the reset line as a trigger. That's at least as good as any one-shot and not nearly so fussy.

RE


List of 36 messages in thread
TopicAuthorDate
Cable Capacitance Problem ?            01/01/70 00:00      
   Theorizing? this should be fairly easy t            01/01/70 00:00      
      Yes. Lamp is turned OFF and ON            01/01/70 00:00      
         I take that this is simultaneous to my a            01/01/70 00:00      
      The one-shot is probably a factor            01/01/70 00:00      
         Schematic upload - how to do it?            01/01/70 00:00      
            Here is the link            01/01/70 00:00      
   Lamp is working like PTC            01/01/70 00:00      
      in the olden days, they were called URDO            01/01/70 00:00      
         Thanks for the explanation.            01/01/70 00:00      
            because            01/01/70 00:00      
   I miss the urgently needed bandwidth lim            01/01/70 00:00      
       I agree, the idea was too simplistic            01/01/70 00:00      
         peanuts...            01/01/70 00:00      
            I'd say            01/01/70 00:00      
      Working Solution            01/01/70 00:00      
         I don't think it's solved...            01/01/70 00:00      
            Details            01/01/70 00:00      
               Hello?            01/01/70 00:00      
                  try this, try that, go broke            01/01/70 00:00      
               In many companies, it will get you fired            01/01/70 00:00      
                  expanding            01/01/70 00:00      
                  Just debating            01/01/70 00:00      
                     They're a crutch ...            01/01/70 00:00      
                     so called professionals that believe tha            01/01/70 00:00      
                     Monoflops            01/01/70 00:00      
                        burnt child shy fire            01/01/70 00:00      
                        If you are careful, they might work.            01/01/70 00:00      
                           not very good odds            01/01/70 00:00      
                           Being careful...            01/01/70 00:00      
         not noise supression            01/01/70 00:00      
   does the ULN(can't read the numbers) dri            01/01/70 00:00      
      ULN2003            01/01/70 00:00      
         I did NOT ask for the part number, I ask            01/01/70 00:00      
            By other words...            01/01/70 00:00      
               Books don't say all this.            01/01/70 00:00      

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