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Kai Klaas
02/09/06 18:36
Modified:
  02/09/06 18:42

Read: 1340 times
Germany


 
#109663 - Will work!
Responding to: Prahlad J. Purohit's previous message
Prahlad said:
The Red LED Vf=1.6V thus it wont allow any incoming singal >1.6V to go to non inverting pin of comparator.




Dear Prahlad,

if output voltage of transformer is zero, then, proper calibration assumed, potential at inverting input is nearly identical to reference voltage. In this case a voltage of 5V / (20k + 5k1 + 5k1) x 5k1 = 0.84V is dropping across the LED and current through the LED will be less than 1nA, which is totally negligible.

If output voltage of transformer is at positive maximum, on the other hand, then about 1.6V drops across the LED. At inverting input of comparator then a voltage of (5V - 1.6V) / (20k + 5k1) x 5k1 + 1.6V = 2.3V can be seen.

So, as Abhishek already mentioned, the circuit will work.

Kai

List of 13 messages in thread
TopicAuthorDate
Zero cross detector led. [ Kai ]      Prahlad J. Purohit      02/08/06 08:08      
   Yes, still required      Kai Klaas      02/08/06 19:50      
      Please Elaborate      Abhishek Singh      02/08/06 21:21      
      Input signal.      Prahlad J. Purohit      02/08/06 21:59      
         CMIVR      Kai Klaas      02/09/06 06:16      
            Input smaller than reference.      Prahlad J. Purohit      02/09/06 06:36      
               yes works      Abhishek Singh      02/09/06 08:07      
               Will work!      Kai Klaas      02/09/06 18:36      
                  Re: Will Work.      Prahlad J. Purohit      02/10/06 07:29      
         are you aware      Erik Malund      02/09/06 06:48      
            Searched entire page.      Prahlad J. Purohit      02/09/06 07:08      
               sorry, it seems to be gone      Erik Malund      02/09/06 07:46      
                  Re: LPCxxx App note.      Prahlad J. Purohit      02/10/06 07:37      

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