Instructables

Ultimate Portable Power Source: Axim, PSP, and USB all-in-one charger

Picture of Ultimate Portable Power Source: Axim, PSP, and USB all-in-one charger
My first Instructable described how to build a compact power source that could power a Dell Axim PDA off of 8 AA batteries for extended use on long trips. It used a simple 7805 regulator and a few capacitors to filter the power. It could also be used to power a PSP, since both the Axim and PSP have the same adapter port and use the same voltage.

However, when I finally got to go on a long trip, my friend asked to borrow my charger for his PSP but accidentally hooked the connector up to the 8AA pack backwards. This pretty much fried the 7805 chip, rendering the whole thing completely and totally useless. Although I didn't get to watch movies on my PDA coming home, this led me to create a new design, one that would:

A) Protect against backwards connections so that simple accidents such as this wouldn't damage it
B) Provide power for USB charging devices (like the iPod, Sansa, etc) in addition to PDA/PSP
C) Provide 2A of power instead of 1A, my PDA running on full speed/brightness with WiFi and Bluetooth on apparently used more than 1A (7805 = 5v at 1A) and it would stop charging

To do this, I decided to add a diode at the beginning of the circuit (diodes only allow power to flow in one direction, preventing the backwards flow that destroyed my previous model). To accommodate 2A instead of just 1, I added a second 7805 chip in parallel with the first one. Since each chip provides 1A, 2 of them provide 2A. I also pulled some USB connectors off of a dead USB hub and added one to the circuit so that I could plug iPod/Sansa/other USB charging devices into it and charge them on the go.
 
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wat if i use a 12v gaston battery or a 9v battery????
aekara3 years ago
can i use this to charge a nintendo dsi? please answer my question !!!!

thanks
CalcProgrammer1 (author)  aekara3 years ago
I think the DS handhelds use 5V to charge, so yeah this would work, but the only way to get a DS charging plug is to cut it off of a DS power brick. They don't use USB or any other common connector.
o thank and yea there are usb charger for the ds so yea i am going to built it but can you send me a diagram were i can use 4aa rechargable batterys? please!!!
aekara3 years ago
why did you use rechargable batterys and not your "zombie" batterys :P :P :P :P
kbhasi4 years ago
so that's why u used a 9v battery shell instead of shrink tubing....
the wire assembly is too big, right?
CalcProgrammer1 (author)  kbhasi4 years ago
I used the 9V battery shell because I was housing a full PCB with 2 fairly large regulator IC's, a diode, and two capacitors, it would be a bit too big for shrink wrap and I wanted a more durable casing that would protect the PCB a bit more. The metal battery shell also absorbs a bit of heat from the regulators as they do burn off a lot of heat.
Solderguy6 years ago
I have a Sansa View mp3 player that I would like to recharge on the go. I have to plug it into the computer via usb cable and it uses 5 volts at 500 mA. How exactly would I need to modify your charger in order to suit my power needs?
CalcProgrammer1 (author)  Solderguy6 years ago
Not sure, my friend has a Sansa that charges fine using the USB port as is. You MAY need to use resistors on the data lines, check some other Instructables (iPhone/iPod chargers for instance) for the circuit (you can still use the 7805 though, you won't need two of them).
You should be able to solder the two data lines together, and it will give the device acess to draw 500mA. Though going with the resistors is probably safer.
What value would the resistors need to be?
hedgehog374 years ago
Thanks for the great instructable. My Axim is charging allright with your design but the 7805s do indeed get ridiculously hot. I guess, I'll have to put heatsinks on them. Even with 6 AA batteries they still get very hot.
Aren't they wasting too much power?  Is there another way to keep them cooler while using the batteries more efficienty?
imakethings5 years ago
can i use it with 6v power supply?
Will this schematic work, also how much voltage do I need. 

schematic.gif
CalcProgrammer1 (author)  JaredsProjects5 years ago
Yes, all you really need is the 7805 by itself, the capacitors are just for filtering power spikes and the second 7805 is only needed if your device draws a lot of current.  The diode is important as it protects against backwards connections, if you use that design you have to be absolutely sure that nobody will EVER connect the input power supply backwards else the 7805 will be toast.  The most basic "safe" design would be a diode and a 7805, put the diode on the positive input.  The 7805 requires more than 5V to produce 5V but I'm not sure what the low limit is.  It should probably be able to take anywhere from 7V to 20V or so, our robotics team uses a similar regulator with a 24V battery system but we have a heatsink and fans to cool it off (gets ridiculously hot).
Thank you for your quick reply.  I am going to use this with solar so I was going to put diodes in anyway. 

P.S. Robots are awesome, I have experience with the lego mindstorms, but I am fairly new to electronic (that are more complicated than switches, lights, and motors. 

