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Crazy IPod charger idea, need help.

post #1 of 21
Thread Starter 
Hi guys,

I have a TREAD running off a 24V wallwart which outputs around 22VDC Regulated. I also have an IPod Video. Naturally, I want to charge the Ipod off the TREAD. As far as I know, IPods are rated at 8-30VDC through their firewire ports.

My idea is to solder a 2.1mm DC power jack into an IPod dock connector.

Judging by the IPod pinout, this is what it should look like:

Pin - Connection
19 - Ground
20 - Ground
29 - Positive Lead
30 - Positive Lead

I also know that pins 11 and 21 are used for ground and signal respectively of "Accessory Detect" and if they are not used then the IPod's internal voltage regulator is bypassed. This is my main concern. I know my TREAD will provide stable regulated voltage well within specs of the ipod, but should I be bypassing the internal regulator or not?

Adding the following will act as an "Accessory"
Pin - Connection
11 - Ground
21 - 1M Ohm resistor running to 29/30

Like I said before, making this an accessory uses IPod's internal power regulator, leaving it out skips the regulator.

If I'm providing around 22VDC to the IPod, what do you think? Skip the regulator or not? Not sure how many people have tried this but I'm a little afraid to fry my IPod in the process of experimenting.

Any help / advice / knowledge you can add to this thread is greatly appreciated.

Thanks in advance.
post #2 of 21
Dup.
post #3 of 21
There is a thread here discussing this issue. Last I saw, people were having trouble getting it to work, and someone came up with a solution, i think. IOW, that thread is just what you need.

If I can find it in my favorites, I will post it. Try the search. "ipod pinout" will get you going.
post #4 of 21
Yeah I had that crazy thought too the other day when looking at my Millet. What if you can put the amp with STEPS or TREAD all in one with a built-in ipod dock so that it charges and connects to the line-out. Hope someone pulls it off in the near future.
post #5 of 21
Quote:
Originally Posted by dmunky
Yeah I had that crazy thought too the other day when looking at my Millet. What if you can put the amp with STEPS or TREAD all in one with a built-in ipod dock so that it charges and connects to the line-out. Hope someone pulls it off in the near future.

For awhile I worked on a design for a Pimeta in a Hammond with a dock set into the top of the case. I think it could be done but it takes a long wide no fly zone running down the middle of the case. This was also going to be battery powered with AA or AAA and I couldn't afford the space. Then I gave it up after I decided to build a PPA instead.

It's an interesting idea, though.
post #6 of 21
Maybe this can be of some help:

http://www.engadget.com/2006/04/18/h...r-dock-part-1/

Shows how to make your own ipod connector with diagrams of all the pin-outs to utilize all the features.
post #7 of 21
Thread Starter 
post #8 of 21
Thread Starter 
Cumulative PinOut (A bit of info from everywhere)

1 Ground (-)
2 Line Out - Common Ground (-) (Connected to Pin1)
3 Line Out - R (+)
4 Line Out - L (+)
5 Line In - R (+)
6 Line In - L (+)
7
8 Video Out - Composite Video
9 S-Video Chrominance
10 S-Video Luminance
11 Accessory Detect Ground (Use for Accessory Detect resistor to work)
12 Serial TxD
13 Serial RxD
14
15 Ground (-)
16 USB GND (-) (Connected to Pin15)
17
18 3.3V Power (+) OUTPUT
19 Firewire Power 12 VDC (+) 3
20 Firewire Power 12 VDC (+) 3
21 Accessory Indicator - (Some resistor values are at http://ipodlinux.org/Dock_Connector)
22 FireWire Data TPA (-)
23 USB Power 5 VDC (+) 9
24 FireWire Data TPA (+)
25 USB Data (-) 9
26 FireWire Data TPB (-)
27 USB Data (+) 9
28 FireWire Data TPB (+)
29 FireWire Ground (-) 5
30 FireWire Ground (-) 5
post #9 of 21
Just out of curiosity, how does the iPod determine if the line out is controlled by the volume control? On a sendstation, for example, it is not, but with Apple's Univeral Dock it is controlled by the iPod's volume control. Is this some resistor value on the accessory indicator pin?
post #10 of 21
Thread Starter 
Yes, it is the accessory detect resistor that tells the IPod what is connected to it.

I think using 1M is the best choice as it pauses the Ipod when disconnecting LineOut and turns off the IPod when power is cut. Since the "power cut" only happens when you're charging it, it shouldn't be a big problem.

But of course there is the whole thing about the internal voltage regulator that you have to consider, if using accessory detect, it's on, if not using accessory detect, it's off. Really gotta figure out which one is safer to do at high voltages.
post #11 of 21
Quote:
Originally Posted by NeilR
Just out of curiosity, how does the iPod determine if the line out is controlled by the volume control? On a sendstation, for example, it is not, but with Apple's Univeral Dock it is controlled by the iPod's volume control. Is this some resistor value on the accessory indicator pin?
The iPod itself does not have any volume control of the Line Out signal in the dock connector. It is the Universal Dock that have the possibility to attenuate the the signal and it can receive commands from the iPod to do it.
post #12 of 21
Thread Starter 
I got 2 questions for you guys that have built an IPod connector with FireWire.

1) Did you use Accessory Detect and if so, what Resistor did you use?
2) Did you ever try running more than the regular 12V through it?
post #13 of 21
Nice idea!

A while ago I tried to power my Ipod 4G from the TREAD that supplies my Pimeta.

I had to give that idea up, though, because the Ipod ties audio GND to the other GNDs (USB, FW) internally.
This effectively caused a short between V- (=Firewire GND)
and audio GND, collapsing the amp's virtual ground.
I thought about using only V+ and virtual ground (bufferd with a BUF634T) to power the Ipod, but didn't try it in the end.

I'm not sure, but I'd guess the 5G does the same, so beware.
post #14 of 21
Thread Starter 
Hold on a second, you were using the SAME thread to power both? Or are you saying that whenever any power is connected to the IPod that the output audio ground must be physical ground, not virtual?
post #15 of 21
Quote:
Originally Posted by FallenAngel
Or are you saying that whenever any power is connected to the IPod that the output audio ground must be physical ground, not virtual?
Sorry, you've lost me there. How do you distinguish between virtual / physical ground?

But I'll just clarify again, that may answer your question:

I used one and the same TREAD to power a Pimeta and my Ipod. Since the Ipod ties Firewire GND to audio GND and FW ground is connected to V- to power the Ipod this counteracts the railsplitter in the Pimeta (which holds IG halfway between V+ and V-).

So if you're using the TREAD for your Ipod only AND your power supply is isolated (Tangent explains the isolation issue better than I could, read the section "wall supply issues") you won't have any problems, since then the Ipod audio GND floats independently.
However if you use the same TREAD for the Ipod and the Pimeta in your sig, then you'll run into said problem.

Helpful?
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