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USB Charger 2.0 Answered

ok, member GoodAtIt wont reply at all, i have double all the parts for his usb charger 2.0 but all i want to know is how to make it into a double thing he did by putting 2 together to make one, someone help out. double the picture i posted thing.

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gmoon (author)2008-02-18

It is a bit difficult to decypher your post... But you want a dual-output charger (two USB ports), right? All you need is a second USB port, connected in parallel with the existing one. You'll need to change the PCB traces if the orientation of the ports is such that one blocks the other. Also, if the current draw of two USB devices is too much for a 9V / 7805 pair, you could use two 9V batteries together in parallel (two in series would work too, but the 7805 would just dissipate the extra voltage as heat..)

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Yerboogieman (author)gmoon2008-02-18

well its like 2 processors if you only have one it works pretty hard, 2 processors that one works less hard, 2 portable chargers integrated into 1 to make the 1 regulator get less hot and not have to work as hard

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gmoon (author)Yerboogieman2008-02-18

A couple points:

-- 7805 regulators are inefficient. A 7805 in combination with a 9V battery is at best 60% efficient. So you're loosing 40% of your current to heat, etc.

Using two 7805 regs will double your losses, not reduce them.

-- The estimated max current that a 9V battery can supply through a 7805 is 300mAH (60% of the battery capacity), even though the 7805 can source ~1 amp (1.5 with a heatsink.) So two or three parallel 9V batteries still aren't enough to overtax a 7805.

And at that rate of discharge, a single 9V battery will drain below the 7805 minimum voltage in an hour....

-- Lastly, if you really want to use two separate regulators (meaning you're planning for a larger current source than a 9V battery or two, and you intend to drive both regulators hard), then you need to replicate the entire circuit twice, since the caps are required for reliable operation of the the 7805 (the LED would be optional.)

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Yerboogieman (author)gmoon2008-02-18

what would be more efficient?

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gmoon (author)Yerboogieman2008-02-18

-- Switching regulators are much more efficient, but expensive.

-- LDO regulators aren't as efficient as switching regs, but you can use a lower input voltage (7.5V or 6V perhaps, 4 or 5 AA cells will last much longer than a 9V batt.) Lower input voltage leads to less power loss (in dropping the input voltage to the output voltage.)

For any approach--if you don't have enough current capacity on the input side, you certainly can't get more on the output (in fact less is guaranteed.) So think about it-- regardless of the the # of regulators, is the battery (or batteries) sufficient to supply what's needed? If not, then two regulators isn't really going to help...

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Yerboogieman (author)gmoon2008-02-19

hmm, i saw switching regulators at radioshack so i think i might go with those but would AAA battery's work? i want it to fit inside an altoids can, and sell them at school

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gmoon (author)Yerboogieman2008-02-20

Sure, AAA are fine--better than a 9V, anyway.

Check out the chart on [http://en.wikipedia.org/wiki/Battery_(electricity) wiki for batteries], "Capacity (mAh)" specifically. The AAA have twice the capacity (1250 vs 625 mAh) of a 9V.

You'll need decide how many batteries are needed. Use too low an input voltage and the batteries drain and quickly drop below the Vin minimum of the regulator. Use too high an input voltage, and you're wasting current through heat, which is just as bad (I'd suggest 5 batteries for 7.5V, especially if they are rechargeables.)

Do they make a battery holder for 5 AAA? :P -- I dunno. But they make 'em for 1, 2, 3 and 4 batteries, so some combination...

If you could cram in AA batts, you'd more than double the capacity again.

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Yerboogieman (author)gmoon2008-02-20

yea they make 3 AAA battery holders so i can do 6 batterys

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tech-king (author)gmoon2008-02-18

now i think i get it. the laptop charges off the usb device right?

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Yerboogieman (author)tech-king2008-02-18

the usb device charges off the charger, no laptop involved, or computer.

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tech-king (author)Yerboogieman2008-02-18

ohh. it charges a usb device. okay. now i get it

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guyfrom7up (author)2008-02-16

like make 10 volts? A hgih power usb power can diliver up to 500mA That can diliver u[ to 1A, which is more than you need so you should have no problem (you can even hook up to usb ports in parallel to the end.

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guyfrom7up (author)guyfrom7up2008-02-16

wow for some reason it's orange

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littlechef37 (author)guyfrom7up2008-02-18
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tech-king (author)2008-02-17

could you please re-phrase your request? i dont understand it

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Yerboogieman (author)tech-king2008-02-17

if you check out member GoodAtit's instructables it has portable usb charger 2.0 and he used to have the part with the charger with 2 combined into one. i didnt understand anything when he had it up but now i know more about electronics that i want to make it

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tech-king (author)Yerboogieman2008-02-18

2 chargers? maybe its because i just woke up, but i still dont understand.

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ry25920 (author)2008-02-16

So this only charges the device? What kind of voltages is needed? Also, you didn't specify what kind of input is needed. Is the input water? Or is it a 1900v high voltage pylon? Try to specify more. Good idea though. +1

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