$500 for help with project [CONTEST]

[tanguero]

Thanks for the post. We will try this tomorrow.

[tanguero]

It looks like you have the answer.

Please contact me off-line: rf_parker@yahoo.com

[oPossum]

To use a Mintyboost V3 for iPad charging at 2A rate...
Use the USB connector and resistors R1, R3, and R4 as supplied with the kit.
Use a 43.2k 1% resistor for R2, or 10k and 33k 5% resistors in series (as pictured).
Ground lead is the same, use anode of D1 as +5.2V supply.

[oPossum]

Here is a complete schematic of the 10W iPad charger..



It is a very ordinary switching flyback power supply - nothing special.

The output voltage is set by R8, R9A and R9B.

R9A and R9B are in a parallel...

(10 * 110) / (10 + 110) = 9.167

Voltage calculation...

( 1 + ( 10 / 9.167) ) * 2.5 = 5.227 volts

[oPossum]

Schematic of the Griffin Power Jolt for iPad...



It uses the very common 34063 switching voltage regulator. A MOSFET is used instead of the internal switch transistor to increase the max current.

The output voltage is set by R6 and R7.

( 1 + ( 15.8 / 4.99) ) * 1.25 = 5.21 volts

The D+/D- resistors and the USB connector are on a separate circuit board joined to the other by two solder joints that carry ground and 5.2 volt supply. It could easily be separated and used with any 5.2 volt 2 amp (or more) power supply.

[suteil]

Hello, can anyone measure what is voltage is over LF1 A1 and A2 contacts, in ipad charger schematic?

[RSmike]

I owe you guys some feedback since I was working on a method to charge a Ipad from a 36 volt source and was running into problems that I since solved.

I'm using a V-Infinity power suppy to convert 18-72 volts (wide range) into 5volts DC (trimmed to 5.2v). I was having problem getting the iPad to charge. I had my voltages correct set on D- and D+. I had 5.2v to USB power.

After hours of testing.....I forgot about voltage drop. DUH. I had an old USB pigtail that I was plugging in to the iPad cable. It was about 10 feet. Sure!! Try to push an amp or better over 10 feet of 26 gauge wire. It's like trying to blow up a garbage bag with one puff of air. When I finally realized my error and chopped off about 9 feet of cable....ta-dah!! I'm charging.... I feel so stupid since this is EE101 stuff. I can only laugh at myself. I thought I would share my error.

I'm wondering if the shield actually needs to be grounded. Anyone messed around with this?

I'm also looking for either a very short large wire guage USB extension cable and/or a source for the iDock connector so I can make my own cable. I need to mount my power supply far away from the Ipad but I still need to deliver full current. If I can get 16-18 wire right to the device I won't suffer so much loss.

Thank you for all the work from oPossum.

RSLater,
RSmike

[azmat]

oPossom,

i have implemented the charger circuit using MC34063 IC but i am having a problem that when i used a 10W 2.2ohm resistor to replicate IPAD( as a load ) . the output voltage of the circuit falls down to 2volts. can you help me in this. also can you provide me the component list so that i can know the exact values of the components , since the component values are not mentioned in the circuit.

regards
Azmat

[azmat]

sorry forgot to mention, some values of the components are not mentioned.

regards
Azmat

[blakebr]

This is the circuit I built for testing the behavior of various iProducts. It uses ordinary 5% resistance values and has a jumper block for setting the max current draw.

Image removed for brevity.

1% resistors could also be used...

Image removed for brevity.]

oPossum,

A couple questions please. In your evaluation network (47k, 47k, 18k, 47k) my calculations say the tap voltages will be 1.53v and 2.13v. Normally the voltages are shown to be 2.0v and 2.7v (43k, 31k, 49k). Is there a difference in the way an iDevice will react to the different voltages? Must the 1.53 & 2.13 voltages be used to get the 2A charge rate for the iPad? From your two videos it looks like you use the 47k, 47k, 18k, 47k network for all 3 tests. Does the iPad 3 behave differently than the iPad 2? When you set the evaluation network for 0.5A charge, the iPad showed it was drawing about that amount. Is that indicating that the iPad is running off the charger but not charging the battery?

Thanks for your help,
Bruce

[cophian]

I think you will find 1 of the 47Ks is a 4k7 hope this helps

[blakebr]

I think you will find 1 of the 47Ks is a 4k7 hope this helps

I have looked and can't find out how many ohms 4k7 equates to. Do you know where to find the answer? Is it 4,000? If I use the 4k value the numbers come out right. Thanks

[adafruit_support_bill]

4K7 = 4700. The 'K' indicates both units and the location of the decimal point.

[blakebr]

4K7 = 4700. The 'K' indicates both units and the location of the decimal point.

Thank you. I used a 3.9K (3k9) resistor and things are working. I have been working in electronics since 1963. I guess they are adopting new coding methods just to confuse me. FYI - We have an iPad 2, iPad 3, two iPhones and an iPod. I want, and need to build, one charger that will charge all our iDevices plus those of our son (iPad 2, 2 iPhones) at the same time (8 iDevices). A 20A 5V power supply from eBay is the start. The information from your site filled in the blanks. Thanks!

P.S. I used one resistor ladder and it seems to work just fine.