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What is the Capacitor value to put here?

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Suraj143

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Hi guys I’m going to connect this circuit to the telephone line. Can you tell me what’s the capacitor & resistor value must used in this circuit?

Can I use a 0.1 uF 250V ?

Thanks
 

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Hai Suraj143,

Try a 0.47 /250V dc or 160V AC -- Polysterene or polycarbonate type caps.there are BOX type caps in the market. you may recover from your unused or scrap also a cap of similar type.

Sarma
 
Thanks a lot mvs sarma is there any relationship with the value that I use.

I'll try to place a 0.47/250V cap.But can I place a 0.1/250 V cap?

here is the picture of what I have.It's a 0.1/250 V cap.

thanks
 

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Suraj143 said:
Thanks a lot mvs sarma is there any relationship with the value that I use.

I'll try to place a 0.47/250V cap.But can I place a 0.1/250 V cap?

here is the picture of what I have.It's a 0.1/250 V cap.

thanks

hi,
The 1uF cap has a capacitive reactance to the 'ring' signal frequency, 10 times lower than the 0.1uF you are considering.
Its therefore possible with a 0.1uF, that you will not drive the opto-tx hard enough to trigger the opto detector.

You could try the 0.1uF on the bench, it will not damage anything within the circuit.

Eric
 
Suraj143 said:
Thanks a lot mvs sarma is there any relationship with the value that I use.

I'll try to place a 0.47/250V cap.But can I place a 0.1/250 V cap?

here is the picture of what I have.It's a 0.1/250 V cap.

thanks

the value has to be designed for delivering requisite current into the opto 's diode. lower the cap value, less the current , the circuit can deliver( due to higher impedance- you already have a series resistor)try out experimentally as suggested by Ericgibbs.

Sarma
 
Thanks a lot Eric & Sarma I changed the value to 1uF/250V, little bit bigger than the 0.1uF/250V.Anyway its working very well.

Thanks a lot.
 
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