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One of benefits of stocking open source hardware kits @ the Maker store is you can always improve upon the design or just do something slightly different - so here's a modification to the MintyBoost kit using a new boost converter chip to squeeze out even more juice. Ziemaginations writes -
...the most apparent change is instead of using the MAX756 boost converter chip, mine uses the newer MAX1675 boost converter. The biggest difference is in size, with the MAX1675 being many many times smaller. Also, this new chip does not require the use of an external diode to protect against reverse current (or whatever it did on the original Mintyboost, I did not look into it very much), increasing efficency by eliminating a major source of a voltage drop. All this adds up to a theoretical increase in efficency of up to 10%. The Mintyboost was rated at about 82%-84%, depending on the parts used. This chip is capable of up to 94%, but I lack the materials to verify that for myself. Also, my board design is single sided, allowing for easier fabrication at home. The single sided design, while easier, also removes the ability to add low battery LEDs...MintyBoost, Ziemaginations style - [via] Link.
Related:
Minty Boost Kit
Everything you need to make your own small & simple, but very powerful USB charger for your mp3 player, camera, cell phone, and any other gadget you can plug into a USB port to charge! Uses 2 AA batteries (not included), more than doubles your iPod 4G/5G battery life! - Link & get it at the Maker store.
YES, EFFICIENCY!!!
What I'm curious is compatibility. One of the reasons the MintyBoost became a two-sided-pcb endeavor was because of the need to add a few resistors to get some older (and newer) iPods to charge... maybe this MAX1675 package handles that problem? Maybe not...
*Looks further into link...*
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"Get it at the maker store": http://store.makezine.com/ProductDetails.asp?%20ProductCode=MKMINTY
You've got a spare space after the '?'
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rats, its fixed now - thanks shadyman
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Honestly, I don't know if its 100% compatible with the original MintyBoost. The MAX1675 has different pin locations, which allowed me to put both resistors on the single sided board, but without a device that uses the D+ and D- lines of the USB (the GBA and DS mentioned in my article only use the +5V and GND lines), I cannot test that they actually work or that I have them in the correct orientation. I attempted to correct for the iPod issue mentioned at Ladyada's forums and on the official MintyBoost website by doing the R5 hack in the copper for you.
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Hi Ziemaginations,
Few questions:
1. Have you grounded pins 2,3? MAX1675/1674 spec recommends to do it if LBI/LBO are not used
2. In your schematic R1 goes from V+ to USB pin 3 and R2 connection goes from GND to USB pin 2. It is different with Ladyada's v 1.1 - Her R4 goes from V+ to USB pin 2 and R5 goes from GND to pin 3. Who is right?
Thanks
4public
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