gauge of wire to use

[xtremediver]

I recently built a mp3 jukebox I have 14 lighted pushbuttons and 1 coin light. In my arcade cabs I just used a ac-adapter but that won't do for all of these lights. I am going to go into the yellow and black wires on my cpu power supply for the 12v which should be enough power for all the lights. I used 22 gauge for the pushbuttons is this big enough to do all of the lights with or should I go with 18 gauge?

[grafixmonkey]

I'm assuming you're using incandescent lamps.  I tested one of those and they draw around 150 - 160 mA from my PC power supply.

22 is definitely big enough for at least two or three lights at once.  If you run a single loop of 22 wire to each light from the power supply, you have nothing to worry about.  If you run a single loop of wire and try to put all your lights on it in parallel, you should break it up into different loops with 4 lights each, or use the thicker wire.  

If you're using LEDs, you can run everything off one loop no prob!

All that'll happen if it's too thin is the wire might heat up.  You can just feel it after running the lights for a few minutes and check.

[xtremediver]

All 15 lights stay lit as long at the cpu is on. I'm a bit reluctant to use the cpu power supply though because I did burn out a 12vdc and don't want the same to happen to my cpu power supply. The number on the bulbs are #161. And yes I do have all the lights daisy chained together. I can change this though.  I did look into the led lights but not willing to spend $250.00 for 15 of them. So would it be possible to still us a 12vdc and just use 18 or 16 gauge wire instead of the 22. Would it still burn it out? I could get two of them and split the lights in half too if that would help.

[grafixmonkey]

I can't answer for certain given only the information that's there.  To answer fully I need to know what is in the computer, what else is connected to its power supply (besides the computer and the lights), and how much current your bulbs draw.   But I can say a few things without all that:

The gauge of wire you use will not change the total power your lights consume, neither will how many are on each loop.  So, if you have enough lights to burn out a power supply, the wire you use or how you loop them won't change that.  However, I misread your first post and thought you had five or six lights...   you should definitely not use 22 gauge wire if it's going to carry 2.4 amps, which is what it would with all those lights in parallel.  You can use thicker wire, or you can put only three lights on each loop, and have five loops of wire.

If you are using incandescent lamps like mine from the illuminated pushbuttons I got from Happ (# C161) they consume 160 mA when plugged into a 12v power supply.  12volts * 0.16amps is 1.92 watts each, and with 15 of them that's about 30 watts.

I have an old 300 watt AT power supply I use for testing circuits.  On one side of it is a sticker that tells how much power each connector can supply.  For mine it's 168 watts for the 12v connector.  That's about half of the power my unit can supply.  Lacking any real specs to look at right now, I'd venture to assume that holds for other power supplies as well (makes sense - two sources, 5v and 12v, half the power each...).

So, take the minimum wattage power supply your particular pc should be able to work in, compare to the power supply you have, and half of the difference is the room you have for powering other stuff off of the 12v connector.


I should also mention that you can power your lights off of any power supply you stick in there, so you can easily buy a 30-40 watt 12v power supply from RadioShack (shudder) or maybe some other parts supply store like www.newark.com or www.digikey.com, and those often come in a package that's easy to just bolt or screw to a wood surface, plug in, and connect to your lights.  Then you have to find a way to turn the lights on and off with the computer, but there are numerous methods for that.

Or you can buy a 450 or 500 watt power supply for your PC, and have plenty of extra power.

[grafixmonkey]

I should also mention, when the computer is first powered up, there is a strong burst of current being drawn from the power supply, because it is spinning up every drive in the system and recharging all the capacitors that have emptied themselves.  This is the most demanding time for the power supply, and the time when having extra power-consumers is most likely to burn it out if you're cutting things close.

So, you might consider putting your lights on a switch so you can turn them on after the PC starts up.  You could use a momentary contact switch and a single-pole double-throw relay to make a push-on stay-on switch that would automatically turn off when it lost power, so you wouldn't forget to turn it off.

