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How does LM567 work without capacitor at pin1 ?

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tijoseymathew

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hi

I designed this circuit for obstacle detection. The ir led is switched at 4kHz by the PIC . this is detected by the photodiode and KX567 to cancle out interference. As you would have seen i have left out the capacitor at pin 1 of the ic. Still the circuit is working. but the datasheet recommends a greater thatn 1uf cap on pin 1. when i use the cap i get a continous high signal onthe output.

what could be the reason ?

will the circuit be stable at all conditions???
 

lm567 output

I think capacitor at pin 1 can't be related to sensitivity or PLL lock behaviour, cause it's output filter (delay function) only.
I append a reprocessed copy of your circuit. I recommend Irfanview for producing readable and compact pictures for the forum.

97_1203423345.gif
 

working of lm567

Hi,
That is the way the IC is supposed to function, that is when an in band frequency is detected, it will give a High level, otherwise a Zero. If you want to send data, one method is to key in the transmitter (On/OFF) with the data bits and you will receive corresponding pulses at the receiver. You can actually gate the transmit frequency and data bits through an AND gate and give it to the IR transmitter.
Regards,
Laktronics
 

ir led circuit using lm567

thanks but that doesnt explain how the ic works without a cpacitor at pin 1.
 

lm567+projects

Hi,
Please explain what you mean by IC working with out the capacitor, what kind of output you are getting?
Regards,
Laktronics
 

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