[rembrant]

I have recently been enlisted by my father to build a switching device for his motorcycle communications. He wishes to have such a device that will switch inputs from his MP3 player to his radio communication when he receives communication over his radio.

I have a few ideas about how this should work. However, I'm looking for some suggestions about what types of components I should use. Indeed this solution should be small and have minimal if no impact on sound quality.

I'm basically stuck. I have limited knowledge of this type of switching and I can't help but think that any device I come up with will not switch fast enough.

All Ideas are welcome.

 

[linuxworks]

sounds like a 'vox' circuit (see 'ham radio').

you have a few inputs and you need to convert the ac signal to some 'sticky' dc switchable signal. then you have all those input signals that need to be priority selected (in case there are multiple 'hits' on the input lines). ie, if 2 inputs have audio active on them at the same time.

in your case, it sounds like the walkie-talkie thing would always take prio, so that would 'interrupt' the mp3 player, always, no exceptions, right?

 

[MASantos]

My car bluetooth gizmo mutes the radio/cdp when I receive a call.

there should be some sort of audio signal auto sensing IC in the market, maybe if you search in TI's, national and other IC companies for this. Most of them have easy to use search functions.

Google is your friend too!

Manuel

 

[rembrant]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif sounds like a 'vox' circuit (see 'ham radio'). you have a few inputs and you need to convert the ac signal to some 'sticky' dc switchable signal. then you have all those input signals that need to be priority selected (in case there are multiple 'hits' on the input lines). ie, if 2 inputs have audio active on them at the same time. in your case, it sounds like the walkie-talkie thing would always take prio, so that would 'interrupt' the mp3 player, always, no exceptions, right?

Yes, that is exactly what I am looking for. The radio communication should always interrupt the MP3 player.

 

[linuxworks]

Quote:

Originally Posted by rembrant /img/forum/go_quote.gif Yes, that is exactly what I am looking for. The radio communication should always interrupt the MP3 player.

heh. I had to do that exact same circuit for my car gps

the stereo plays normally but when that stoopid lady inside my gps wants to yak at me, somehow the relay in my vox circuit gives her the nod and my stereo mutes and she has her annoying say

after she stops and things get quiet, the relay clicks again and the smooth sound of music again fills the car interior.

that what you're looking for, more or less?

 

[rembrant]

That is exactly what I'm looking for linux. There are several diagrams available.
1 Does the circuit you describe ever switch late?
2 Does it ever cut off in pauses between words or sentences?

I will basically be building a switch with two inputs. The MP3 input will be on a normally closed relay that should open when voice is sensed on the communication line. The radio input would be on a normally open relay that will close at the same time.

What type of relay is generally recommended for such an operation? I would like to avoid using five separate relays for this project. (3 NC for the stereo MP3 and 2 NO for the mono radio coms) Needless to say, a flip flop with multiple switches would be ideal.

Before anyone gets smart and lets me know that there is a led on most radios that comes on when they are receiving coms... Yes I know. However, that would require me to hack every radio my father intends to use. Thus, it is out of the question. I want him to be able to use any radio he wishes without having to ship the thing to me for surgery.

 

[error401]

Probably easiest to use two DPDT relays. Use opposite sides of each and you're done. Grab any of the simple vox circuits from the web, most of them are pretty simple - basically a simple common-emitter amp, an opamp as a comparator and a time constant will do the job. Add your relays a driver and some protection diodes and you're done.

TQ2 relays would work well for this, and they're pretty cheap.

 

[rembrant]

Hmm, this seems like the most simple schematic I could find. I have most of the parts for this one already.

Looks like the whole circuit is isolated from the relay already and the lm386 should provide the required amperage.

What do you guys think? I am slightly confused as to what A.in and out means as well as why there is a capacitor between them. Seems like it serves no useful purpose.

 

[error401]

I was thinking something more along the lines of this: Basic Vox Circuit

Using LM386 for this seems a bit strange to me, though I guess it keeps the parts count low. A out seems to be an output for use with certain transceivers, maybe it automatically keys the radio or something? Not sure.

 

[rembrant]

Yea I have that schematic saved as well. That one requires a dual opamp(one that I don't have at that) plus a transistor. Unfortunately, the LM386 scheme comes with no clear instructions. For instance, the 1000MF cap is labeled as hang time. I'm not really sure sure what that means. Also I would assume that the resistor to ground in between the cap and the diode would be where to adjust the time on for the circuit.(labeled as 10-20-Ohm)

This is just gonna be one of those build it and see type projects I guess.