Here's how to do it:

[xtremediver]

ok, first of all thanks for your help. This is what I've done. I re-wired the lamps using 14 gauge wire. I had a 12v ac-adapter but I decided to get a different one. I have one that is hooked up to it now that can either be set to 18 or 24. Both shine up just the way I want it to look. Question? which setting should I use to ensure it doesn't burn out in a couple of hours like the 12v did? Also keep in mind the 12v was hooked up with 22 gauge wire and not 14. And all 15 lamps are dasiy chained together.

Thanks

[grafixmonkey]

You're fine daisy-chaining all your lights with 14 gauge wire for sure.  

You still didn't say what wattage your power supply is or really what kind of bulbs you have, although I assumed they're 12v bulbs from your other post.

Did you mean to say it switches between 18 and 24?  so you're powering 12 volt lights on 18 volts?  (not a good idea - just checking?)

If you have to choose between either 18 or 24 volts on 12v bulbs, use 24v and put loops of two bulbs in series, in parallel...   like this:

[xtremediver]

sorry, the light bulb is 16v and am using the adapter not the cpu power supply. the adapter is set to 18. I thought since I was lighting 15 lamps that alittle more power wouldn't hurt. I figure it would just burn the bulb out alittle prematurely. I can always take that 18 back out and put the 12 in that I have. If you think that would be better and safer.

thanks again.

[grafixmonkey]

I'm reading a little misconception about voltage here...  the voltage is not something the thing can supply, it's something that it WILL supply.  Whether the device takes it or not.  Picture having 30 people all running off a 5 foot ledge, and jumping down to the ground below.  I'd say those people are rated for about 7 feet - jump them off 7 feet and they're fine.  You raise that to 9 feet though, and you're running them above their rated "voltage."  Chances are they'll survive but will be gradually getting minor injuries.  Put them on a 12 foot ledge and chances are your little "people device" will be broken pretty quick.  But they'll still be jumping off a 12 foot ledge.  They won't be jumping, but landing 5 feet off the ground, with "power left over."   The wattage of your power supply is what's important.  It's how many people it can shove off the ledge in a second.  Problem is, the people are shoving themselves off the ledge.  They determine how many jump per second.  The power supply has to keep up, or it will burn out.

Running a 16v lamp on 18v isn't much of a problem.  Those power supplies often only get within half a volt of their target anyway.  The lamp will burn a little bit brighter, maybe a little bit hotter, will burn out sooner, and will draw more power.  Per lamp.  Since your lamps are 16v and mine are 12v, I can't make a guess how much power they draw so if you wanna know if things will burn out before you plug it in, you'll have to measure yourself.

If anyone you know has a voltmeter or multimeter, try to measure the current (not voltage!) going through one.  Say you get something like 180 mA.  That's  0.18 amps.  

So, take your measurement...  (let's pretend it's 0.18)  and do this calculation:

current * voltage * number of lamps  =  0.18 * 18 * 15

In this case you get 48.6.  So your power supply better be able to supply at least 50 watts, or guess what it's gonna burn out too.  Unfortunately those power supplies RadioShack sells are usually 20 or 30 watts so you'd better check on this if you don't want anything to start smoking.  And it might not start smoking right away.  It might start smoking some day when you've left it on all night, or off at work, and aren't watching it.  If your unit can supply 60 watts, it's just about sure to be ok.


At this point I'm gonna suggest you try and find an old AT style (not ATX) power supply from a computer shop around town.  Chances are someone will have one somewhere, and it should be very cheap.  Those things are almost never rated for less than 200 watts, often 300 or above.  You can use the power connectors to power your lights if you use 12v lights.  There's a 16 volt connector in there too if you know where to look but it might not be able to supply 50 watts.

[xtremediver]

ok, I'll probably buy a second power supply. Just out of curiosity though. My current power supply is  200w. All it is powering is the motherboard, C:\ and D:\ drives. I have one extra A:\ drive power plug and 3 regular power plugs. Although one of those is split off of another. So it would really be only 2 power plugs. The computer itself is P3 933. I haven't yet bought a multimeter to test the current. But was wonderng if I split the lights in half. 8 on one power supply and 7 on the other. Would my cpu power supply be ok? Or would I just be better off getting the 2nd power supply?