Audio Signal Sensor

[Spoil9]

Long story, but I'm looking to design a super simple audio signal sensor. The idea would be that if there is no audio signal, the output would be a digital 0. If there is any audio signal, then the digital output would be +5V.

I don't have any of my ideas posted to a image hosting website so I can't post the two diagrams I came up with, but one is using a full wave rectifier that connects to a comparator.
The other idea is to connect the audio line directly to an OR gate although now that I think about that I would have to first send it through an amp to get it up to a 5V level to trip the OR gate.

The simpler the better. Speed is not a major concern, but power consumption and size/ price is as I would need to use this on 4 audio lines.

Any tips or suggestions?
Thanks.
- Will

[Soeren]

Hi,

You need to define a level under which you consider it no audio and that level better be above hum and noise on the lines.
Without that level defined, it's difficult to give any useable advice.

Please post your schematics if you really are keen on getting help/comments. It may take a few minutes of your life, but will save us all (you included) several times that, when we don't have to guess and again.
Just claiming: "I don't have any of my ideas posted to a image hosting website so I can't post the two diagrams" don't really give the impression that you yourself have that much interest in your project and that's a bad signal to send, because if you don't care much about your project, then why should we?

[Spoil9]

Fair enough. It was more embarrassment than laziness due to my lack of understanding simple analog electronics but I suppose everyone had to learn at some point or another. I'm uploading them now and will post them in a min.
The audio inputs will be from an MP3 player, GPS and radar detector so I assumed that when there was no audio coming in there would be no noise on the line.

[Spoil9]

Here are my two designs for the audio sensor part. The top one is from a buddy of mine, and the bottom one is mine.

[Spoil9]

Here is the over all circuit layout. The idea is that A0-A3 are audio jacks. The priority encoder picks the signal with "highest" priority and routes that audio to the out put via transistor which is controlled by the decoder.

The reason for this is because I ride a motorcycle and I want to listen to my MP3 player. But I also want to mount a GPS and a radar detector. While I'm riding along I want to listen to my music but when the GPS gives out it's turn by turn I want that audio to take "priority" over the music so the music should cut out and the GPS would cut in.
On top of that, the radar detector should be the highest priority of the three since I do ride a sport bike. 

Once I get something like this to work, I think the next step would be to add some sort of "mute" to an input, or maybe a mute timer as all I need is a sec for the audio from the radar detector to know I need to slow down where as if that goes off when my GPS is talking it could be 3-5 sec before the GPS becomes priority again and in that time I could miss something. However that idea is "down the line" sort to speak as just getting this built and usable is all that is important to me at the moment. I have to many other projects I need to design and build before I start tweaking this one too much.
(remote motion sensor, Halloween decorations, week long cricket feeder, etc)

[Soeren]

Hi,

The idea is that A0-A3 are audio jacks. The priority encoder picks the signal with "highest" priority and routes that audio to the out put via transistor which is controlled by the decoder.

You'd need the logic for the priority encoder separate from the audio routing (controller and controlled shouldn't be the same line).
But... It could be done in more ways than one.

The reason for this is because I ride a motorcycle and I want to listen to my MP3 player. But I also want to mount a GPS and a radar detector. While I'm riding along I want to listen to my music but when the GPS gives out it's turn by turn I want that audio to take "priority" over the music so the music should cut out and the GPS would cut in.

Ahh, so it's safe to say that, if there's not a comfortable loud signal, it should be taken as no signal?
That loosens the specs a bit and makes things less critical if that's the case.

On top of that, the radar detector should be the highest priority of the three since I do ride a sport bike. 

Wouldn't some kind of beep or similar be adequate to tell if you're getting too "sporty" for the immediate situation?

