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Powering multiple coin door LEDs off a 5v USB tap cable
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krick:
Say that I had a 4-slot coin door with 4 incandescent light bulbs.

If I wanted to replace all the bulbs with 5v LEDs, and then power them off a USB port using one of these cables...

http://groovygamegear.com/webstore/index.php?main_page=product_info&products_id=299

...how do I need to wire them (parallel, I assume) and what sort of resistor(s) are needed?

Also, does anyone sell pre-made 5v LED wedge lamp replacements, or do I need to roll my own?
2600:
For the LEDs, but the cluster ones from Happ (cluster has 3 leds instead of a single).  I believe Divemaster sells them.  They have a built in resistor.  Not a lot of the wedge ones have built in resistors and they will die rather quickly without it.

I think tapping into the USB is a mistake, but people do it.  Wire them in parallel and the USB bus "should" have enough current to power all 4.
krick:
Personally, I'd just tap off the 12v line in my power supply, but I know of someone who has a MAME cab based off a laptop.  So powering off the USB is the only way to go unless they want to get a separate "wall wart" just for the coin door lights.   I'm not sure what they're doing about a marquee either, come to think of it.

Frankly, I'd never try to power a cab off a laptop.


EDIT:
I think these are the HAPP lights you're referring to...
http://www.happcontrols.com/lighting/915wb61w.htm
DeLuSioNal29:
Tapping off the 12v power on your power supply is fine for normal coin door bulbs, but for LEDs you would want to use 5v.  12v would pop the leds.
Zebidee:
USB ports are theoretically rated to supply 5v at 500mA, which is enough current to run up to 25 normal LEDs at 20mA each.  So USB power should be sufficient for a handful of LEDs.  For example, JPACs run on 5v USB and look how many LEDs they support (5 or more), in addition to their video amp and keyboard interface functions.

Using 12v for LEDs is fine, but the wiring is a little trickier.  Instead of wiring them all as single LEDs in parallel, you should wire them into series-wired arrays of three or four or five LEDs, with each LED-array wired in parallel.  each array will need just one limiting resistor. 

Look below for a great LED matrix calculator.  this tool will tell you how to design your LED matrix and what limiting resistor to use depending upon your type of LEDs, current source and other specs.  It will even draw a circuit diagram for you:

http://led.linear1.org/led.wiz

For example, I could make an LED matrix using four red LEDs rated at 2.5v/20mA, wired in series behind a single 27ohm 1/2W resistor and run off the 12v rail.  Total power draw would be under 100mA, well within safe range.  You could then run four of these arrays in parallel from the same 12v rail, for a total of 16 LEDs with a 'safe' power draw of 400mA.
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