Basic power source question for parallel light bulbs

Discussion in 'The Projects Forum' started by mjolnir76, Aug 5, 2014.

  1. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    I'm connecting 6 light bulbs with individual switches to a single power supply.

    The light bulbs are all 6.3V .25A (which should be a 25ohm resistance, yes?)

    What would be the best power source? In other words, what kind of batteries and how many should I put in this? Also, should I run them in series or parallel or a combo?

    Lastly, do I need any resistors in my circuit to prevent a blowout if all the switches are turned on at once?

    Thanks!

    [​IMG]

    Here is a link to the circuit if the image doesn't come through.
    https://www.dropbox.com/s/ynynsyv3vpjiteh/circuit.jpg
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    If you put light bulbs in series, you only need one switch.
     
  3. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    Right, I'm actually making a activity board for my daughters. I want each switch to activate a single light (i.e. when they push the green button, the green light lights up). However, I only want to do a single power supply to save on space.

    I just don't know how big of a supply I need and whether there will be a problem if the girls turn on ALL the switches at once.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    If you want individual switching, series is not an option. Six bulbs in parallel drawing 0.25A each is a 1.5A load. So your battery needs to be rated to deliver at least that amount. Four AAs in series would work but not for long if all 6 lights are on. If it's very intermittent, say an average of ~1 light on at all time, it will last longer.

    If you need more juice, there are many options that depend on how much room you have, cost, weight restrictions and so on. Do you need to be able to recharge the batteries?

    You should consider adding a 2A slo-blo fuse, in case the kids figure out how to short the battery.
     
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Are we talking actual light bults or LED?
     
  6. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    These are actual light bulbs, not LEDs.

    In terms of space...I have a about a 6"x8" space at a depth of 2" to work with.

    Ideally...the solution would be cheap and light. In terms of recharge, that isn't necessarily so long as I could get a few weeks of use out of these. I would assume that most of the lights would be intermittently used most of the time.
     
  7. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    If they only have access to the switches and the power supply is mounted INSIDE the box that the switches are on, is there any way to short the battery with JUST turning on/off the switches?

    Also, where would I add the fuse, between the power supply and the first switch?
     
    BillB3857 likes this.
  8. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    So far I am thinking something like this:

    [​IMG]




    This is simulation, not real thing.

    I am using lamps. Notice the lamps are rated 6.3 volts, 1.575 watts. The 6.3 volts came straight from you. This simulation does not have current rating for lamps. So. You said that the lamps are rated for 0.25 amperes. Power=Current*Voltage, 0.25*6.3=1.575 watts, that is where 1.575 watts came from.

    wayneh suggested four 1.5 volt batteries in series, that is what I did, you can see on the left four batteries connected in series and each battery is 1.5 volts. The total voltage here is 1.5*4=6 volts.

    Each lamp has a switch. This switch will activate only one lamp, the lamp above it. So lamp X1 is activated by switch J1, lamp X2 is activated by switch J2, and so on. In the real circuit the switch can be placed either above or below the lamp. I put it below the lamp in the simulation, but that is personal quirk and not a requirement.
     
  9. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Go and get a 6V car battery, you are going to need it...

    Better yet, get a 6V 2A Wall-Wart.
     
  10. yourownfree

    Active Member

    Jul 16, 2008
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    I wish I new what you plan to do with it. Seems to me leds would be better if its just a toy. If you insist on using this circuit remember you cant physically check the bulbs with your meter and get an accurate reading on the resistance. The reason is it has a positive coefficient, meaning the resistance goes up when the bulb turns on. not many people know this so thought I would mention this. Now the batteries. To me it depends on how long you want the lights to be on. As you know they have flashlights that use the 5 watt led bulb and they last for a while with the batteries they use. If you want this to be portable then why not make the batteries removable and use hi current re-chargeables. Now you could use a 12 volt battery from say an old computer uninterrupted power supply. Add another bulb in series. Just one is all you need from battery to the set of bulbs.
    If you plan on the circuit as is Just use "D" batteries for your circuit an you will be fine.
     
