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Lots of Miniature Lamps in Parallel to a Battery

Discussion in 'Power Electronics' started by icecapsule, May 4, 2013.

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  1. icecapsule

    icecapsule

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    May 2, 2013
    Hi, I want to wire quite a lot of lamps in parallel to a battery and I was wondering how many could I have in one set? And what battery would I use?

    So, I want to wire as many of these as possible;
    Panel Lamps 15x29mm E10
    15mm x 29mm 2.4V 625MA 1.5W E10

    There are lots of other ones in this range that would also be suitable that go from 2.4V (this ones the lowest) to 60V, with the MA and W changing accordingly- so if it's easier to use an alternative bulb let me know, I got the bulb spec from http://www.lampspecs.co.uk under Miniature Lamps.

    Much like fairy lights I suppose, but they have to be these bulb types :) (I've chosen this bulb type for the aesthetics, and this particular one as it's the lowest in the range)

    (just to note: I previously put this Thread up asking to wire to the Mains, but the advice of fellow forumers meant I could have 100s of these bulbs to the Mains I figured it's maybe best for all concerned (and health and safety!) to wire it up to a battery. As I think I'd get more of these wired to a battery than I originally thought.)

    Thanks!

    Claire
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
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    Nov 17, 2011
    A 1.5W lamp requires 0.625A at 2.4V.
    Let's assume you have a 2.4V battery (2*1.2V NimH or NiCd in series).
    Let's further assume you have N lamps. Wired in parallel the current consumption will be N*0.625A. You're talking N=100 or so, that means 62.5A of current. You will need very thick wires and very big batteries to sustain that current for any time. I don't think this approach is good.

    With 100 lamps I suggest you look into LEDs. These are much more efficient and operate at much lower power.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
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    Jan 21, 2010
    It sounds like you really want the bulbs due to an asthetic reason.

    OK, if so you'll have to live with the fact that 100 of them is going to be a lot of power. That means either a high (dangerous) voltage and a lowish current or a low voltage and a high current.

    I would recommend that you use the highest voltage consistent with safety that you can. That may be 48 volts. 48 volt power supplies are pretty easy to find.

    The next thing is to determine the wattage of each bulb. The question is, are these for effect, or for lighting?

    If they're for lighting, calculate the amount of light you need (roughly) and divide this by 100. Get bulbs with a wattage near that.

    If it's for effect, look for the lowest wattage bulb you can find (consistent with the effect you're after).

    If it's for lighting, and you choose a 12V 1W lamp (presumably you want close to 100W of lighting) then connect these in strings of 4, and have 25 strings of these in parallel. Your 24V power supply will need to provide a little over 4A, but Id get one rated for 8A because the lamps will draw a lot more power as they turn on.

    If it's for effect, I would take my bulbs, perhaps I have found some 6V 0.25W lamps which give me the effect I'm after. The next step is to see if I can run them from a lower voltage. Perhaps I find that I get a nice effect at 4.5V. That means each string is 48/4.5 = 10.7 lamps. 10 lamps per string works out well for my 100 lamps, so I connect up ten strings of ten bulbs.

    In this case the total power will be less than 0.25*100 because the bulbs are being run from a lower voltage (you could measure 1 string to see what it is and multiply that by 10). Again, choose a power supply capable of at least twice the required current.

    The advantage of running bulbs at a lower voltage is that they will last a lot longer. This allows you to have longer strings. However, it is best to keep the strings relatively short as a single blown bulb will turn off an entire string. This will both affect your display more, and make finding the broken bulb harder as the length of the string increases.

    A friend of a friend is building a display using bulbs like these. He found they work nicely from something like 30V (for his needs) from memory. He will be switching them on and of rapidly using large contactors. (Yes, it's for fun) We observed it made a marvelous percussive musical instrument :D
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
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