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$500 for help with project [CONTEST]
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$500 for help with project [CONTEST]

by tanguero on Fri Aug 06, 2010 11:19 am

Hello.

I need a solution to mod the MintyBoost to charge an iPad. My source is a 3-amp openframe power supply at +5v.

If you study the postings by Adafruit you will see they have systematically solved all new product introductions except the iPad because they only work with batteries and the iPad needs a lot of power. I do not work with batteries so I have plenty of power.

Terms:
email me or respond to this posting (I do not give my email here because I am not sure of the forum's rules - but I will if it is OK). If you enter, I will pay for all of your expenses in solving this problem.
If you are the first to solve the problem, I will want a diagram and a cell-phone video where you explain the principals. You will receive the $500 on top of your expenses.
Contest limited to five (5) participants. You will be a participant by registering with me at this forum.

You can call me at 561-843-7346 (my apologies if I have broken a forum rule here).
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Re: $500 for help with project [CONTEST]

by oPossum on Fri Aug 06, 2010 11:50 am

Image
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Re: $500 for help with project [CONTEST]

by tanguero on Fri Aug 06, 2010 1:13 pm

Hello.
I believe I have tried this with no success on Wednesday. This looks like the iPhone charger.
Have you tested it with an iPad?
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Re: $500 for help with project [CONTEST]

by oPossum on Fri Aug 06, 2010 1:34 pm

The latest iPhone/iPod charger is 1A and uses the resistor values shown. That is the max, so measuring less current does not mean that the 1A charge rate is not being used.

The iPad charger is 2A (10W). Do you want a max 2A current draw?

You should edit your post to be very specific about what you want. Saying you want to mod the MinyBoost, but have a 5V 3A power supply really makes no sense.
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Re: $500 for help with project [CONTEST]

by tanguero on Fri Aug 06, 2010 2:49 pm

Actually, I disagree.
I do have a 5v 3A supply and I have been unsuccessful with resistor divider networks to get the iPad to even show a minimal charge or that it is in the charging cycle.
I thought I could use the MintyBoost as a platform and then adjust the components until the iPad charging scheme worked.
I would like two circuits: charge the iPad at 2A and at 1A.
Please tell me what you tested this circuit on and the results.
I will test it on Monday.
Thanks.
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Re: $500 for help with project [CONTEST]

by tonythemediaguy on Fri Aug 06, 2010 4:03 pm

This makes no sense. Just use an iPad charger.
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Re: $500 for help with project [CONTEST]

by tanguero on Fri Aug 06, 2010 4:25 pm

Well - there must be a reason for doing what I am doing, correct, else why go through all of this?
Of course I can use an iPad charger. For reasons which you do not know, I cannot use the iPad charger. I have to use another power supply which is +5v capable of 3 amps.
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Re: $500 for help with project [CONTEST]

by oPossum on Fri Aug 06, 2010 7:47 pm

I'll have a schematic of the 2A charging circuit and a video on Monday.
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Re: $500 for help with project [CONTEST]

by tanguero on Fri Aug 06, 2010 9:29 pm

OK - that sounds very helpful. Looking forward to it.
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Test results with oPossum's circuit

by tanguero on Mon Aug 09, 2010 1:55 pm

Hello.
Thank you for the circuit.
I tried it and got exact voltages on the data lines as needed.
It still does not work.
It will not charge the iPad.
There is something else going 0on here...
any guesses?
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Re: $500 for help with project [CONTEST]

by oPossum on Thu Aug 12, 2010 2:55 pm

Sorry I didn't have time this past weekend to make a video. I think I will be able to do it this weekend.

This is the circuit for 2A max current draw:

Image

  • The voltage at the USB connector should be 5.10 to 5.20 volts. Most power supplies have an internal trim pot to tweak the output voltage.
  • Use the USB cable that came with the iPad. Don't use a generic cable or another Apple cable.
  • The MAXIMUM current draw is 2 amps. It will usually be much less.
  • The highest current draw will usually be when the battery is 20% to 70% charged. The charge rate slows as the battery reaches full charge. If the battery is 80% charged or more, there will not be much current draw.
  • Use an amp meter (or bench supply with amp meter) to determine if this is working properly. Don't rely on the iPad's charging indicator.

Here is a picture of the resistors in an iPad 10 watt (2 amp) charger:

Image

These are 1% resistors, so the markings are a code, not the literal resistance.
The 'C' suffix means multiply by 100.
62 = 432, so 62C = 43.2k
68 = 499, so 68C = 49.9k
85 = 750, so 85C = 75.0k
Last edited by oPossum on Thu Aug 12, 2010 4:24 pm, edited 2 times in total.
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Re: $500 for help with project [CONTEST]

by oPossum on Thu Aug 12, 2010 2:59 pm

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

1% resistors could also be used...

Image
Last edited by oPossum on Tue Sep 21, 2010 11:11 am, edited 1 time in total.
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Re: $500 for help with project [CONTEST]

by tanguero on Sat Aug 14, 2010 3:02 am

Thank you very much for this well expressed submission. I am in Sweden at this time, but will return to the US next Wednesday and will have my tech try this out.
Looking forward to the cell video.
We were unable toget your first circuit to work, but we may have missed somehting.
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Re: $500 for help with project [CONTEST]

by oPossum on Thu Sep 09, 2010 2:31 pm

Here is a video of 2 amp current draw (50 MB Quicktime).

Here is another video showing 500 mA and 1 amp current draw (35 MB Quicktime)

The video is not on a streaming server, so right click and download the file.
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Re: $500 for help with project [CONTEST]

by tanguero on Thu Sep 09, 2010 4:02 pm

Thanks for the post. We will try this tomorrow.
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Please be positive and constructive with your questions and comments.