How to get your iPod to charge with your homemade charger.

Step 1 Schematics

First off I should mention that this is supplemental Instructable to the countless others that show you how to build a USB charger. I am assuming you've already made something that can supply 5 volts DC. I assume no responsibility for how this jives with your 5V power supply or the USB devices you connect to it. All I really know for certain is it works perfectly with my 4G iPod, my Energizer USB-powered battery charger, and my cellphone.

OK, here we go.

The values of the resistors in the schematic below can be approximate. Those are just the values I measured from the resistors on my dead car charger. You could also hook up different valued resistors in series to dial in the exact ohms (22K + 22K = 44K, perfect for R2.) Also, 1/8W resistors will work just fine.

Once you build the circuit, test it. You should get around 2.7 volts out of D- and 2V out of D+. This may seem scary high but it's in the USB spec for signaling a USB 2.0 connection. This is how the iPod knows it's OK to draw the power it needs to charge.

Comments

[jbyrns1993]

Do I need a heatsink on the LM7805 if I'm running this off a 9V 550mAh battery?

[Rainh2o]

The LM78XX family can not be burned up. They are internally regulated for temp, so they get hot, they stop working until the temp drops and then they reset and start working again...you can short them out totally and actually use them as heaters for small projects. They are tough.

[legless]

Well here on Earth a 78xx reg certainly can go up in smoke and I've seen it happen several times.

[Rainh2o]

I have NEVER seen them burn up...we used them in lots of weather research equipment to keep the inside of the boxes warm in below freezing conditions...the data sheets say they are thermally protected, also overload protected

[mcarrell]

They'll burn up quite easily. I have roasted many of them because of too demanding of loads placed upon them. It seems their internal protection circuitry isn't that good.. Back when I went to ITT my graduation project was a laser show in a briefcase. We used LM7805 to get 5 V from our rectified transformer output for driving our audio level detection and main logic circuits. Unfortunately, we found after blowing several of them the only way to make them work for the long term was to put pretty good heat sinks on them with thermal paste. Cheesy heat sinks or those without basic thermal paste weren't good enough to keep them from overheating.

[Rainh2o]

Maybe the cheap .10 cent ones from China, the good ones from Fairchild or National, I have never burnt up and have even used them as heaters in the winter on several prototype equipment by shorting the output directly to ground. They get hot fast and then go into protection mode, then when they coll enough, they come back on...put them on a sheet of aluminum and you can make a pretty good cheap, simple heater circuit to keep a small enclosure from freezing. I dunno, maybe the aluminum was good enough for a heat sink but I never burnt one up in several years the equipment was used. Did your supply have good ripple filter? I was using straight DC from a battery/solar panel so no ripple..maybe supply with some ripple is harder on protection circuitry or something.

[joshnosh]

if it gets too hot to hold your finger on it for more than about 15 seconds then yes

[zack247]

i would suggest yes, they do get kninda hot, so a heatsink would be nice

[plasma dragon007]

Doing this has gone way out of my realm of electronic knowledge, but I got it to work successfully and am currently charging my 80gig iPod Classic.

However, I have a question.  Since the - and + power lines meet (right?) because both R1's, R2, and R3 touch, would you then need a diode on one (or both?) power lines to prevent power flowing back to the batteries?

[legless]

Yeah the rails do not "meet". As well as placing a voltage on the data pins to tell the iPod that a charger has been attached, the resistors provide a load across the power supply. The device you are charging will add to the load as well. The value of the resistors and therefore the voltage on the data pins may well tell the device what sort of attachment has been connected - such as a charger or a headset. This is what happens with many Motorola phones like the RAZR2 V9.

[Thermiter]

The power lines don't meet, and the resistor values are high enough that this only draws like 20 uA.  I don't quite understand why you think you need a diode, but it seems to me that you don't know a lot about electronics, don't sweat it.

[tomtortoise]

Can someone please tell me the color codes for the resistors.

[amesj]

49.7k approx 47k = yellow violet orange then gold or silver
43k = yellow orange orange then gold or silver
74.9k approx 75k = violet green orange then gold or silver

[Archive555]

Google can.

[misteravocado5]

 Does anyone happen to know what the charging voltage for the ipod touch is? I called Apple and one guy told me 12V 2A, but this seems high.

[bcuzimfly]

5v Standard USB Voltage.

[Thermiter]

That's for firewire charging. The firewire protocol is 12v, the USB protocol is 5v.

[misteravocado5]

So just a normal USB output, right?

[Thermiter]

Yeah, just with those resistor values on the data pins to force charging.

[it_dont_work]

my ipod will charge from a 30v source to about 1.5A, i dont know if the touch will work that way, but thats the output from my firewire charger

[Rayadillo]

Can anybody put up a picture of this, i kinda dont understand :/???