    Last edited: Aug 5, 2014
  11. Metalmann

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    Dec 8, 2012
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  12. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    It's going to be an activity board for my 10-month-old daughters. It has a variety of latches, knobs, etc. to teach fine motor skills. It also has a variety of switches (toggle, pull chain, push button, light switch, etc.) and the plan is to connect the switches to lights mounted on the top to teach cause and effect.

    They are all mounted on two pieces of 3/4" plywood mounted back to back with 2x2's. I'd like to be able to store the batteries in the space between the plywood...which eliminates the 6V, I think. I'd also like it to be stand-alone...though the 6.5V wall-wart is a great idea.

    The lights will be turned on/off repeatedly, but wouldn't be on for long durations...maybe a few minutes at a time.

    Hope this info helps. I appreciate everyone's ideas/info!
     
  13. wayneh

    Expert

    Sep 9, 2010
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    No, you don't need a fuse in this situation (although it's never a bad thing). I thought the wiring was exposed and might be casually shorted. Any battery pack capable of lighting all six bulbs would also be capable of an impressive short.

    A battery pack of 4 quality AAs will give you ~10 bulb-hours of light. That's 1 bulb for 10 hours or all 6 bulbs for only ~1.5 hours. If you need more time, you'll have to choose a different battery type.
     
  14. wayneh

    Expert

    Sep 9, 2010
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    Hmmm.. To my mind that means the bulbs should not be exposed. They can get warm, they're not hard to break, and they easily screw out and would then present a choking hazard.

    Another problem is when a light is left on to run the battery down. I guess an adult can intervene.

    Love the busy box idea, though. Very good for kids .
     
  15. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Pretty hefty construction. Could you use 1/4" plywood on a 1x3" frame? That would give you an inch more depth and you could probably use D cells. Also, it would be lighter for your 10 month old, but still be strong enough for use.
     
  16. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Another idea! Put a timer in the power circuit so that it only runs without being reset for a defined amount of time. Reset could be recycling a master power switch (which you plan on including, right?)
     
  17. williamj

    Active Member

    Sep 3, 2009
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    shteii01 stated...

    "Each lamp has a switch."

    "I put it below the lamp in the simulation, but that is personal quirk and not a requirement."

    Just one point of safety in working on, problem solving and/or maintaining a circuit (and I know it's not 'required' here). I've found it common practice to place the switch between component (the light) and the "HOT" lead (for AC) or the "POSITIVE" lead (for DC).

    Indeed all power should be off, but by turning the switch off too, it adds an additional measure of safety (for any circuit) incase the power is inadvertently turned back on.
     
  18. wayneh

    Expert

    Sep 9, 2010
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    The user is 10 months old. There is no arrangement of switch and bulb, other than proximity, that will matter because the device will be rotated in 3 dimensions. There is no up or down.
     
  19. mjolnir76

    Thread Starter New Member

    Aug 5, 2014
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    djsfantasi: It's hefty on purpose so that the girls aren't able to move it around (i.e. knock it over). But a switch to 1x3 as the frame isn't out of the question to gain some added room on the interior. The timer is a nice idea, but think that might defeat the purpose (i.e. teach cause and effect). I like the master switch idea.

    wayneh: Ideally the girls will use it with an adult present so that all 6 lights aren't on all the time, so even 6 hours of bulb time would be enough. The bulbs will be covered so that the girls can see but not touch them.

    I think I'm going to run with the 4AA batteries in series and then run the lights all in parallel and see how it goes. I will also make the batteries easily accessible (for me, not the girls) so that I can replace as needed.

    ADDED ELEMENT...

    I just found a 12V 0.18A fan (presumably for a computer?) in a box of electronics odds & ends. Would love to use this but am now working with 2 voltages (6.3 for the lights and 12 for the fan). Can I use an A23 battery (12V) to run just the fan?

    The project is still a work in progress, so I'm open to other ideas still. Will try to get a picture of what I have so far in the next day or so!

    Thanks!!!
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I'd still consider LEDs, drill tight hole in board & cement in place. Lots of colors available, much lower power requirement.
     
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