This is an electricity question so I figure someone here could help.

The new ipod, santa brought, no longer works with my old ipod dock. Apple has changed the pins and charging voltage of the new ipod so, while the old docks will play music, they won't charge your ipod while doing so.

My question is this. I figured I could resolder the pins, on my old dock, to correspond to the pins which charge the new one. The old ones were fire wire, and the new ones usb.

The main problem I see, would be that fire wire's output was 12v whilst usb is 5v. So if I resolder the pins, I need to first introduce a resistor into the circuit to lower the voltage. At least that is my idea. Granted, my understanding of electricity, is limited to the experiment set I bought at radio shack, for me and my daughter, a few months ago. Which has been a ton of fun by the way.

I know the other problem I am going to run into is amperage. The difference in amperage between the two. I am not sure what the difference is right now but I am digging to figure that out as well. I will post more as I figure it out but does any one have any preliminary suggestions to point me in the right direction.

So some initial questions:

Is it possible, using a resistor, to step down voltage from 12v to 5v?
Is it possible to step down the voltage as well as the amperage? Is it possible to step down the voltage while boosting the amperage?

Thanks for the help!

 

You really can't use a dropping resistor, as it would only be accurate for a single level of current. A voltage regulator like a 7805 is more the thing to use. Even the Shack should carry them. You can always get a data sheet to see about the pinout (for TO-220, it's in, ground, out).

Loads use the power they need. If you stabilize the voltage, then the current will vary with charge on the internal battery. As the regulator will be wasting 7 volts, you may need to attach it to a heat sink so it doesn't get too hot and shut down.

 

Hey, thanks for the reply.

I think I may need to start studying the manual, on the main webpage, to comprehend everything you laid out, but, reading it over a couple times it makes sense.

I wire the 12v line into the left side of the regulator, the ground(s?) to the center, and the right side to the pin on the dock. Thus giving the proper 5v to the device.

I think the heat sink can also be found at the shack. The only question I have on that, is attaching it to the regulator. My guess is, it sits on the metal tip to add to the heat dissipation.

Would you recommend the heat sink grease, they sell, as the best thing to attach it?

Again, thanks for your time.

 

There is a hole in the tab on the regulator, so a #4 screw and nut will work fine. The handy thing about a 7805 is that the tab is also ground, so it usually doesn't need insulation.

 

So I picked up the regulator today at Radio Shack. I can't believe how disorganized the electronics racks are over there. It was a mess but some how I dug one up. Of course they didn't have the heat sink, but, they're going to send it to me, free shipping! Can't beat that.

I am going to pull the dock apart later this evening and take a look at the innards. I am sure more questions will be popping up so I hope you don't mind answering a couple more. I really appreciate the help!

One thing is, I thought I might wire it up, test it, then wait for the heat sink to arrive to put it fully into use. Would that work, or will it get too hot too fast, and should I just wait on the heat sink?

 

You can always see how it does. The regulator will shut down if it gets too hot - which is too hot to handle, by the way. Really warm is not a problem.

 

There's a hole in the regulator, dear Liza, dear Liza....

So, I pulled the sucker apart and then it pulled me apart (mentally, metaphorically speaking!)

Here are some photos of the mess I made. What I gather from the little I understand...I need to put the resister in between the wire, which is coming off the board, that is labeled +9v (purple) and connect that to the 5v charging pin on the ipod dock (the little blue board I am holding in the photos).

From what I found here, it seems that I found the pin I need to solder the 5v wire to. Another question I have? does the ground go, from the board, into the regulator, then out to the ipod dock ground pin?....Sorry, I am little confused.

Another one, how do I solder things so small?

Thanks again for the help.

 

Reading the bottom of the page, which I linked in the last post, it says:

"iPod Nano 4th Gen no longer will charge from 12 volts on the firwire pins. If you tie pins 25 and 27 together through a 10K ohm resistor while applying +/- 5 volts to pins 23 and 15 (or 16) that it will charge. If you don't tie 25 and 27 together, it won't charge"

So, I use the regulator, attach it to pins 23 and 15, then I would need to solder a 10k ohm resistor between pins 25 and 17?

If that be the case, my question about the ground on the regulator still remains. How does that work?

Thank you, kindly.

 

Well, the grounds are all common, so they should all tie together.

I have to say that the information is a bit less than comforting. I would search further for some confirmation - say an iPod forum - before making those changes. The possibility of damage to your iPod seems slight, though, with only 5 volts applied.

