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Simple project

Discussion in 'General Electronics Discussion' started by Diar, Sep 28, 2014.

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  1. Diar

    Diar

    12
    1
    Jul 27, 2014
    Hey guys so I'm looking to extend a little project I've been working on, I'm currently building a small coffee table which I plan to attach two perspex sheets to the top sandwiching a number photos etc.
    I'm looking to extend the idea and add some LEDs to the table to light the table from the inside out so to speak, I don't want it connected to the mains though.
    I've been looking at a lot of RGBW LED strips and things on amazon, with the dim-able remote controls and the like but I cant find any that come battery operated and I don't want to knock something up myself and find that I either burn the house down or find myself changing batteries every 2 days. I don't want it lit all day and night, only a few hours in the evening as a bit of room/mood lighting.
    Anybody out there have any ideas or similar projects that they've seen/worked on. Any help is much appreciated!
     
  2. Diar

    Diar

    12
    1
    Jul 27, 2014
    For such a simple project I'm surprised nobody has replied. All I'm looking is a bit of information on LED edge lit applications like how long I can run off a battery source. Ive trawled the internet looking for solutions and i either have run a golf cart battery and get 65 hours of juice but nothing on how many LED's are in the chain for those sorts of running times. Has anyone any idea if this is worth pursuing or for the running times I will get out of batteries isn't worth the effort in researching it.
     
  3. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    In order to determine run time, you will need to determine the power requirement for the LEDs you want to run.
    LEDs commonly draw 20-50mA per color, and the more you have, the faster your battery will die.

    To be fair, you did ask for someone who has done something similar... not for someone who has any ideas ;)


    Step one, mock-up your design to determine LED counts.
    Step two, find or design a constant current driver for your LEDs.
    Step three, grab enough batteries to power your lighting for the desired period.

    You can do this in reverse as well... by finding a battery first, then see how many LEDs you can power with it.
     
  4. Diar

    Diar

    12
    1
    Jul 27, 2014
    Thanks Gryd, Yea sorry i did ask for somebody who has done similar. That's my bad! Thanks for the reply.
    Ive looked at a few of the cheap strips off amazon (my housemate a few years ago put some up around his bedroom as his room lighting and they did a decent job), as far as I can determine they run off a 12V mains supply so in theory they can be converted to battery. My knowledge on this topic is minimal to none. Have you any experience in LEDs and how many it would take to effectively light the edges of a table?
    My budget is almost non-existant so ideally if I can figure out the chances of it working before I start buying things it would be great!

    edit --

    Ok here's an example:
    http://www.amazon.co.uk/XCSOURCE®-Waterproof-Changing-Controller-Decoration/dp/B009WKRLOC

    According to the data on this listing, the working current is 0.4A.
    If I run this off a pack of duracel powercell AA batteries at 2.7Ah does that mean i can roughly run the leds for approximatly 6.5 hours?

    Would those figures be based off 1 LED and 1 Battery or how much does it change? In theory I only need a meter of LED strip.
     
    Last edited: Oct 6, 2014
  5. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    OK well, you can easily convert voltage or amps with an extra piece of hardware.
    And yes, that 0.4Amps is the number we need, but it is per meter.

    I honestly think the best option for you, would be to get your hands on a 12V battery, or some RC car batteries as they have a charger and will be much cheaper than packing it with disposable batteries.
    Take a look at 12V Sealed Lead Acid batteries for house alarms or motorcycles as an option other than RC battery packs.
    The 2.7Ah battery pack in theory would run one meter of LED strip for 6.5Hours, but only IF the battery back was 12V as well.

    I cannot reliably tell you how many leds to use, but tracing the perimeter with strip light is a good way to eliminate guess work. There are plenty of LEDs there (perhaps a little bit too much), but you don't have to wire one from scratch, so I'd say it's a great trade-off.
     
  6. Diar

    Diar

    12
    1
    Jul 27, 2014
    How would a 12V Lithium ion battery do in place of the RC or Lead Acid batteries? I think the Lead Acid batteries are a bit bulky and difficult to conceal for what it will be used in, also it will be used in a coffee table and wouldn't be as ventilated as recommended. I have found relatively cheap lithium ion batteries at 12V and 6800mAh.
     
  7. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    That would work just fine. I didn't bring it up due to some of the charging requirements they have.
    This can easily be resolved by buying a small lithium charger (They can be about the size of a quarter).

    Keep in mind that lithium batteries are typically about 3.7V per cell, so a 12V lithium battery would have multiple cells in it.
     
  8. Diar

    Diar

    12
    1
    Jul 27, 2014
    Just read up on some of those charging requirements, yea those are a bit of a turn off. Ill keep you posted on progress as I acquire the time and parts needed to put it all together. Really appreciate your help!
     
  9. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Not a problem.
    Those charging requirements could be easily forgotten about if you buy a charge controller for it though and build it into the table. The controller may be able to double as a battery monitor to prevent over-discharging the battery. (You could have a small DC barrel plug in the table to charge it)
    I am not sure how much space you have to play with though ;)
     
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