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Help with power supply for pinball machine

Discussion in 'Power Electronics' started by jibmums, Aug 6, 2013.

  1. jibmums

    jibmums

    4
    0
    Aug 6, 2013
    Actually it's not an entire pinball machine, just the top part. Here's my project: I have the entire top of a Bally Playboy pinball machine, the part that has the glass that lights up. The main table is long gone.

    The glass is lit up from behind by twenty-nine #44 bulbs, which are 6.3V .25A. I want to connect a power supply to the parallel wiring that connects all the bulbs, so this thing will be a lit-up display in my mancave.

    However, I know absolutely nothing about electrical/electronic stuff. I was hoping to be able to use one of the many wallwarts I have leftover from old dc players, radios, etc., clip the end and solder it to the wiring They all have similar input ratings, 100-240V and similar amp and Hz ratings. Each has a slightly different output though; usually 12VDC & 2A, some 5V & 1A.

    I'd like to know if it's possible to use one of these for my purpose? If not, can you point me to a Radio Shack unit? Also, most importantly, why that particular power source? In other words, is there a formula, given the specs of the #44 bulb above, to determine what kind of output I would need to power 29 of them?

    I may be fitting this with LEDs instead of the #44 bulbs in the future, so I'd like to be able to figure out on my own what power source to use. Those are 6.3V and 40mA. Would I be able to use the same source as for the #44's, or do I need something less powerful?

    Of course, safety is an issue and I don't want a power source that will overheat if I leave this on for a few hours. Thanks in advance for the help guys.
     
    Last edited: Aug 6, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,223
    2,696
    Jan 21, 2010
    The 5V 1A power supply could run 4 bulbs in parallel.

    The 12V 2A supply can run 16 bulbs. You need to connect pairs of bulbs in series and then connect 8 of these pairs in parallel.

    parallel means like a ladder -- with the bulbs being the rungs between the power supply rails.

    Code:
    +ve ---+---+---+
           |   |   |
           O   O   O
           |   |   |
    -ve ---+---+---+
    
    Series means connected in a line like a whole lot of people walking hand in hand -- the people are the bulbs and the power supply is connected to the extreme ends of the line

    Code:
    +ve ---O---O---O--- -ve
    
    The "O"'s are the bulbs.

    series parallel is like this:

    Code:
    +ve ---+---+---+
           |   |   |
           O   O   O
           |   |   |
           O   O   O
           |   |   |
    -ve ---+---+---+
    
    That last one is three strings of two bulbs.

    The strings are in series, then three sets of these are placed in parallel (in your case it would be 8 strings of 2 for the 12V 2A power supply).
     
  3. jibmums

    jibmums

    4
    0
    Aug 6, 2013
    If it's any help, here's a photo of the back of the light panel, showing the wiring. The bulbs I want lit up are circled in yellow. The bulbs circled in green are "controlled lighting" and won't be lit. The 29 bulbs are already connected in parallel (I think), what would I need to use to power them without adding additional wiring?

    [​IMG]
     
    Last edited: Aug 6, 2013
  4. KJ6EAD

    KJ6EAD

    1,114
    157
    Aug 13, 2011
    You can use a 6.3V 10A power transformer to drive the bulbs with AC. This is cheaper than an AC to DC supply and better for bulb life (DC notches the bulb filaments). I recommend fusing the secondary (output) at 10A (you should be using 7.5 normally) and the primary (input) at 500mA.

    http://www.digikey.com/product-sear...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

    To answer your questions about the math: 29 X 0.25A = 7.25A and 29 X 0.04A = 1.16A. The product linked below doesn't list specifications but may draw as much as 0.075A X 29 = 2.175A

    http://www.centsibleamusements.com/pinball-led-44-47.aspx

    The transformer (AC supply) could be used for the LED replacements but as you can see from the math above, the LEDs require far less current so retrofitting the bulbs now could save you a lot on the power supply.

    http://www.digikey.com/product-sear...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
     
    Last edited: Aug 6, 2013
  5. jibmums

    jibmums

    4
    0
    Aug 6, 2013
    Okay, I'm a little lost (not surprising since electrical stuff completely confuses me). *steve* above mentions using a 12V unit. You're saying a 6.3V unit, which is the voltage of the bulbs. Will any damage result if using a higher voltage unit?

    Amp-wise, am I correct that I need a unit that meets or exceeds the amperage of all the bulbs, so 2A or more for the LED bulbs? What would happen if I used a higher/lower amperage unit?

    I apologize for all the noob questions, I really ought to read up on this first before attempting anything that could potentially blow up in my face.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,223
    2,696
    Jan 21, 2010
    When you place 2 6.3 volt lamps in series they require 12.6V. 12V is close enough.

    But you don't want to change the wiring so the question is moot.
     
  7. jibmums

    jibmums

    4
    0
    Aug 6, 2013
    Gotcha. So series wiring requires double the voltage of parallel wiring. Was just wondering.
     
  8. KJ6EAD

    KJ6EAD

    1,114
    157
    Aug 13, 2011
    Excess voltage will damage things. Inadequate current capacity will cause dimming and damage or destroy the power supply or transformer. Extra current capacity will do no harm to circuit components and will increase the life of the power supply or transformer.
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,267
    Nov 28, 2011
    When you connect light bulbs in series, voltages add together and the current is the same for all.

    When you connect liight bulbs in parallel, currents add together and the voltage is the same for all.

    If your bulbs are already connected in parallel, you need to supply 6.3V to the bulbs, and the paralleled array of bulbs will draw a lot of current from your power source.

    KJ6EAD's post #4 on this thread has some good info and links.
     
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