Once I get something like this to work, I think the next step would be to add some sort of "mute" to an input, or maybe a mute timer as all I need is a sec for the audio from the radar detector to know I need to slow down where as if that goes off when my GPS is talking it could be 3-5 sec before the GPS becomes priority again and in that time I could miss something. However that idea is "down the line" sort to speak as just getting this built and usable is all that is important to me at the moment. I have to many other projects I need to design and build before I start tweaking this one too much.
(remote motion sensor, Halloween decorations, week long cricket feeder, etc)

Let me see if I get this:
Normally Nina Hagen is beating your eardrums, but when the GPS has something to say, Nina is told to shut up until the end of the GPS message, whereafter Nina returns, perhaps with a short pause in between, to give your brain 400..800 ms to process the GPS info. No matter whether Nina or the GPS are are crooning, if the Radar detector goes off, it needs to get its say, perhaps just with a short tone or a short slice of the alarm sound - does that sound right?
Can the alarm be set to different messages/sounds?

[Spoil9]

Soeren,
Normally I would agree that the controller inputs should be sepreate from the audio inputs but I am not that educated in this and I did not see anyother way of setting this up. I am open to suggestions though.

Ahh, so it's safe to say that, if there's not a comfortable loud signal, it should be taken as no signal?

For my application, yes, this would be correct.

Wouldn't some kind of beep or similar be adequate to tell if you're getting too "sporty" for the immediate situation?

It would, but the radar detector I have has a different beep for K, Ka, Laser and each beep goes on for 3-5 sec. I am looking at getting a new radar that also alerts me to emergency vehicles approaching and to road construction a head but I don't know how those would differ with the tones or the length of tone.

does that sound right?
Can the alarm be set to different messages/sounds?

Except for the Nina Hagen part, yes. That is exactly how I envisioned this system to work. And with the one I have now, no the tones/ sounds can not be changed.

I am really not too concerned with muting the radar. I think I can live with the 3-5 sec interruption as I may or may not be plugging it into the same jack every time. Although I don't now, I  really don't know if there will be a fourth device plugged in at any time. Or as I ride I may learn that the GPS is more of a priority than the radar.
(especially if I ride with my girlfriend as she looks over my right should and just happens to be right in line with the radar so when it lights up she sees it and taps my helmet which lets me know it's going off with out having to take my eyes off the road)

[Soeren]

Hi,


Here is how I envision it done. Using miniature relays it could be made better though, but I have an idea that you won't like that detection is on the left side on a stereo signal (since that's the one that's hot in a mono jack as well).
Does that cover your needs?

An amplifier at the output side would compensate for any lack of volume, but if you don't use max. volume as it is, it shouldn't be mandatory.


Oh well, nearly forgot the schematic
http://That.Homepage.dk/PDF/Audio-Priority-Selector.pdf

[Spoil9]

Wow, not going to lie. That is quite impressive in it's simplicity. I really like it. My only question would be, why did you choose those transistors? Is there something special about them or will equivalents from jameco.com work?


On a side note, I was reminded of a de-bounce circuit for a 555 timer, and although I guess I don't need a signal sensor anymore, I was wondering if this would have worked?

[Soeren]

Hi,

My only question would be, why did you choose those transistors? Is there something special about them or will equivalents from jameco.com work?

I selected those for being in a TO-92 housing and with the lowest R_ds_on I could find without spending lots of time on it.
Other types will probably be OK. Do you have any particular in mind, then post the type-number (and a link if possible) and I'll take a look at them.

Do you plan to add an amplifier?
(This is important in selecting the resistors).


With miniature relays, you wouldn't need to attenuate the signals and they can be quite small. I'd recommend Reed-relays, although smaller types can be found, as Reeds are easy to find - usually in what looks like a very thick (tall) 16 pin IC.

On a side note, I was reminded of a de-bounce circuit for a 555 timer, and although I guess I don't need a signal sensor anymore, I was wondering if this would have worked?

Without seeing the circuit, I cannot tell.

[Spoil9]

Sorry for the delayed response. Ex-gf drama.

I have no transistors in mind, just wondering the reason behind your choices so that I may learn something more. I have yet to sit down and bread board this so I can't say if I'm going to add an amp or not. I was planning on adding a simple amp for the gps but was going to use an adjustable resister IOT be able to adjust the gain of the amp.

I have no issues with using what works. I can bread board both transistors and mini-relays and see what I like and the benifits of each and go from there.

[clark97]

Thats very interesting, could this be adapted for line level switching. If so what resistor values  would you suggest. Is the sensor circuit sensitive enough to pick up a quiet track at line level?