Audio Relay Swtich

[Fudge_Brownie]

I asked this question a little while back, well something along the lines of it. Now I think I've got something much more specific that someone with a little audio/electrical experience might be able to answer.

I want to play the radio, with a 2nd audio source (in this case, police scanner), that when audio comes from source 2, it plays INSTEAD of the music. Sorta like at Wal-Mart when they have music playing and they talk into the Mic, it stops all music for the time they are speaking.

I would assume in the wiring harness, theres 8 wires for each of the 8 speakers within the car, though this seems like a little detail I need to work out. Assuming this is the case, I'd need to cut each of those wires, and tie them to a relay of some sort that would switch to source2 when ever a signal was found.

I've included this craptastic attempt to depict the issue.

[PyROZen]

yeah this could work, but i'd probably recommend switching sources via a switch instead of making it signal sensing. Not sure where you would find a relay with 8 stages of I/O but i'll bet someone makes one.

[CAPT_BLOTTO]

first of all there is 8 wires but they're in pairs + and - for the front left and right and rear left and right.

As far as signal sensing thats going to be a little tricky. Maybe if when the scanner picks up something its puts out 12v then it could be used as a switch but doing something like this doesn't seem feasible then you have the problem of volume levels. Would the police scanner have enough power output so that you can hear the speakers or would the relay have to be an amplifier as well?

[Fudge_Brownie]

I thought about the audio issue and I'd probably hafta get some sorta low end in-line amplifier to put on the scanner's audio-out.

The 8 I/O relay could be replaced with several 2 or 4 I/O relays and wire the scanner's audio into each of them instead right?

Basically what I need is a relay that switches based on when there is a signal.

[BEJinFBK]

I thought about the audio issue and I'd probably hafta get some sorta low end in-line amplifier to put on the scanner's audio-out.

The 8 I/O relay could be replaced with several 2 or 4 I/O relays and wire the scanner's audio into each of them instead right?

Basically what I need is a relay that switches based on when there is a signal.

Instead of mucking about with the system, why not hang a speaker up high,

near your head connected to the scanner? The center roof console would work.

Leave the stereo alone.

With the setup that you're talking about, you would get tired of it in short order,

and NO one will want to cruise with you. You'll propbably also have some nasty

switching noise...

If HAVE to do this, You might consider just working with the Front Left...

[Fudge_Brownie]

Cause im a gadget junkie (why do you think I have a scanner in the first place? ), I over think things, and I wanna be able to crank the music but still listen to the scanner.

I've considered doing a separate speaker mount, but I hate the ugly look it's gonna give. I'm thinking about on the B-pillar behind my left ear, so I'll hear it and won't hafta look at it. This is plan B.

No one will ride with me? Ya I know that, and that's why I'd be turning the scanner off during cruises with friends. Heck, sometimes the thing's all static and even I don't wanna listen to it. But for stuff like drives between school and home, it'd be nice to have hooked up so I can do music and listen to the scanner at the same time. When you're driving, and theres radio silence... you put on the music, to have some chatter pop on, and you find yourself fumbling for the stereo controls, and reaching for the scanner. It breaks down to listening to music or listening to nothing with the occasional talk on the scanner. Thats why I wanna rig up both.

I was talking with my little brother last night and while it appears I'll need relays, I found out I had quite the misunderstanding of the relay.

I thought the line that controlled the switch, once switched on, was then routed to the "output" of the relay. This is not the case. So now I need some sort of switch device that I don't even know the name of. Any ideas?

[b3atboxjr]

police scanner, as in, something that picks up on when cops talk to base or vice versa, yes?

my thinking is that any scanner will be attempting to recieve and reproduce transmissions at all times, and it doesn't function like: when it picks something up it suddenly turns on.

this being the case, you would have no changing electrical signal to activate a relay.

your only option is to dedicate a speaker (added or stock) to the scanner.

[Fudge_Brownie]

Crapppppp you're probably right that it would still have some sort of null signal right?

