What is the Capacitor value to put here? - Electronic Circuits Projects Diagrams Free

Suraj143 · 10th August 2007, 05:17 AM

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

mvs sarma · 10th August 2007, 05:54 AM

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

Suraj143 · 10th August 2007, 06:19 AM

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

ericgibbs · 10th August 2007, 07:39 AM

Quote:

Originally Posted by Suraj143

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

mvs sarma · 10th August 2007, 02:15 PM

Quote:

Originally Posted by Suraj143

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

Suraj143 · 12th August 2007, 05:09 PM

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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10th August 2007, 05:54 AM	(permalink)
mvs sarma	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

12th August 2007, 05:09 PM	(permalink)
Suraj143	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.