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

USB chargers are one of the most popular things to build here on Instructables. However countless people have been disappointed to find out that after all of their hard work, their iPods just sit there and do nothing, despite receiving 5V.

Recently my USB car charger died. I thought it'd be great if I could just install USB ports into the center console, and I totally did too. But the iPod wouldn't charge, so I scoured the internet looking for an answer. I found out what I needed to do was put resistors onto the data lines, but nobody agreed on what resistors or even how to hook them up. Finally I just ripped apart my broken USB charger to see how they did it.

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

[joeledmund]

for the itouch 4th gen i use 2x 100k ohm put on both on the plus side of battery and one lead to each data line

[The nerdling]

i tried using this idea but it didnt work
this is not a link

[iApple guy]

Will it work with the newest iPod nano?

[ElectroFlex]

Would 1/2 watt resistors work?

[mermeladov]

I have a Wireless router WBR 6800 which has a usb port for 3g or 3.5g internet connection but I wondered if this thing would charge my ipod so I connected it and it seems to be charging. However I'd like to know if this is safe or recommended. Have you guys ever tried this?

[trevorrock88]

I wired up a breadboard and used potentiometers to get exactly 2.7 volts out of D- and exactly 2.0 volts out of D+. My iPhone 3GS charged... but at 0.481 amps. I thought this was supposed to make the iPhone charge at 1.0 amps? Has anyone gotten 1.0 amp out of this configuration?

[mpilchfamily]

It doesn't force the phone to use more current when charging. It only tricks the phone into thinking it has a data connection and its safe to enable charging.

Why would you want the phone to charge at 1A. If you force that much current into the phone you may damage something. FYI, the USB spec only calls for an output of 5V @ .5A. So less then .5A is all that is needed to charge the device. Also keep in mind the 7805 outputs 5V and has 1A of current available that doesn't mean your device will pull that much amperage.

[mpilchfamily]

This is a great instructable. It has helped me allot in my current project and a link to this instructable will be included in the instructable i'm making. The charge circuit i used is very simple and offer 5.03V. Based on that i went to my trusty Voltage Divider calc to find a good set of values from the resistors i had on hand. Here is what i came up with:
- R1= 22K Ohms
- R2= 26K Ohms (1x 22K resistor and 1x 4K resistor in series)
- R3= 15K Ohms

When i first connected everything on my breadboard for testing the voltages came out wrong. So i flipped the resistors, putting both R1s on the Positive side and R2 and R3 coming off the Ground Lead. After checking the voltages across D+ and D- everything looked good so i plugged in my 2nd and 5th Gen iPod Touches and they where charging.

Thanks again for the info about the voltages on the data lines needed to enable charging.
Here is my schematic:

[rmosby]

Thanks. This instructable has great diagrams to go off of. On several broken car chargers that I have taken apart, there as also an inductor included in addition to the decoupling capacitors and the diode.

Would an inductor be a wise thing to include to help filter out the starter-motor's noise? And if so, are there things that need to be considered when choosing an inductor? Size? Core type? I don't want to inadvertently make a resonator circuit and do not (yet) have the mathematical knowledge to make an informed decision.

[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

[Fiki2007]

I just wanted to let people know who are doing this that the resistor value for R1 is for two individual 49k ohm resistors and not just one. I thought that initially then thought maybe two 25k ohm resistors but decided to try just two 47k ohm resistors which worked for me.

Also as other posters have stated, there seems to be a very wide range of what resistance is required in order for this to work. Pleasantly surprised everything went off without a hitch my first attempt, a fantastic instructable. My only recommendation would be to change one of the R1's in the schematics to a R4, especially since the third picture shows a R4.

[mcarrell]

R4 is used on the input side of the power regulator, so I agree, having two R1s may confuse people.

IMHO, R4 should become "R5" and the R1 which is paired with R3 in the left hand voltage divider branch should be changed to R4 to make this circuit more understandable for those with less experience in electronics so you end up with an R1/R2 voltage divider on the right and an R3/R4 voltage divider on the left of the two voltage "divider diamond".

[astrickland1]

will the increased voltage the 5v in the + and the 2.7 in the D- and the 2v in the D+
fry other phones or devices

[mwhite22]

Well I think I about lost my sanity on this thing, heh. I could NOT get the voltages right. always came up as 5v. finally got a light in there at just the right angle and realized what was touching somewhere it shouldn't have been. Anyway waiting on the hot glue gun to warm up now so I can seal that nonsense tight before I put the resistors back in line :)

[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.

[Fiction]

Any word on what is required to charge iPhone 4's and iPad 1/2's?

Is this circuit all that is required? Or is it a more complex chip as others have stated?

[ckrill1]

does the amount of ohms matter if you use 1/8 watt resistors?

[Turnbull.angus]

So I understand that this setup will allow you to charge any Apple product, but what about other devices such as my htc evo? I'm trying to make a device that will charge anything that can be powered from USB, not just apple products. :) thanks in advance!!

[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.

[furrysalamander]

Could you get me the resistor color codes?

[jkmerlin]

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

[thepaul1993]

Will this charge the 160GB iPod Classic?

[joshnosh]

it should charge any ipod

[blackbelt27]

im pretty new to the world of circuits like this and im somewhat confused, from what ive learned your using the resistors in a series as voltage dividers. if voltage is the only thing, that the data and power pins require to be specific, then why not use the least ammount of ohms to keep up the ammount of amps? to make the charging faster because from what i understand resistors by themselves only affect amperage

[joshnosh]

yes it is like a voltage divider
the 5v and 0 pins are still used to do all off the charging to the device
the data lines just tell the ipod it can charge (most likely so you can only plug it into a apple charger)
the data lines just need a set voltage. it consumes a very small amount off amps and none off that goose into charging the ipod

[makincoolstuff]

do the resistor ohms have to be exact?

[makincoolstuff]

wait it works, awesome, thank you so much. i just replaced r1 and r2 with 47k ohms and r3 with 100k ohms. works just as well, in fact, it charges really quickly. it also charges all the devices ive tried on it (nano video, nano, ipod touch 3rd gen, iphone 3rd gen) thanks again.

[lleemans]

i have mine working with ipod nano. but if i try my ipod touch it works for like 1second and then it stops working. i think couse i used like 5.5V and not 100% correct resistors.

[buddybran]

Would 1/2 watt resistors work?