I KNOW!!! Groovy, huh? I can't wait.

:icon_cool:

BTW, I am pretty sure you will have to use the high going output on the TR-7...the nav. is mute on high, not low like the phone.

Ah! Thanks for the info! I just bought a TR-7. I hope that it can kick in very quickly. I'd hate for the beginning of the audio to get clipped.

Hmmm... Now that I've read the instructions for the TR-7 I'm starting to wonder if it's going to work. Have you used them in this application?

Nope...I had said earlier I had not actually tried it...so do it at your own risk.

The feature 12 timer does have an 'instant on' mode...how instant remains to be seen.

I do have my Garmin GVN-53 hooked up to the nav mute however, and it works fine.

I soldered a jack to the Garmin. I programmed the PAC TR7 for feature 12, instant on, time delayed off. After extensive trial and error and testing, I found a couple of interesting things. First, apparently the " - " speaker out from the garmin must be grounded, otherwise, the PAC TR7 doesn't recognize audio when Garman girl speaks. In addition, the output of the Garmin is barely enough for the PAC TR7 to recognize, and often the latch is delayed, and if the timer is not long enough, the trigger (mute) will be choppy. I think it is possible that this grounding of the speaker negative out might not really be necessary if the output was higher, but I have not yet purchased a Line Driver Signal Booster. I was about to, but started thinking about my set up, and now I have more questions. For instance, one of my interests is to use the Garmin bluetooth phone interface with my blackberry. This works fine, but, if I connect the Garmin to the sterero and if the PAC TR7 sucessfully triggers the phone mute and the Garmin audio is passed through to the car speakers, what happens during quiet times in the phone conversation? I think it will keep cutting out and back in. So then I started thinking about Sam's idea with the T605. Sam would not have the same issue I would have because presumably, the T605 mute line is activated internally when the T605 is on an active phone call. This is now getting complicated. I considered installing the T605 in conjunction, and allowing it's mute line to mute the stereo, but still have the phone call go through the Garmin (essentially, both devices, but not connect the speaker outs from the T605. However, I beleive I would need to press a button on the T605 when a call is coming in, AND select it on the Garmin too (if I can even have two bluetooth devices answer one phone). So, pressing the T605 answer button isn't really an option. I am not sure this all is going to work like I want it to. Maybe I need to just replace the HU with one that has a slide out display that has built in GPS and bluetooth.

I spent half of the day trying to make this work for me. I have a 2.5 vdc bias on the wires coming out of the little Garmin speaker. It was holding the TR-7 on continuously because the TR-7 triggers at 0.8 volts. I first tried to use an RC circuit to filter the DC, but then the Garmin unit didn't have enough power to trigger the TR-7. It only puts out about 0.5 volts peak to peak, and the TR-7 needs 0.8 to activate (DC, presumably). So now I'm off to Radio Shack. I'm going to buy an isolation transformer, a few transistors, and some diodes to make a bridge rectifier. The transformer will eliminate the DC, the transistor will boost my audio AC to a point where it should trigger the TR-7, and the rectifier will turn the higher voltage AC into DC, just in case the TR-7 doesn't trigger with the AC.

I also learned something interesting about the way the volume control works for the nav input on the amp. Apparently the nav volume is a proportion of the radio volume, not a fixed level. I can set it so the nav audio is equal to the radio volume, louder than it, or quieter than it. I don't think I really like that. I like my nav lady to talk to me at the same level every time. Sometimes I'll be listening to music loudly, then I'll be listening to talk radio at a more "normal" level. If I set the nav volume so that the lady doesn't scream at me when listening to music, I bet it's going to be too quiet when I'm listening to talk radio. Oh well... I'll deal with it.

I really admire the dedication that both of you are putting towards solving this!

Steve, I think you are correct that there is no straightforward way to get a 'solid' mute out of the Garmin for a Bluetooth phone call because of long silences possible on calls. Rather than adding a Motorola Bluetooth unit, you could accomplish the mute with a manual switch on the mute line (in addition to the TR-7), and you would flip it sometime after you pick up the call with the Garmin....not ideal, but it is simple and would work. Setting the turn off delay a bit longer, say 3 or 4 seconds may be a good idea also.

I think that the LD-10 preamp will solve your trigger problem. it also has in internal jumper setting to float the ground if needed. It should remove any DC bias and provide more that enough trigger drive, which you can tweak with the level controls to get exactly right.

Sam, the LD-10 preamp is probably ther easiest path for you also. What you propose will work, but is a bit complicated. If you want to homebrew something, another simpler approach you might want to consider is to use a level comparator chip (or an op-amp connected as a comparator). You can have it trigger at levels just over the 2.5v DC bias + noise, say 2.6v or so and it would output a solid level to trigger the TR-7.

One more thought...another advantage of the LD-10 preamp here is that it is a stereo unit, with separate R & L level controls. You can drive both inputs with the Garmin, the tweak the correct level for the LD-10 on one channel and the ideal volume for the audio on the other channel.

Well, I installed the isolation transformer, which obviously eliminated the DC. The Garmin still didn't have enough oomph to trigger the TR-7. So I installed a transistor to boost the power coming out of the transformer. Woohoo! That worked!

But then TWO new problems arose. First, the first syllable or so gets clipped, which is really irritating. I was using feature 6, by the way. Feature 12 doesn't work because it only holds the output on as long as it's receiving an input. The slight pause between words is enough to cause the output to drop out, then the next word gets clipped. Feature 6 was the only one I saw that made sense, and I programmed the TR-7 for a 5 second delay before cutoff. That means as soon as the lady starts talking the TR-7 will mute the radio audio, then turn off the mute 5 seconds later. I figured that was enough time to get everything said. Also, related to this first new problem, when I do the key presses on the touch screen they happen so fast that the TR-7 never picks them up. I don't get the feedback "beep". But sometimes right after the beep the audio mutes (it actually never really "mutes", it just attenuates the music and plays the GPS audio over top of the music).