[salinations]

Hey! I have a question. I made that circuit, well not the same, I made my own voltage dividers with smaller resistors (around 1KOhm) and I have 2.6V in D- and 2.1 V in D+ (I'd verified it with a multimeter) so, the only difference with this schematic will be the current in the data pins. So I connected me iPod 3rd generation to the circuit and... is not working, so I measure the voltage with the iPod connected and I don't know why, but the voltage raised up, with the iPod connected I have around 4.5V in both data pins, and with the Ipod unplugged there are the 2.6V and 2.0 V that are needed . So, does anybody know why is this happening? Is the current? or It could be that is and Ipod and not an IPhone? Any idea?... thank you!

[salinations]

Hey sorry is a 4th generation Ipod, not a 3rd G. Thanks

[Thermiter]

The problem has nothing to do with firewire.  The problem is that the ipod itself has a certain amount of resistance between the power pins and data pins.  when you plug it in, you basically connect those resistors in parallel, which screws up your resistor values and skews your voltage drops.  I would say that you need to use the right values.

[imkwl12345]

is it a nano 4th gen? cos they dropped the firewire when that came out so im not sure if this will work with that and later ipods

[Sitnalta]

Also, the 4.5 volts to the data pins is bad. There must be a short somewhere. Be sure the electrical contacts are free of flux or metal particles.

[Sitnalta]

You need at least 4.9 volts to charge. iPods are finicky about that. I would say that your voltage regulator is bad

[vitalzero]

There's an article at wikipedia for this usb thing: http://www.allpinouts.org/index.php/USB_-_Universal_Serial_Bus
which says: "To force charging of your iPod, PSP or any USB device, you have to force high the levels of the data pins 2 (D-) and 3 (D+) by connecting them to a +5V using a 10KOhm resistor." what do you think?

[leotris]

Cheers for this, I've been getting a bit fed up with other Instructables saying you only need to connect the red and black to charge an iPhone. Bodging an Iphone charging dock into a running machine is tricky enough (already had to replace a processor chip that i blew, gotta love eBay) 
                Although i did use a 2x 33k a 22k and 47k resistor setup as i had the parts already. love the way that every version of this I've seen uses different resistor values.

[RPW1963]

OK, this looks good BUT, can anybody explain (for this dummy) how all this goes together, I believe I have all the parts. Thanks

[faheyd]

Well, I haven't done it yet, but break it down piece by piece:

Solder '+' (positive) to R3 and R2

Solder 'R2' to D- wire,  and solder to R1-A (for simplicity)

Solder 'R3' to D+ wire, and solder to R1-B (for simplicity)

Solder R1-A and R1-B to '-' (negative)

(the little jump that D+ makes means that doesn't connect to the '-' (negative) wire)

Just work your way around the resisters and you should do OK.

[ormo]

Thank you very much :D I spent hour scratching my head over this, even destroyed an iPod going on someone else's suggestions (free replacement, AppleCare isn't so bad :P). Good to see someone who actually knows what they're doing with this. Mine has about 15 resistors in it - I couldn't be bothered to go and buy ones of similar value so I just bodged these values hehe (I ended up with something like R1 as 102K and 98K, R2 as 45K and R3 as 77K)

[aceopspadeshearts]

Hey, i made a solar ( free =D) charger and i'm planning on charging my iPod on it. Now i've read this article i'm doubting it'll work... I'm also using the LM7805 in my circuit; im using 5 little solar panels giving 10V aprox. and 30mA => leading to 2 9V battery's which are leading to the LM7805 and from there to a 3 way switch, which can be set to a Led light (flashlight built in !!) or the USB exit. Now im not knowing what kind of resistors i should use to make sure my iPod will charge??

Please if you can help me as fast as you can =) im leaving for egypt in 7 days so i've got little time left =D

Greetz

[luha]

Does the amperage of the power source matter?

[luha]

Also, does it matter if the capacitors have a higher voltage rating (such as 1000mfd 50v instead of 1000mfd 35v, and/or.1mfd 250v instead of .1mfd 63v)? Thanks for any help

[alex-sharetskiy]

if you use the lm7805, amperage doesn't matter it doesn't matter if the capacitors have a higher voltage rating, as long as they are rated for at least 5v

[willymakesstuff]

you should win the best inventor of the year no kidding everyone else that makes ipod charger instuctables r stupid except you thanks soooo much my ipod also thanks u cause now it charged from a nine volt battery and a 5 volt regulator

[willymakesstuff]

finaly somone really knows what there doing, thanks helped alot

[romeodog321]

how do i do this!!!!

[rkr]

So what you're saying is, basically, the iPod has to have power through the data lines too, in order for it to charge? If so, that would explain a lot.