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Powering device with batteries

Discussion in 'Power Electronics' started by steebu, Dec 10, 2012.

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  1. steebu

    steebu

    4
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    Dec 10, 2012
    Hi all,

    don't have much of an electronics background, but have a project at work that I would like to simplify.

    We have various reference cameras on our stage, and instead of running long HDMI cables back to the recorder we are using these nifty HDMI over Ethernet converter/extenders:

    http://www.amazon.com/Monoprice-Ethernet-Extender-Cat5e-Cable/dp/B007YIV1DQ

    So from various points on our stage, we have a power cable running some 50 feet to a power strip, into which our camera and this extender are plugged. We also have a 50 foot ethernet cable running to the extender.

    In order to minimize mess, we'd like to do away with the power cable. The cameras have their own battery and have decent life ( we can always purchase more batteries - they're just off-the-shelf Canon cameras).

    That leaves the extender.

    I'm wondering if we can't power that with a bunch of AA batteries or something. I have no idea how much power they draw (I can't imagine it's much?), but I noted some numbers on the back of the transformer:

    100-200 V
    50/60 Hz
    Ouput 5V
    2000 mA

    I have no idea what any of that really means ... but what I really need to know is, "Is there some battery pack thingy that I could plug four double-A rechargeable batteries into that can power these extenders?"
     
  2. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    It depends on how long you want to power the device for. If you want to use AA's then you can't get exactly 5 volts, you can either get 4.5 or 6. I would recommend 4.5 as batteries actually start a bit above what they are rated, so you will be peeking at around 5 volts.

    Lets say you use 3 AA's wired in series as to increase the voltage to 4.5, if you don't understand series and parallel wiring take a look at this site: http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel

    The problem is that 1 AA is capable of providing 2500 ma hours so you would only be able to run it for 1 and a half hours with 3 batteries.

    If you wanted more run time you can double the amount of batteries and wire them in both series and parallel to get 4.5 volts that will last for 3 hours. But that would use 6 batteries!!!

    This begins to get impractical and expensive very fast if you need any decent run times; so I would recommend just sticking with the power cord unless your run times are short.
     
  3. BobK

    BobK

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    1,686
    Jan 5, 2010
    3 or 4 D cells would get you about 6 hours of operation, if that is helpful.

    Bob
     
  4. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    But that is still going to cost a lot even using larger cells. If you could tell us how long you hope to have them operating that would be great.

    Another possibility would be a rechargeable battery pack; but in order to find a type that might work for you, we still need to know how long you want to run it in a day.
     
  5. steebu

    steebu

    4
    0
    Dec 10, 2012
    Hi all,

    thanks so much for the replies.

    Typically a shoot day is around 8 hours - we'd be shooting from 9-12, break for lunch, then shoot again from 1-5.

    I totally don't mind changing out batteries; we could do it during breaks. There typically isn't a constant flow of recording. Basically, imagine it as a movie set, where between shots we could change out the batteries. If the batteries were able to power the devices for 3-4 hours at a time that'd be fine. I imagine we'd have a charger array where we could grab 4 D's at a time (or AA's, or C's, or whatever), plug them in, and re-charge the others.

    Is there such a pre-made device? You pop in four batteries and it has a standard 2-prong plug where you plug in your device and get juice? I took e-mag 20 years ago in college, so while I'm familiar with series vs. parallel, I don't remember any specifics. Hey, I'm a computer scientist, not an electrical engineer. :)


    steve
     
  6. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    Based on what you have said, I think your best bet would be to use Tenergy D cells as they hold a lot of ma (10,000 each) and just work great. You could use 6 batteries per converter/extender and that would ideally give you 10 hours. Aside from batteries, you should also slap a 5v regulator on each circuit so you don't break any of the converters by giving them to much juice. Finally you will need a charger;

    the charger can be bought with 8 D batteries on amazon for $100:

    http://www.amazon.com/Tenergy-Unive...able-Batteries/dp/B002FKZEJU/ref=pd_sbs_hpc_5

    But that charger can only charge 4 at a time and it is expensive, I don't have time right know but I will do some more searching tomorrow and hopefully I will find something that will work for you.

    The batteries by them selves can be bought here for $50:

    http://www.amazon.com/Tenergy-000mA...e-Batteries/dp/B001AYIRH8/ref=pd_bxgy_e_img_y

    Like I said i will do some more searching later and let you know what I find.
     
  7. Dude22

    Dude22

    66
    1
    Mar 30, 2012
  8. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
  9. steebu

    steebu

    4
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    Dec 10, 2012
    Great, I'll take a look at both sites.

    Would something like this work?

    http://www.officedepot.com/a/products/839497/Lenmar-PPW66-Lithium-Polymer-External-Battery/

    along with this?

    http://www.robotshop.com/barrel-jac...ource=google&utm_medium=base&utm_campaign=jos

    It looks like the plug on the extender is a 2.1mm barrel jack (eyeballed it using a tape measure).

    The battery from office depot is 5V and has a 6600mAh capacity.

    EDIT: Ah, KJ6EAD, that looks like a higher capacity version of what I just posted. Since this is for work, we can totally afford a few of those. I think the USB->2.1mm jack converter is all we'd need at that point?
     
    Last edited: Dec 10, 2012
  10. Dude22

    Dude22

    66
    1
    Mar 30, 2012
     
  11. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    take a look at what KJ6EAD said as it is a valid point, if you can afford it the system he recommended would be GREAT.
     
  12. steebu

    steebu

    4
    0
    Dec 10, 2012
     
  13. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    The MP3500 comes with some barrel plug adapters but it's not hard to make your own. If I remember right, they connect via a 3-pin mini-DIN connector. There's also an industrial version that's harder to change output voltages on (a safety/anti-idiocy feature).

    By the way, that 2A current rating is a maximum capacity rating for your existing power supply. The actual consumption of the extender will certainly be far less.
     
    Last edited: Dec 10, 2012
  14. BobK

    BobK

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    1,686
    Jan 5, 2010
    It better be:

    I worry that this is a very expensive solution that might not work at all.

    Bob
     
    Last edited: Dec 11, 2012
  15. KJ6EAD

    KJ6EAD

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    158
    Aug 13, 2011
    Thanks for pointing that out Bob. Here's what I found for the extender:
    Source: http://www.monoprice.com/mobile/Pro...d=109&categoryId=10110&subCategoryId=1011012#

    There's no problem with the rate; 5W consumption vs 7.5W continuous DC-DC converter capacity. Using the 5W consumption figure and the [email protected] battery capacity, the minimum run time should be 8.6 hours.
     
    Last edited: Dec 11, 2012
  16. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Okay, then it should be fine.

    Bob
     
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