The second problem is that the Garmin is over driving the amplifier. I need to set it at 70% to 80% volume in order to trigger the TR-7, but at that level the GPS audio coming out of the car speakers is loud and distorted, even when I turn the nav volume all the way down to -3 on the head unit. And before you ask, yes, the amp is being driven directly from the Garmin. It's not going through the transistor first.

To resolve the second problem I can probably just either rig up a Darlington pair to give the TR-7 a bigger boost and then turn the volume on the GPS down to 20% or so. Or I can install a pot to reduce the power going to the amp. The second solution would be easier, but the first solution might lessen the clipping problem. I'll fiddle with it tomorrow. I'm done for this evening. Although, I do have a pot I could go install... Hmmm... With the pot I could crank the Garmin volume up to 100% and see if that reduces the clipping, too.

One other thing I'm thinking about doing. This would actually be the easiest thing of all. The nav "mute" doesn't really mute the audio. It just reduces the volume of the music (or whatever you're listening to). You can still hear it. I figured out that by simply turning up the volume I can still hear it just as well. It didn't appear to reduce the sound quality of what I was listening to. I could simply rig up a switch in the cockpit somewhere that would leave the nav mute active all the time. I'd still hear my music and the Garmin lady would be audible over the music because I could set the volume on it separately. Then, if I ever wanted my music really loud (I'm 45, so it's kinda rare but it happens :) ), I could just switch off the nav mute and have the radio at full volume to blast Justin Beaver as I picked my daughter up at school. In fact, 90% of the time I don't even use the GPS, so 90% of the time the nav mute switch would remain in the off position. I'd only turn it on when I'm using the GPS. That would totally eliminate the clipping problem, and even the button presses would be heard through the car speakers.

That's what I'm going to do. After meditating about it, I've realized that I will probably never eliminate the clipping problem so this will be the best solution. Now, where am I going to mount the switch? It's just going to be a little latching push button. I so wish I had a second set of wood pieces. All of that real estate, yet I don't want to use any of it.

Man, I am bummed that feature 12 works that way:icon_doh:

Well, if the increased signal level cuts the clipping, you might be OK for the nav., most of the time anyway with feature 6.

Looks like a custom trigger/delay circuit is the only way to do this perfectly.

Sounds like a good, simple solution for you. That little vent next to Valet switch is a dummy...you could mount a switch there.

DONE!!! Well, sorta. I still need to install the switch which I'll get later today. And after buttoning everything up I developed a little hum when the nav mute is activated. I have a shorted shield somewhere I need to find. The door lock to fuel pump relay timer works, and the Garmin audio is now playing through the car speakers! Woohoo!

Got this all done earlier today. Rather than trying to get make something try to instantly activate to attenuate the stereo, I just rigged it so that if I'm using the GPS I can flip a switch to have the Garmin audio play through the car speakers over top of the music. It works great. Sorry about the run-on sentence.

So now, with the Motorola T605 installed I can play my tunes directly to the stereo without having to plug anything in. When the phone rings it automatically mutes the stereo and allows me to talk hands-free. And the Garmin GPS talks to me through the car speakers. Life is good! I also got my fuel pump primer working, but I'll talk about that in the other thread! AND... I fixed another issue, too! But I'll talk about that in the other thread, too. I'm very happy now.

Sam, glad you have yours all working the way you want. I am in a holding pattern for now though. As I mentioned before, I am not sure this all will work the way I had hoped, particularly for the bluetooth phone calls through the garmin. As Steve (whiteXKR) mentioned, I could rig a switch to flip when on a phone call, but I am still considering just replacing the radio altogether with something that has an LCD screen, NAV, and bluetooth built in. Part of the motivation for that is because my factory radio sometimes wont turn on without pressing the power button 10 to 20 times. I do think the button is bad and not the rest of the radio, because if I leave the it on when I turn off and pull the ignition key, when I turn on the car again later, the radio comes right up, no issues. Anyhow, what concerns me about installing a replacement radio is all of the concerns everyone else has had, such as the trim plate, wiring (do I use the factory amp - I would like to I think), etc. So, I am looking around and researching.

The Garmin audio would not reliably trigger the PAC TR7, so most of the time the TR7 would not latch the mute line. I finally installed the PAC LD-10 to amplify the Garmin audio. Now, the PAC TR7 triggers the phone mute more reliably, however, still not good enough. Somtimes it takes a word or two of Garmin speaking before the mute is triggered, and sometimes when Garmin talks for a relatively long time, the trigger times out and the mute signal turns off, then it triggers again, which results in choppy audio. If I set the latch time longer, it helps with this, but, it leaves the mute on too long after Garmin finishes. I just think this is not going to be a reliable option for me.

Is there anyone else interested in swapping in a portable Garmin this way and using the car's mute? I can easily design and build a simple circuit that would work reliably and get a Printed Circuit board made...but I need at least a few takers. It would be in the $50 neighborhood in very low quantities.

I just came across this little kit that may well do the job:

http://www.electronics123.com/s.nl/it.A/id.361/.f

I think the biggest hurdle might be difficult to overcome. Even if the voice activated relay could instantly trigger the amp, I think there is a little delay in the amp itself that will always cause the first syllable or so to get clipped.

Having said that, I'm going to buy one of those kits you linked to above, just to try it out. I'll let you know the outcome.