Standalone LED system?

[NoBonus]

I want to add some LEDs to my control panel, but I do not want to tap into the power from my MAME pc.  I realize that standalone systems exist, but none are cheap enough for me (that I have seen).

[cholin]

Ahh easy!  You CAN use an old power supply with LEDs and resistors.  Make sure you calculate the values right and whether you're doing it in series or parallel.  Also, as for the on/off switch, you wire a switch to the +5 or +12 or whatever side of your circuit.  So where you get the molex, on the red wire, you would place the switch somewhere along that line before any of your LEDs.

Edit:  Why wouldnt you just use the power on your mame system?  It's basically the same, except it saves you a PSU.

[NoBonus]

Edit:

[cholin]

Im not sure what you mean.  Are you saying you're building just the control panel to interface to a computer, or are you building one of those panels with a computer inside of it, so that you can just hook it up to a TV?  Good luck with it either way 

[NoBonus]

I am building a free-standing control panel that can be hooked up to any computer with MAME on it.

[johnnysmitch]

^ a computer power supply might be kind of an overkill for just lighting up some LEDs for your panel... depending on how much lighting you have in mind, you might want to look into just battery powering it (LEDs have very low draw, even the ultrabrights), or getting a small AC adaptor or something along those lines (check out mouser.com, allelectronics.com), which would save you a bunch of space, and possibly even some wires. If you're really feeling adventurous, you could rig it up to power the lighting off the USB port, too.

[Trimoor]

Don't bother with a spare PC power supply for just a few LEDs.  Use a 5-12V DC adapter, commonly called a wall wart.  They are cheap and extremely simple to use.

Or you could use batteries.  Buy a 12V rechargeable lead acid battery, and it will drive LEDs continuously for months before needing a recharge.

[NoBonus]

How do I rig up a switch and leds to a battery?  Do I find a LED flashlight and rip it apart? If so, where do I get one for cheap?

[oldsage]

I've been thinking about adding an extra PSU for my "interface box"... You guys make it sound horribly unneeded, but I'll keep mine because of extendability - might want to add a "shocker module" to my cab one day...

Back to the topic - do i need an individual resistor for each led if i power them off a PSU? I'm not that familiar with this stuff... What do you need a resistor for anyway?

(sorry if I'm hogging your thread... If this is unrelated feel free to ignore me...)

[tetsujin]

Back to the topic - do i need an individual resistor for each led if i power them off a PSU? I'm not that familiar with this stuff... What do you need a resistor for anyway?

You need the resistor to prevent too much power from going to the LED.  Too much power will cause it to burn out.  You need to have one resistor per LED if they're in parallel - if they're in series, you can use just one.

[cholin]

AS LONG AS THEY'RE THE SAME COLOR!  Electricity takes the easiest path.

Absolutely beautiful tutorial: http://lsdiodes.com/tutorial/

It's short and it explains everything.

How do I rig up a switch and leds to a battery?

Get a battery pack with wires first of all.  Then, wire them up the same way as you would with a PSU, red is positive, black is negative(ground).

[NoBonus]

So, I guess the real question is how many 5mm Blue 5900mcd LEDs do I need to properly illuminate a transparent blue trackball?  Is there a better Blue LED choice? is 5mm overkill? Should I look for the THC3 11000mcd LEDs?

[cholin]

I think that 2 regular blue ones should do the trick, especially if you buy a cheap dollar-store flashlight and use the shiny plastic reflector.

[Gamecab]

I want to add some LEDs to my control panel, but I do not want to tap into the power from my MAME pc.

[Trimoor]

Or you could use the 5V connection on your keyboard encoder...

[cholin]

That's what I dont understand, why you wouldn't just take the 5v from the MAME machine through the keyboard socket.

[NoBonus]

I'm using a Keywhiz eco, where is the 5v?

[Tiger-Heli]

I'm using a Keywhiz eco, where is the 5v?

Lower left pin, labelled V - (when viewed with the logo up and the keyboard connector to the left)