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| 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 :D that clears everything up for me |
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