I have a camera that uses 2 AA batteries that appear to be in series (standard one up, one down, with a little metal tab bridging one end in the battery compartment - 3V DC, right?). It does not have a DC input.
Supposing I want to be able to “create” a DC-IN connection so that if my camera is being used indoors, I don’t have to change batteries every 20 minutes.
Would it work to connect the output from a suitable AC/DC adapter to the terminal connections inside the battery compartment?
I can’t see why this wouldn’t work, yet I’ve never seen an AC/DC adapter designed to be used in this way, E.G. with dummy batteries or somthing like that. . .
Just wondering. Are you using standard alkaline batteries or NIMH batteries? I don’t care what camera you’re using, but NIMH’s should last longer then 20 minutes even if you use it in video mode.
AA battery eliminator. This particular unit will work with any device using 1 to 4 AA cells, and with an output of up to 1 A, it should power most digital cameras. There are probably others which can supply higher current levels.
I didn’t notice that one is for 12 VDC operation in a car or boat. You’ll want an AC version, which I can’t find at the moment. It wouldn’t be terribly hard to make one. 1 A is probably sufficient current, but I’d go for 2 or 3 A, just to be sure.
Probably because battery compartments usually don’t have convenient holes for the wires. I can’t think of any other reason it won’t work.
You should use a high-quality AC adapter though. I once used a cheap “universal” AC adapter (the kind that has selector switches for voltage and comes with many different connectors) on a digital camera and it resulted in a lot of image noise.
But are you sure your camera doesn’t have DC input? Perhaps it can work off the USB power?
Excellent point. If I were designing such a thing I’d either include a large series inductance or a large parallel capacitance to reduce the ripple that “wall wart” type adaptors often put out.
Probably not. USB 1.x is limited to 100 mA and USB 2.0 is limited to 500 mA, unless used with a powered hub. Not that it’s impossible, but I’ve never encountered a digital camera which could be fully operated on USB power.
In series with the load, sure. It’s not terribly common, since at 60 Hz, it requires a fairly large inductance value to be effictive which generally either means large physical size or relatively high DCR–one is a tradeoff of the other, and likely a higher cost than capacitive filtering. But, it’s perfectly safe design. In combination with parallel capacitors, a series inductance can provide a much sharper ripple cutoff than either alone, in fact. It functions as a low-pass LC filter.
Harmonix - 20 minutes was a bit of an exaggeration; actually, I’m kind of happy that this camera seems to go longer on 2 AAs than my last one did on 4. I’ll more than likely get some NiMH’s at some point.
The real point of my question is why things like Q.E.D.'s battery eliminator don’t exist (or are not that common). Naturally, the physical design of battery compartments presents a problem, but beyond that I wasn’t sure if something at the electrical level would prevent it. With my limited knowledge, I couldn’t think of anything, but IANAElectricalEngineer so I thought I’d check.
astro - Cheap-o Polaroid PDC 4055. . .
scr4 and Q.E.D. - thanks for all the good mind-fodder. I’d have never thought about the noise a standard cheap-o adapter’d put out. Still, It’s good to get confirmation that conceptually it’d work.
As for USB options - I’d say not. This is a pretty basic camera, and the USB seems to be there just for file off-load. . .
Thanks again for all the information - I really appreciate it.
Slight (but related) highjack: Would it be possible to create a parallel series in order to provide the proper voltage but with a larger amperage?
For example, my little MP3 currently contains a single lithium AAA battery that provides 1.5v and probably something like 1000mAh or whatever those Energizer Lithiums are supposed to provide. If I run two AAAs in parallel I should be able to effectively double the amperage, thus doubling the life, correct?
Now, would this work in a series circuit? Say, four AA batteries in parallel oriented positive to negative, and four AA batteries in parallel oriented negative to positive, with the positive and negative terminals on the device connecting in series to the first of each parallel array?
In theory, putting batteries in parallel will increase the total amp-hour capacity, however, in practice this generally isn’t a good idea. The problem occurs when one cell discharges more rapidly than the others; unless they all have exactly identical internal resistance characteristics, this will happen. At this point, there is a voltage differential between the cells, and the “stronger” ones will try to push current backwards through the weaker ones. This heats up the weaker cells, which in an extreme case, could lead to bursting–which is not only messy, but also unsafe. If you absolutley must, well, go ahead and try it. But, if you’re going to have an extra cell outside the unit anyway, you’d just be better off to use a single C or D cell, instead. This will also give you a higher capacity, but without the potential problems or parallel cells.
I’ve got this mental image of a D-Cell strapped with electrical tape to one of the ultra-small format MP3 players, looking like nothing so much as a small package of dynamite complete with digital timer. . .
Okay, nobody move! I have a bomb! A Sex Bomb! And nobody wants fifty hours of Tom Jones!
Er, but seriously. If you were to take two brand new AAA cells, strap them together in parallel and hook the end one up to the player, theoretically you should have the same resistance in both cells, so the risk would be fairly minimal, wouldn’t it? Especially since my player dies long before the battery meter reaches half. (It’s cheap, okay?)
I could rig up an AA, but change one AA rigged to make proper contact with the terminals would be more of a pain than just duct taping two AAAs together and shoving one of them in and having the other stick out.
Sure, again in theory. It’s just not a good design practice for the most part, which is why you almost never see products designed to use batteries in parallel. At low currents and low voltages, such as your MP3 player, the risk is, I agree, very minimal. I just didn’t want you thinking it was a completely risk-free practice for any given application.
Well, no, since more batteries you run in parallel the greater the risk that one of them is a bit off and could spoil everyone’s fun. But for units that normally use one or two cells the the risk should be pretty minimal as long as you’re using good quality batteries and they are all brand new when connected.
Not that it’s really a practical solution by any means, but if for some reason you really need to go a longer period of time between battery changes/recharges it’s an acceptable hack job.
