phone integration and CD changer control question - SRT Forums

pitviper33 · 09-03-2009, 11:00 AM

Hi all. I've been slowly working on getting my phone to play music in the car, and I'm almost done. I just have one more question.

First, here's what I've got so far. There's a mount just to the left of my boost gauge that holds the phone. It's just within reach of my finger with my hand on the wheel for easy GPS manipulation. But it's still far enough away that I don't have to worry about hitting it during quick hand motion around the wheel. It's right in my field of view, but it isn't high enough to block view of anything other than the windshield wiper. It also happens to be in a great spot if I ever decided to take some in-car video at a race or something. When I slide the phone into its dock, it gets plugged in to a cable that runs inside the dash down behind the head unit. That cable carries charge up and music down. I built a circuit that switches between the CD changer and the phone as inputs for the head unit. When I switch the head unit to that input, the CD changer plays like normal. Unless the circuit sees an audio signal from the phone, then it cuts off the CD changer audio and instead feeds the phone audio to the head unit. If I turn off the phone's music, it starts playing the CD changer music again.

It all works and sounds great, but there's one big annoyance left. While I'm listening to music from the phone, the CD changer is still playing. The sound isn't going anywhere, but it's still reading the disc. So whenever I switch back to listening to a CD, it's on a different song than when I left it. Whenever it plays to the end of a CD, it switches CDs just like it would normally. As you know, this is a pretty noisy and annoying process. To make matters worse, the head unit sees that it's changing CDs and cuts out the audio for a few seconds. I guess the CD changer would be sending some weird sounds during that time, so it just cuts them out. So here I am, listening to phone music, when all of a sudden it goes silent. Then I hear all these mechanical noises coming from the CD changer for a few seconds, then the music comes back in. It's bothersome, and it's keeps the job from seeming really professional.

So here's my question. How do I make the CD changer stop playing when I'm not listening to it? I assume that if I cut power to it, the head unit will refuse to select that input. That's what happens when the changer is unplugged. How do the auxiliary input kits do it? They somehow trick the head unit into thinking there's a changer plugged in, right? If I could do that, I could cut power to the changer and still select that input. Somebody help!

nineball · 09-03-2009, 03:58 PM

i can see how that would be annoying. i have a similar problem with my setup. if i leave my iphone plugged in but turn the car off (like getting gas) when i turn it back on it will work until the bt in the hu connects with the phone. since the latest iphone os now contains streaming stereo bt it screws up once connected. i have to remove the iphone, wait a few secs and reconnect it.

as far as your question, i don't really know of a way to solve it. i can tell you that the aux-in you spoke of requires an adapter that has the same plug as the cd changer cable. the downside is that you cannot connect the adapter and the cd changer at the same time. here is a link to one:

CHRY02-AUX 02-07 Chrysler Auxiliary Input Converter | Visual Efex LLC

pitviper33 · 09-03-2009, 04:19 PM

Yeah nineball, you're never quite satisfied when there are bugs in the system. I feel your pain. Once they finally got with the times and implemented stereo bluetooth on this phone, I definitely wondered if I should abandon my project and go that route. Then all my dock would have to do is charge. Your experiences make me glad I didn't do that. I can work through circuitry issues, but I'm totally clueless for fixing bluetooth connection issues. How's the sound quality over bluetooth?

The kit you linked to is exactly what I'm talking about. Somehow the device in that kit convinces the head unit that a CD changer is connected. How does it do it? My suspicion is that there's some digital communication between the two. That would explain why the kit is so expensive. I'm sure I could buy it and integrate it into my circuit, but I'd really rather not spend so much money. I'm still hoping for an analog way to kill the changer without the head unit knowing...

pitviper33 · 09-04-2009, 07:45 AM

Just a quick update for anybody following this thread (if there is anyone). I did a little more playing last night trying to understand the communication between the changer and the head unit. I can turn on the system and switch to the changer input while playing music with my phone. The system plays music from my phone. Then while it's playing I unplug the harness from the changer. A few seconds later the head unit kicks me out of that input and starts playing its internal CD. So whatever check the head unit is doing for the presence of a changer, it doesn't only do it when you switch to the changer input. It's constantly running the check. The question that remains is how this communication is happening. It's possible that the head unit is looking for a current draw from the changer. It could also be that there's some repeated digital signal from the changer to remind the head unit that it's present.

The problem with more experimentation is that I have to cut more wires. The harness is shielded, and the wires are pretty hard to work with. Here's my newest thought. I know these changers aren't the most reliable pieces. Does anybody have a changer that quit on them and doesn't need his or her harness anymore? If I had a spare harness to work with, it'd be a lot less intimidating to keep trying things. My hope is that in the end I'll have a solution to share with everyone that wants auxillary inputs without giving up the CD changer. I'm most of the way there now.

nineball · 09-04-2009, 02:41 PM

i think you misunderstood what i wrote, or i wrote it wrong. there are zero problems with the streaming bt and the sq is just as good as the hardwired connection. the only downside is that i cannot controlthe iphone via the radio when i am streaming. the problem is that my new hu gives bt priority over hardwired connections. the easy solution is to wait the 15 seconds until the hu pairs with the phone and d/l's the appropriate files (phonebook, etc) then connect the wire. if the wire is connected first, like when getting gas, once the bt is established i have to unplug the cord and then plug it right back in. at that point everything is back to normal. before the os upgrade i did not have this problem due to the old bt.

there would be no integration needed other than keeping your existing power connection. it is basically a fancy passthrough aux-in adapter. i have no idea how it convinces the radio it is a changer but i am willing to bet you will figure it out before too long. on the other hand for around that price you could buy a new hu that has all the features you want built in.

hit up a few local junkyards and look for the parts you need. should be less than $10 for it.