Need vox to reset ne555 on no sound help

[nickcol]

Hi

I have an IP phone which I need to connect to a LOUD ringing bell.

I have used a ne555 timer chip and a driver transistor to ring the bell which works well. Ie when power applied the bell rings contiunesly.

But I need to now connect it to the IP phone.

The connection I can get on the phone is to the 2 wires on the small 8ohm internal speaker inside it which is only used when it rings and speakerdial.
(we wont use speaker dial).

I was hoping on feeding the 2 wires from the speaker into a small transistor switch which would light a led in an opto isolator and pull the ne555 reset line high only when sound rings ie ring silence ring silence the ne555 would run only when the phone actually rings.

Any simple ideas ?

Thanks

Nick Colyer

 

[audioguru]

Hi Nick,
You didn't attach a schematic of how you will connect the opto-coupler to the reset and supply pins of the 555, and we can't see if you have a resistor to ground on the reset pin to turn off the 555.
We also can't see how you have rectified and filtered the ringing tone from the phone's speaker.

 

[nickcol]

Hi

Sorry about the lack of info on my previous post, I have the following ne555 circuit working to ring the bell when the reset line is pulled High.

What im after is some idea on how I can connect somthing to the speaker wires on the voip phone and then to a pnp transistor on the ne555 reset line to +ve. so that when the speaker has sound on it the ne555 will turned on and when the speaker has no sound the ne555 reset would be held low.

The sound would be Ring-------Ring------Ring. The ne555 needs to run during each ringing sound.

Would using a lm386 opamp chip to amplify the speaker sound and then on the output of the lm386 use a combination of resistors and a large capacitor to make the output stay on for longer.
This could then turn on a pnp transistor between the reset line and 12volts.

Is this the best way to try it or are there other ways to do this.


Thanks

Nick

 

[audioguru]

Instead of posting your big huge sketch as a fuzzy JPG file type (used for photographs) on another website, why not reduce its size, save it as a clear GIF or PNG file type and attach it here on this website?
I reduced its size but it is still fuzzy because it was originally a fuzzy JPG file type and here it is:

 

[nickcol]

I have redone the circuit I have used so far so is better quality. Sorry but I did not read the faq first.

Its quite basic timer which just goes on/off several times a second and drives a transistor which drives a solinoid to ring the large metal bt bell. The ne555 will only ring the bell when the ne555 reset line is pulled high as its by default pulled low by the resistor to gnd. This works great.

Sorry but I dont have the values of the resistors or caps as the circuit is at work and im off for a while.

What im looking for is some circuit to attach to the voip phone internal 8ohm speaker which only sounds with the phone rings and the ne555 reset line. The idea is the ne555 reset line would be made 12volts only when sound is heard through the speaker.

I had thought about trying the attached circuit from the led music pulses topic. I Could increasing the 220uf cap to somthing larger make the led stay on constant when the phone rings and off between the ringing sound. If this would work i should be able to connect it to a pnp transistor or opto coupler between the ne555 reset and 12 volts ?

Does this sound possible.

Thanks
Nick

 

[audioguru]

You don't need another amplifier.
The phone's speaker amplifier should be able to drive the LED in the opto-isolator through a coupling capacitor in series with a current-limiting resistor, then the output transistor in the opto-isolator could drive a PNP transistor through a voltage divider to its base. A capacitor could filter audio from the reset wire.