PUSH BUTTON LED POWER!!

[premier]

Hi Guys,

Have a few questions regarding the illumination of some push button leds.
Hoping somebody can shed some light on the matter.


Looking to illuminate 17 push button leds in my MAME cabinet.
I want these to be permanently lit and I want to use a pc power supply to do the job. I will be slicing a Molex 8981 using wires red (+5v) and black (-).
The buttons at hand are Ultimarcs "Ultralux" translucent push buttons - see link - which have a 5V led built in.



I have read some contradicting info regarding the illumination of multiple LEDS from one power source - and am a little confused.

Basically I would like to know the following:

1.
Are resistors required? - Ultimarc quotes the following on their website: If you simply want to light the buttons permanently, just connect to a 5 volt supply, such as from a PC hard drive power connector. Using our pre-made "daisy-chain" harness will save a lot of time.
Is this the case? I cant seem to see anything that resembles a resistor built into the led holder. Written on the LED is: JA 5V DC

2. How should i wire all 17 up? Series or parallel?


According to http://led.linear1.org/led.wiz -

entering the following information
Source voltage: 5V
diode forward voltage: 5V (a guess? this is what is written on each led)
diode forward current (mA): 20 (a guess?)
number of LEDs in your array: 17

returns this result:
parallel connected with 100 ohm resistors on each led.


but entering this info

Source voltage: 5V
diode forward voltage: 3.3V (a guess? - but as recommended by the site)
diode forward current (mA): 20 (a guess?)
number of LEDs in your array: 17

returns this result:
parallel connected with 1 ohm resistors on each led.


SO...

do I use no resistors? 1 ohm resistors? or 100 ohm resistors? or other?

can anybody shed light onto this!?

 

thanks in advance!

[matsadona]

1 : The Ultralux button LED lamps have a built in resistor so you don’t have to bother about that (or use that formulas). Just hook them up to any 5VDC source.

2: You connect all 17 LED lamps in parallel (in this case)

Regarding LED’s in general you always need a resistor in series to limit the current. And you should not have LED’s in parallel with just one resistor… you need one resistor for each parallel string of LED’s.

[premier]

thank you kind sir 

that clears everything up for me