Thanks Again
can you give me a diagram w/o the PSP or PDA charger
For just USB you mean? This isn't the best solution for USB as USB only requires 500mA (half an amp) and this is designed to put out 2 amps. While this will work with USB, the extra regulators will just waste power, burning it off as heat. The simplest thing to do with USB is to use only one 7805 regulator. This will still require over 5 volts for input but is simple. You can also use a switching power supply like the Minty Boost to get USB 5V out of only 2 or 3 batteries.
BC-455 years ago
will these work with 2 9.6 battery or at least 1 ?????
CalcProgrammer1 (author)  BC-455 years ago
You can use anything from like 7.5V to like 20V, best thing to do if you're using 9.6V batteries (2 of them) is to wire them both in parallel, that way it can supply more power (and last longer).
I didnt know doing it in parallel would be better! Thanks a bunch! That should save me a lot of charge time. I've been lining up a 9v and a bunch of AAAs in series for my version.
biggyeyes5 years ago
dude, it's me, and hell it's working now albeit no LEDs xD now I just gotta build a step-up circuit so that I'll only use 2-4 AA/AAAs instead of a bunch of combined batteries. btw, I used a 1uF cap instead of a 0.1uF cap which you recommended to be placed in the last part of the circuit. Will that be alright?
btw, about the battery source. Since I'm using two 7805s, will I need 7.5v*2 (15v) to power both of them up properly or two sets of 7.5V bats in parallel? Because I just reread your previous comments, and I got confused with this since I remember reading somewhere that I need 15V to power both of them up. I'm just studying electrical physics and I know that parallel circuits only change in current but not in voltage. So the two 7805s should still get 7.5v despite the parallel design? I'm really confused, because I got this problem of connecting just one 7.5V battery pack or two in series when the input of the charger is accepts only one connection.
CalcProgrammer1 (author)  biggyeyes5 years ago
No! You need the same voltage, it just eats more power (amps). This means the batteries will drain faster. If you want to do anything, putting batteries in parallel would be better (doesn't increase voltage, just power). Anyways, a step-up is a VERY BAD IDEA for this project, as it consumes much more power than say, the MintyBoost. If it even were able to step up enough power, the batteries would be drained in a matter of minutes. This is a project where you're best off sticking with the big batteries.
biggyeyes6 years ago
dude, hi it's me again. I just finished the circuit --- it looks like the image above. But I have a problem, my PSP doesn't charge. My friend broke my multimeter so I couldn't test it. I think it's the LED that's making it not work. Btw, the circuit I made doesnt have the green LED in the end as the diagram shows. I used a new 9v battery as the power source. Is the LED that's causing the problem? Please help, thanks! I don't wanna remove the led only to find out it's not the problem because the circuit is so small i don't want to resolder all of them again
small.png
CalcProgrammer1 (author)  biggyeyes6 years ago
My circuit doesn't have any LED's... First, a 9V battery will drain REALLY FAST with this circuit. 9V's aren't meant for high current applications (as such, they are usually only found in flashlights, smoke detectors, small radios, etc). It should work, but the battery will die quickly, especially with the 2A system running. You should only need one 100uF capacitor, just put it across the DC input lines (just after the master switch should work). Make sure to line up the positive and negative lines of the capacitor to the positive and negative lines of the input. You don't need any capacitors after the regulators, though you may want to put a 0.1uF at the very end (right before the output to USB/plug). I did in mine, but it really isn't necessary. If you want to use LED's, remember to use resistors with them. I'm not sure what kind you'd need, but LED's usually burn out at 5V if you don't use a resistor in series with it. Also, you don't need two switches on the second regulator, just one at the front of the circuit will do, the second switch after the regulator is unnecessary. Make sure you get the polarity right before connecting to your PSP (make sure the positive and negative lines from the circuit match the ones on the official power brick or adapter). I doubt the LED is the problem, though if you're not using a resistor, the LED may have burned out.
circuit.jpg
ah, thanks man. I'll be trying that when I have more time. But the PSP still won't charge with a fully charged 9v battery running using a single 7805. My old charger (a simple battery>7805>USB circuit) worked. I'll be making it again using your directions but with no LEDs to simplify he circuit. Again, thanks a bunch!
CalcProgrammer1 (author)  biggyeyes6 years ago
You should probably test your 7805's. Just hook them up without any extra stuff (just battery to 7805 to PSP) and make sure it charges. If not, you may have gotten a bad 7805 or accidentally fried it while building the circuit. 7805's are sensitive to reverse-connecting and will break if you hook them up backwards.
biggyeyes6 years ago
Nice I didn't know two 7805s would yield 2A, I thought they would still yield 1A both. Anyway, if I connect a 1A device it would still be ok right? Because right now I have a very simple charger. Battery > 1x7805 > USB Would it be alright if I connect another 7805?