Yes you are right about the device, though technically its a "radio scanner" because it can listen to all frequencies between 0-800mhz, just gotta learn what frequency the local cops are on.

The switch would hafta be voltage-sensitive I guess, since when someone spoke, the voltage would be higher in order to move the speaker?

Could try stealing the driver's side tweeter, and having a physical switch to turn it back onto the stereo when not using the scanner. Also, since the scanner reproduces a somewhat muddy and deep sound making the voices blend together, the tweeter might help to clarify.

[b3atboxjr]

does the device have it's own speaker? or does it just have audio outs, like, RCAs or something?

but yes, probably either way (speaker or audio out), you'll need some sort of device that activates after reaching some sort of AC voltage threshold. like uh, clappers (clap on, clap off) use something like that, except that it prob just monitors dB levels (cutoff with a capacitor) which isn't the same thing.

so good luck finding this mystery device! or you could just dedicate a coaxial speaker to it... (the easy way! sheesh)

[BEJinFBK]

Ok- I get the gadget freak thing...

What I'd look for is a scanner that provides a

12 volt signal out when it breaks squelch.

Use that signal to trigger the relay.

If you just go with the FL channel, all you are

gonna need is a DPDT relay that will

connect the two wires between the stereo and

the FL speaker when "at rest", then connect

the speaker to the scanner output when the

signal from the scanner tells it to.

Plan B = just mount a DPDT switch in the dash

and do it by hand when you wanna scan.

DPDT = double pole, double throw

or

6 contacts. (+ 2 for the relay coil)

[b3atboxjr]

yes, that would work.

perhaps find a scanner with LEDs that light up when it gets a strong signal. then you could tag one of those LED legs.

or just install a switch w/a relay, s'all good.

or maybe instead of installing a switch, just have the relay activate when you turn the scanner on. (unless it's more convienient to have it on all the time, then you can do a switch in the dash).

[BEJinFBK]

What would REALLY be cool is an S70 with Dolby Surround.

Just tag into the center dash speaker! Excellent... B)

[drlava]

Here's a craptastic mspaint schematic of a circuit to do what you want. Input is line level from your scan ner. R1 is sensitivity adjustment. There will be a turn-off delay before it switches back, in case of Rogers. R4 is turn-off delay adjustment. Squelch should be activated for best operation.

WHAT!? no attachments on this board? hmmmmm

[bottlecap]

taking the activation signal off a metered led is a clever idea.

i think using a bunch of normal relays would be the best way to go, rather then shelling out crazy cash for some rare relay. just daisy chain them and use the same signal to trigger them all. that way one circuit triggers all of the audio paths just as you'd like.

as for using an audio signal as the trigger... uh... i dunno how well that'd work out for you. i suppose you could find a noise gate and adjust it correctly. that way only stong signals would make it through the gate and that might be workable. the thing about using the audio signal is that you would need to split it into a trigger source and the audio source. that isn't really that hard but there's got to be a more ideal way.

i'd also learn that scanner inside and out. there may be something on the board that performs a similar function that you could tap into. something like the led idea.

EDIT: sorry i've had this page loaded for a long time (a week +) and missed the above reply. that seems like your best bet. kudos to the dr for knowledge of things electric.

-mike

[BEJinFBK]

Maybe someone has a voice operated relay for a telephone recorder

or dictation equipment that you could find off the shelf.

I think Radio Shack used to sell one, but it might have been triggered

by Off Hook voltage drop, not audio. I'm not sure.

I still like the idea of giving this thing it's own speaker.

Just the whole "less is more", KISS concept.

Less there is, the less there is to break...

If building the circuit above is more than you wanna deal with,

Try searching VOX (voice operated switch).

Hopefully you'll find something out there.

The Ham Radio guys probably have a kit.

Or some of the DIY electronics kits from somebody like this:

http://www.gatewayelex.com/kits4_F.htm

You'll probably have to pad the input, but it should be doable.