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???
02/23/09 07:33
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 		 #162681 - description of project
Responding to: ???'s previous message
actually i want to count the number of revolutions of a toy-car wheel.i've put a hole in its gear and used a led,ldr combination to count the pulses.the output of ldr varies from 2-7volts.i want to count how many times it goes beyond 4 or 5 volts in order to count the number of revolutions.i hope now u'll be more clear about the problem.please help me with it...

List of 27 messages in thread
TopicAuthorDate
comparator with 8051            01/01/70 00:00      
   What have you tried?            01/01/70 00:00      
      description of project            01/01/70 00:00      
         Look at photo transistor            01/01/70 00:00      
            further description            01/01/70 00:00      
               But why 7V ?            01/01/70 00:00      
   Another project?!            01/01/70 00:00      
      this is another project            01/01/70 00:00      
   Not a sinusoidal waveform!            01/01/70 00:00      
      Well, it can look like a sine...            01/01/70 00:00      
         still problem with comparator            01/01/70 00:00      
            Circuit missing            01/01/70 00:00      
            sorry the circuit is here            01/01/70 00:00      
               the circuit            01/01/70 00:00      
                  Why bandages, and why 9V VCC?            01/01/70 00:00      
                  VREF is wrong!            01/01/70 00:00      
               How is Vref 4V ?            01/01/70 00:00      
            used two diodes at input to MCU            01/01/70 00:00      
               Doesn't solve the Vref problem!            01/01/70 00:00      
   kai, help me with comparator            01/01/70 00:00      
      Give this a try...            01/01/70 00:00      
         thanks            01/01/70 00:00      
         thanks, the circuit worked            01/01/70 00:00      
   LM339 is an open collector            01/01/70 00:00      
   As Aamir Javaid said about input to 8051.            01/01/70 00:00      
      Not for an open-collector output!            01/01/70 00:00      
         Is that tied to +5VDC            01/01/70 00:00      

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