Iphone charging...

Pin 1 voltage levels from 4.5V to 5.25V, the actual current drawn by the device varies

Silicon chip ran an article (August 2013 ??) on the voltages required on both USB pins to make the various Apple products draw their full capability.

It seems that unless the Apple device sees that voltage, it won't use the full current draw of the supplying device (ie 5v x amp supply)

It was quite interesting because the ratios of resistors required was not simple.

Mark

shabaz wrote:

 

Also, it is only intended for 500-600mA at best (and possibly less), so I don't get why you think this would be useful to charge an iphone in the first place - would take many hours and probably not healthy for your

expensive iphone in the long run.

This is a $0.99 circuit, not really designed for iphone charging although it might get you some charging with the relevant resistors and confirmation that the voltage is accurate as

advised.

 

If you want to do it properly, there are tools to help you design the desired output voltage and current capability and build your own circuit but you'd need to be prepared to solder the parts up yourself (some parts may be surface-mount).

But for a one-off, purchased parts will cost far more than an off-the-shelf iphone charger.

 

You could try looking for an alternative module from ebay but this $0.99 one is pretty poor for what you're trying to achieve.

Fully agree with these points. I'm very doubtful that you will get the stated power output with this module anyway. An official Apple charger typically outputs 5W (1A) of power.

Also, judging from that photo in your first post, it looks like there is a tiny capacitor (maybe 100nF?!) on the output, so the output may not even be very clean. Could cause issues.

[EDIT - sorry - looks like there is a 100uF cap on that thing on the output side - I was accidentally looking at the input side in the photo].

Also, it is only intended for 500-600mA at best (and possibly less), so I don't get why you think this would be useful to charge an iphone in the first place - would take many hours and probably not healthy for your

expensive iphone in the long run.

This is a $0.99 circuit, not really designed for iphone charging although it might get you some charging with the relevant resistors and confirmation that the voltage is accurate as

advised.

If you want to do it properly, there are tools to help you design the desired output voltage and current capability and build your own circuit but you'd need to be prepared to solder the parts up yourself (some parts may be surface-mount).

But for a one-off, purchased parts will cost far more than an off-the-shelf iphone charger.

You could try looking for an alternative module from ebay but this $0.99 one is pretty poor for what you're trying to achieve.

Check your voltages:

A general observation with the Apple products is that they will attempt to draw the maximum current if and only if the voltage level on Pin 1 with respect to the current draw remains constant between 5 and 5.25 volts.  Often, if a charger is unable to supply the proper amount of current the voltage output will drop.  For instance, a 5.25V 1A power supply may only output to 4.5V when under a 2A load.  For Apple products, when a device is presented with any one of the voltage configurations (500mA, 1A, or 2A) and then presented with a range of Pin 1 voltage levels from 4.5V to 5.25V, the actual current drawn by the device varies.  In our tests, we found that when the voltage sent to the iPad 2 was 4.5V, the iPad 2 drew only about 1A, but steadily scaled up the current to 2A as the voltage was incrementally increased to 5V.  Additionally, we noted Apple devices will not accept charge from power supplies with Pin 1 voltages of less than 4.5V or greater than 5.5V.

Extract from Peri's link: http://www.voltaicsystems.com/blog/choosing-usb-pin-voltages-for-iphones-and-ipads/

i have tried 2,75, 2,8, everything now... NOTHING it still says accesory not supported! i've even tried with 2.0 v on both data + and data -, and nothing. PLEASE HELP! i initially thought this was THE ANSWER but nope, not really, still doesnt work. help... please, im losing hope here.

http://www.voltaicsystems.com/blog/choosing-usb-pin-voltages-for-iphones-and-ipads/

Seems that different iphone versions behave differently. Quite picky about voltages at datalines. 2.75V D- and 2.00V D+ seems to work best.

PS3 controller is even worse: It needs to negotiate with a host to initiate charging. I used a ATTiny45 and V-USB, but it works.

This article may help.

https://learn.adafruit.com/minty-boost/icharging

They seem to be trying to achieve exactly the same goal you are.

Now that i applied resistors the phone says "this accesory may not be supported " please help!