Automatic muting tv when phone rings (help)

[Ronald_ng]

Hello everyone, i have to build a device to mute the tv when phone rings for my final year project in University. I plan to do reverse engineering on the tv remote control so that i can make use of the chip inside it. however, i cant understand the flow of the circuit and the function of the microchip. Anyone can suggest any idea so that i can link the ring detector with the muting system in tv remote control? Thank you.

 

[Gayan Soyza]

Just an idea.

I'd write a protocol to the specific TV (Mute function) & when it hears the ring it will send the IR data packet to the TV by the micro controller.

The phone ring detecting part I'd simply detect by the same micro controller when it hears number of rings it will generate an interrupt in the micro controller & sending the data packet to the TV.

This is the method I do.

 

[crutschow]

If allowed in your project you could just wire into the mute button on a universal remote. The phone ring detect circuit could momentarily close a transistor switch across the mute button contacts to activate the mute function.

Since most mute functions are alternate action, you likely will have to put a one-shot with a several second delay inhibit in the ring detect so it only puts out one mute signal pulse. Each ring would reset the delay. You don't want subsequent rings to turn the TV back on.

 

[kchriste]

Since most mute functions are alternate action, you likely will have to put a one-shot.......

Yes, that would be bad. 1 ring mutes the TV, 2 rings unmutes it, 3 mutes it, etc.
I think Gayan Soyza's idea is better than hacking a remote. This is a final year University project and even using a micro with your own code is kind of lame and won't be too impressive. Now a better project would decode the caller ID string and mute the TV if it was your girlfriend, turn up the volume if it is a telephone solicitor or change the channel from the home and garden network to the PlayBoy channel if it is a buddy calling.

 

[crust]

I have no idea what phone systems around the world are like, nor OPs location. But in the US, the line voltage is at 48VDC when nothing is going on and then when the phone rings or is active the line drops to 10VDC, so it is easy to figure out what is going on. (The ring suprimposes an AC ring voltage on the line).

 

[crutschow]

But in the US, the line voltage is at 48VDC when nothing is going on and then when the phone rings or is active the line drops to 10VDC, so it is easy to figure out what is going on. (The ring suprimposes an AC ring voltage on the line).

The line voltage doesn't drop to 10V until the phone is answered. The ring is a nominal 75VAC at 20Hz and that is what you should detect if you want to mute on the ring signal.

 

[Papabravo]

Hello everyone, i have to build a device to mute the tv when phone rings for my final year project in University. I plan to do reverse engineering on the tv remote control so that i can make use of the chip inside it. however, i cant understand the flow of the circuit and the function of the microchip. Anyone can suggest any idea so that i can link the ring detector with the muting system in tv remote control? Thank you.

I'd be fallin' off my chair shocked if you could actually reverse engineer a TV remote. In all probability it is a non-standard, house branded, 4-bit, mask programmed microcontroller with an undocumented instruction set and non-existent development tools. Good luck with that one.

IMHO it will be far easier to build a stand alone device that replicates the function of the existing remote. While you are at it you might want to build a "TV remote" decoding tool. Point the remote, press a button, send the IR data out a serial port to your PC running HyperTerminal of some equivalent program.

Take a look at the Temic TFMS5380 and friends for some IR sensors.

 

[mramos1]

Here in the US, when I worked for a PABX company it was 90V RMS at 20Hz. You "will" feel every pulse at 20Hz. crutschow is right pretty much.

I am sure there are ring detectors all over the internet. Far as hacking up the remote. If they allow that, go for it. Just need to debounce all the extra rings

 

[alex4421]

i would buy a cheep universal tv contoler and use a transistor that is activated , when the buzzer rings en switches on the mute button , or if it's an older tv maybe you could put a relay between the speakers ?