The part that makes me a bit iffy is the note about +/-5 volts. He may mean +5 and ground, but an electronic person sees that as applying both positive and negative 5 volts. That bit of information needs to be verified.

I'd also send a nastygram to Mr. Jobs about the lack of hardware compatibility.

 

I see what you mean. I hadn't thought about that.

The reason I ended up here with you, discussing these questions, is because my search on various ipod forums gave me no help. A lot of people reported the problem, complained about it, but it didn't seem there was a lot of people pulling their stereo docks apart and fixing it.

But, I could post up the info from the .ru site and see if anyone gives me some feedback on whether or not that will work. Thanks.

 

It works. I attached the regulator (and the resistor as the .ru site outlined) and my dock now charges the ipod touch (2g) when attached.

The regulator is hot to the touch, so, before I put all the screws back in, I am going to wait for the heat sink to get here.

Thanks for all your help!

P.S. And next time, or for anyone else who reads this, get one of these dock connectors before you attempt to mod your dock! It will make the soldering SO much easier.

 

So i've attached an image of the PCB my dock is mounted on. My plan is to cut the trace from F/W Pwr+, connect this into my voltage regulator and then from the regulator out to pins 23 & 15/16/any ground. Stick a 10k ohm resistor in between 25 & 27 and all should be good right?

(if you look at the PCB i think i can hijak the F/W Pwr+, F/W Gnd, USB-, USB+ & USB PWR headers to achieve my connection to the required pins. Can somebody confirm this for me please?)

The next problem is that i was only able to obtain an adjustable voltage regulator and im not sure how to limit this down to the 5v i require. Datasheet Here.

Any help you guys can provide would be much appreciated.

Cheers

Phil

 

Let me preface this post with the current status of my own dock work:

Well, for my own progress, I received the heat sink so now I can finish off the power for the ipod BUT, it requires a screw to attach it to the regulator, which it didn't come with it. So, I am still not able to finish it off, yet.

Secondly, my ipod charges from the dock as I mentioned BUT, it doesn't play sound through the dock speakers any more. Why? I do not know, I haven't touched the sound pins, so I don't know why this would happen.

So, I now have a dock that charges my ipod, but won't play sound anymore (sad face).

What I think I will do, is get the dock connector I mentioned above and just rewire the whole thing. Unless of course I figure out how to fix the sound without doing that.

Phil, the data sheet for the regultor says:
Output voltage range:285 to 36V

You need to get the thing down to 5v. To be honest, I don't have a clur of how the regulators work, I just took "beenthere"s advice. Hopefully he will comment here about it. Otherwise you could pm him, referencing this thread, and your problem.

I take it you are in the UK so you don't have radio shacks there?

 

Success for me also, purchased myself a nice 5v regulator, wired up as detailed on previous post and all works brilliantly. Thanks for the info and help guys!

If anyone needs any info on this project feel free to PM me.

Cheers

Phil

 

Hi,

I've been spendinga day or tweo getting this working on my Klipsch iGroove.

My Ipod Touch is charging as I type, but it wasn't so straight forward as other people seemd to have found it.

Firstly, I stuffed up by wiring the resistors to the wrong pins. The iGroove PCB labels pin 30 as pin 1 and it took me a while to realise my mistake.

Nevermind, when I put things the right way round it was a lot easier anyway as pins 23, 25 and 27 all have pads and vias on the PCB, even though they don't go anwhere - thanks to the Klipsch eCAD team for that!

I measured it all out and everything was fine so I attched the iPod.

I powered up and it started charging with triumphant little chime but not for long. After about 30 seconds the charging icon switched back to the battery statis icon. Then a few seconds after that it chimed again went back to charging - and so and again. It was oscillating bacwards and forwards. In fact the 5V rail from the regulator was jumping up to nearly 15V (just off the supply rail voltage) and then diving back down before settling at 4.8V again.

Well, I slept on the problem and today I've added a 5V zener and 100uF cap across the 5V rail and ground. It's still undulating a bit but only between 4.6 and 4.8 V. With no cap attached it actually oscillated much worse and the chime was going on like crazy.

It's sort of okay now but I want to see it charge up notch before I'm convinced it's working properly. Also I've screwed the regulator to the PCB and I'm not convinced it's disspiating enough heat as it's pretty hot.


Can anyone explain what is going on here? I though the regulator (LM7805) would be constant voltage but it seems not. There must be enough current from the iGroove as it would have had to supply enough for the firewire.

Anyway, thanks for the help on this thread and hopefully this will help others get their old docks working.