CalcProgrammer1 (author)  biggyeyes6 years ago
It's basic electrical physics. A series circuit increases voltage (two 1.5V batteries in series gives you 3V). However, a parallel circuit increases amperage (current). If one 1.5V battery could provide 500mA, connecting two of them in parallel would still yield 1.5V, but devices could use up to 1A instead of just 500mA (0.5A). You can't wire 7805's in series, though, because they have a dedicated input line meant to be connected to the initial power supply, but connecting the outputs of two 7805's together will double the current, yielding 2A. Current is an availability thing, a device that uses 250mA will only use 250mA no matter if it's connected to a 250mA power supply or a 5A power supply. The extra power will only be utilized by devices that need it. Voltage doesn't act this way (putting 12V through a 5V device will certainly fry it) but current does, so don't worry about higher amperage. However, USB is only 500mA. Connecting another 7805 will only make the battery pack die faster (7805's aren't 100% efficient, they actually consume a lot of energy just to convert, so using 2 7805's is half as efficient as using just one, I did it because I had to, but otherwise 1 is recommended). If you're just charging 1 or 2 devices at a time, then 1 7805 will do, if you plan on making a USB charger to charge 3 or more devices, you may want to use 2 chips. You could also put a switch on the input line of the second 7805 to turn it off when you're not running under full load (saves power because the second 7805 won't be drawing any power).
Ah, nice to know :D Haven't finished physics yet, still in projectiles, torque and everything. I was thinking of 2A or 3A because my PSP won't really charge properly with just 1x 7805. My PSP's charger gives 5V at 2800mA (2.8A). That means that my PSP is only receiving 35.71% of what the A is supposed to be. And by the way, just to make things clear, is the diagram correct? I didn't put the capacitors and crap in.
instructables_seriesquestiondiagram.png
CalcProgrammer1 (author)  biggyeyes6 years ago
Yeah, that's right. The parallel circuit is correct. If you were to try 3 of them, you would add another one in parallel. With three of them it may get really hot, so you may want to consider some sort of heat sink, and you'll probably want a larger battery pack (or maybe a battery pack that uses like 12AA's with two sets of 6 in parallel, as parallel will increase runtime).
Gonna build one now. Thanks a bunch!
couldnt i jst take an ipod cord , cut it in half and feed the 12v battery cords and solder them then tape them together and plug it into my ipod?
CalcProgrammer1 (author)  Thundertydus6 years ago
No, cause iPod (and anything else USB) uses 5 volts. Feeding 12V directly into your iPod would fry the charging circuit and render it totally useless. The regulator circuit makes 8 to 18 volts or so into a steady 5 volt supply.
Unless the iPod is a FireWire one or the cable is firewire xD (read it somewhere here in instructables)
Diskun6 years ago
AWESOME! Just what I needed. But I could use some tweaking. I want to plug this power pack to a HTC Diamond PDA/Phone, the wall charger output is 5V @ 1A (battery is 900mAh, so I think I don't need two voltage regulators or 8 batteries. 4 of them and just 1 IC, and the whole thing would fit into a black project case I have around here. Much more portable and fancy :P So here's the big question: - Which modifications would I have to do to the circuit? Thank you so much p.s. Is it possible to integrate a quick battery charger to get an all-in-one portable power pack?
CalcProgrammer1 (author)  Diskun6 years ago
Simply remove the second 7805 chip. You'll only get 1A out of it, but most smartphones these days aren't as complicated as the Axim and don't need as much power. You'll need to find the right kind of plug for your phone, but other than that, just use the circuit described here.

However, I use 8AA batteries because it puts the voltage high. 4 might not be enough to make the regulator work properly, as 4*1.2=4.8 (too low to regulate, but enough to power your device without a regulator) and 4*1.5 (alkaline) = 6 (too low to regulate, but too high to use without a regulator). I would suggest at least 6 batteries to make the 7805 function properly.

Just remember the diode and you'll be good, the capacitors are filtering components, but since batteries have a fairly stable output, they really aren't totally necessary. I put them in just to be sure.
Nice. So... using more 2100mah @ 1.2V batteries will make any difference in stamina? I guess they do, but I'm not sure if it has something to do with the 7805. Excuse me if I sound stupid, I'm not too much into the theory, but I enjoy playing around with my soldering iron and some wires :P
CalcProgrammer1 (author)  Diskun6 years ago
If we assume that the voltage drop in batteries stays constant (the time that 1 battery takes to go from 1.2 volts down to nothing), then yes, more batteries should mean longer runtime, as the voltage going into the circuit will stay above 8 volts (the minimum input that the 7805 can make 12V from) longer. A better design would be to use like 9V supplies in parallel rather than a bunch of batteries in series, but this was easier to get and use.
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