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Express your silicon love, hate and curiosity
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| need someone who knows electronics in portables. |
Master_Scythe
25/8/05 7:15:41 PM
Champion
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I have an Axim X50v PDA. Now one big topic discussed over at aximsite, is portable chargers, and how to use em. Now, none of us are CERTAIN of our skills in providing such portable power.
My bretheren here at Atomic are the only community i thought i may be able to find someone who specialises in electronics to tell us for certain if this is cool.
http://www.aximsite.com/boards/showthread.php?t=95428&page=1&pp=25
have a read (if its broken, forums > X50 forums > accessories)
we need to know is thats safe to do FOR CERTAIN. just reply here and i'll relay.
Thanks mates.
Scythe. -----
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IvanTheTerrible
25/8/05 7:54:44 PM
Banned
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I've done a similar thing with my digital camera. No electronics involved. -----
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merlin13
26/8/05 11:08:15 AM
Guru
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And if you'd be using this thing on a regular basis and you were really sly you'd also consider using rechargable batteries and drop a small charge circuit of appropriate configuration for them in there as well... -----
Anything not nailed down is mine, and anything I can prise up is not nailed down...
Carpe Jugulum.
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Master_Scythe
28/8/05 1:41:55 PM
Champion
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yeah. but is that all good though? that design OK? it'll work and be safe?
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merlin13
29/8/05 4:03:00 PM
Guru
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It's on the Web, of course it's safe... :]
Yes it'll work, assuming you either amputate or make damned sure you don't use the the car charger plug - 9 volt batteries have a history of getting very angry if you try and stuff 13.8 volts or so back into them the wrong way.
All this thing is doing is sticking 9 volts in place of the nominal 12 volts for the car charger (and the three 9 volt batteries would be in parallel as I rather doubt the PDA would be running on a 27 volt internal battery...).
So if there's no voltage conversion bits in the charger then obviously the PDA can handle up to 12 volts on the supply input (well, 13.8 nominal if you want to get technical).
Have a look at your wall charger to see what volts come out of that (Mr Multimeter if in doubt), that'll also give you an idea what sorta battery voltages you could use. -----
Anything not nailed down is mine, and anything I can prise up is not nailed down...
Carpe Jugulum.
Carpe Scrotum.
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stadl
29/8/05 4:45:02 PM
Hero
Guru
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What they are doing on that site is probably pretty safe.
Just beware it appears even the guy who did it originally doesn't really understand what he has done. The photos he's shown don't match up with what he describes in the text: Series vs parallel connection of the batteries. And the discussions of solving voltage surges from batteries with a fuse is just weird.
Basically, they are buying a cheap DC-DC voltage converter usually designed to convert 12 or 13.8V from a cigarette lighter socket down to the 5 or 5.4 V that the PDA needs.
They are disconnecting the lighter socket bits and replacing them with battery connectors.
These DC-DC converters usually contain a cheapo single IC and a few components to make a switched mode power supply and shouldn't be much of a problem. They are typically good for anything from about 9V to 15V. Probably all ok for normal 9V batteries, but be careful, many rechargeable "9V" cells are actually a bit less (around 7-8V) and may not be sufficient for the DC-DC converter - depending on it's design.
The reason for 3 9V batteries in parallel (yes they are in parallel, loook at his photo, all the red wired are connected, and all the back wires are connected) is simply to give more current. This basically equates to extended life. 9V batteries are notoriously low current and capacity (afterall, it's actually 6 small 1.5V batteries stacked together inside - they range from about 200 to 600mAH). You'd get much higher capacity packaging 6x 1.5V AA alkaline batteries, or 8x 1.2V AA NiCD/NiMH rechargeables, and not have much more weight. but have several times the battery life (up to 2500mAH). Even 6xAAA will have more capacity, and possibly be cheaper to boot. -----
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Master_Scythe
30/8/05 9:28:19 AM
Champion
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Stadl and merlin. legends :D.
the PDA charger gives 5.4v.
Heres my question stadl; how do i make AA's go parallel? the connectors you buy from dick smith and such all go in a series and have a single output. is there a holder that goes parallel too from them? or is there a way to fix that. also; a AA doersnt have the voltage does it? or are you suggesting i DO use them in series to give voltage, and just make sure i dont use more than say 12 AA's (as if) so i dont kill the car charger thing? -----
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stadl
30/8/05 12:50:11 PM
Hero
Guru
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You want the AAs to go series. in that case, because you want the 1.2-1.5 V cells to add up to around 9V.
Batteries in series add voltage.
Batteries in parallel add current/capacity.
The difficuly is determining what the PDA can cope with. While it's standard charger may provide 5.4 V, that doesn't mean it's the only thing it can take. It may be fine with only 5V, and it may be able to take 6V without problems. If that's the case, you could feed 4x 1.5V alkalines, or 5x 1.2V rechargeables in series directly to it.
The advantage of using the car adapter is that you can supply more and let it convert to the safe voltage. It also means that if your batteries drop a little in voltage, the PDA won't see that as the DC-DC converter will keep pumping the required voltage. the converters (or it may be only a simple regulator on second thought) require some head room of course, so you'll probably need to provide it with around 8.5 to 9 volts or more for it to be able to output 5.4V That's probably 6 Alkaline AAs (1.5V each) or 8 rechargeables (1.2V each) in series. -----
...so brilliant in fact, that by simply harnessing the power of one live frog, it.. it.. uhh.<poke> <poke>
World domination has encountered a momentary setback. Talk amongst yourselves.
Waffles, Lots of Waffles... And Chips...
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Master_Scythe
30/8/05 8:44:20 PM
Champion
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so.... i could run 6 AA's in a series....
so if i understand correctly, i could run 2 lots of series'd 6X AA's?
so AA's X6 in one holder, AA's X6 in another holder, and just gain usage time.
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stadl
30/8/05 9:21:36 PM
Hero
Guru
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Yep, And you could wire the 2 sets in parallel, but not my preference.
If it was me, since the PDA has internal batteries, it won't die immediately, and you can afford to disconnect the external pack. Just use them as two separate sets and swap them over when they get low, that way you have two weight options based on how long a life you need. But you have a battery pack on your belt that is half the size, and the other half might get to live in your backpack or elsewhere.
Because if you wire them in parallel, you'll have to make sure that the two sets are always at the same charge, or the stronger set will be trying to charge the weaker set rather than run the PDA.
With separate sets, you can be charging one while using the other. -----
...so brilliant in fact, that by simply harnessing the power of one live frog, it.. it.. uhh.<poke> <poke>
World domination has encountered a momentary setback. Talk amongst yourselves.
Waffles, Lots of Waffles... And Chips...
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Master_Scythe
31/8/05 7:48:41 PM
Champion
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Stadl, theres a reason ur 'hero' and im still deciding how i want to try to get there.
ideas like that are what makes it. thank you.
Now i know its safe because the charger is limiting it, i know what a series vs parallel is properly, and u gave me some wicked ideas. +1 to.... whatever you got goin for ya. lol.
thanks. will be buying a $15 PSP charger and moddin away! -----
Stargate Rules!
A64 3500+, ASUS A8N-SLI-Deluxe, Leadtek 6600GT, 1gb Corsair TwinX PRO, 200GB WD SATA, 36GB SATA RAPTOR, 109 DVD, LG DVD-rom. Logi MX Duo.
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