Modify the phone protector - OPTOCOUPLER

[CyberAle]

Hi all...

I have the circuit of figure 1. The work fine... When I hooking off de phone, one led is turn on.

Well... Now, I try to modify this circuit, like figure 2. I want put an Optocoupler (I try with 817) and connect TX with RX of PC's serial.

The idea is: when hook off the phone, the optocoupler "close" and connect the PC's serial, but do not work...

Does Anyone have any idea?

Thanks!

 

[Nigel Goodwin]

For a start you have the LED in the opto-coupler connected the opposite way to the LED in the previous diagram. You should use a bridge rectifier to feed the opto-coupler, to make it independent of line polarity.

Secondly, the output of the opto-coupler doesn't look to be doing anything very much, you would normally need a pull-up resistor and an HT supply.

 

[Sebi]

Both circuit wrong. Parallel the 7uF! condenser with line kill the ringing signal, and the speech also wrong. Cross connected LEDs cannot work, 100 ohm serial resistor too big.
Use opto with FET-switch output, the LED-side with antiparallel diode and parallel 470nF condenser (seriel with line) will work.
If You apply a bridge - as Nigel suggested - no need the the polarity marking.

 

[CyberAle]

Thank both...

The circuit is a comercial protector of line phone... And this work... If is wrong, I do not now...I am only trying use of opto...

I will try make the Sebi's sugestion... Do you have a code of opto with FET-switch?

Thanks again!

 

[Sebi]

Here is...

 

[CyberAle]

Sebi,

I made the circuit you passed to me, but I used a LED to test only... The circuit work fine!! Thank you!

Now, I have a big problem... In my country (Brazil) I am not finding the H11F1, F2 or F3... No body has...

Do you know anyone other to make the same job? Can I use a relay or a reed switch with an "electromagnetic field" (figure attach)?

Thanks again!

 

[Sebi]

Yes, the relay also work fine, if can pull with about 10mA. Don't forget the parallel 470nF...1uF capacitor.

 

[CyberAle]

Sebi,

Thank you so much! You save my life!

I found the H11F1 and the circuit work fine!!!

 

[CyberAle]

Sebi,

It is me again...Sorry!

I have a small problem: when the phone ringing, the opto is switching... I do not want it...

Do you have any suggestion?

PS: I am using a bridge diode... In this case, Will I need of the diode in parallel of the condenser?

Thank you!

 

[Sebi]

No, but always need the capacitor, it is almost shortcut for AC. The ringing signal is 100V 16Hz, off-hook state about 12V.
If not helped, You need an additional circuit to detecting the ringing signal. With this signal possible disabling the off-hook detector. Maybe need also some delay for output.

 

[CyberAle]

Sebi,

OK...But, I don't know make that... Can you help me?

Thank you!

 

[Sebi]

I never tried it, but probably work...
The PC817 will respond only AC signal, and discharge the delay cap when ringing.

 

[CyberAle]

Sebi,

Your idea isn't work... But is ok...

Thank you!