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???
06/07/06 13:42
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 		 #117950 - I don't think it's solved...
Responding to: ???'s previous message
Ganeshan said:
I have implemented the solution you suggested, with slight modifications.

Can you publish your circuit?

Ganeshan said:
The existing cable had to be used and a separate shield was not possible. So, stray noise affected RESET was still coming.

It's not so much the shield of cable which helps to suppress noise, but more the low pas filter at input of 74HC14:



So, if you still have noise affecting RESET, then you probably haven't chosen the proper time constant of low pass filter?

Ganeshan said:
Since I had a port pin free in 89C51, I used the same to control CLR input of one shot. With this, Pulse generation of one shot gets blocked until 89C51 decides what to do next and then releases CLR input. With this, the system is working consistently, independent of cable length.

Yes, providing a time window to allow resets is a good idea, but no solution of your noise problem, I believe. You will minimize the number of occurences of malfunctions, but not eliminate the basic problem, means the noise.

Tell us please, how you have modified the circuit, what low pass filter you use at input of your monoflop.

Kai

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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