LED Power

[D_Harris]

I'm looking to get feedback on the most accepted way to wire up LED buttons and joysticks.

Is the conventional way to go with 5V or 12V? (Or is it relevant?).

And is it normal to run them directly to a switching power supply? (I'm wiring up an original arcade cabinet).

Thanks.

Darren Harris
Staten Island, New York.

[Necro]

Depends on the LED's.  If they are 5v LED's, use 5v.  If 12v, use 12v.  Normally, some have resistors in line to make them for a certain voltage.

Basically, just check the specs and wire them up hat way.  Wiring them to your power supply should be fine...I think.

[D_Harris]

Let me rephrase.

What factors go into deciding between 5V and 12v if you haven't already purchased the LEDs?

Thanks.

Darren Harris
Staten Island, New York.

[SavannahLion]

Depends on the LED's.  If they are 5v LED's, use 5v.  If 12v, use 12v.  Normally, some have resistors in line to make them for a certain voltage.

There really isn't 5V LED or 12V LED per se. LED's have a forward Voltage which is calculated along with a resistor value. The same LED can be used in either a 5V or 12V circuit simply by adjusting the resistor value. To use the formula from GGG it's

Resistor Value = (Available Voltage - LED Voltage)/LED Current

So a single 3.3Vf 20mA LED on 5V would require 100 ohm, same configuration on 12V would require something on the order of 470 ohms
Two LED's in serial on 5v wouldn't function correctly, even if you dropped the resistor. Would work fine if you wired them parallel. So on and so forth.

I'm sure someone else who actually went to school on this will chime in soon enough but this site will explain the basics: http://www.kpsec.freeuk.com/components/led.htm

@ D_Harris

Unless I purchased some LED's with a Vf that exceeds my source, the LED's rarely determines what voltage I want to run from. It's usually caused by the number of LED's I want to drive or what kind of restrictions I'm stuck with eg I'm sourcing power strictly from USB and have no other means of driving the LEDs. More commonly, it's just restricted by what parts I have available.

[D_Harris]

@ D_Harris

Unless I purchased some LED's with a Vf that exceeds my source, the LED's rarely determines what voltage I want to run from. It's usually caused by the number of LED's I want to drive or what kind of restrictions I'm stuck with eg I'm sourcing power strictly from USB and have no other means of driving the LEDs. More commonly, it's just restricted by what parts I have available.

No that is not what I'm asking about either.

Nevertheless, I've come to the conclusion that it obviously makes no difference whether one uses 5V or 12V LEDs, because there is no reason to use one over the other if you have 5V and 12V in your cabinet. (You might as well flip a coin).

Darren Harris
Staten Island, New York.

[BobA]

One reason to choose 12V over 5V is that there is usually more leeway to reduce the light output by reducing the voltage.  Eg: 12V leds will run fine on 9V, 7V and even 5V just at reduced light output.   5V leds cannot be lowered much or the LED threashold voltage cannot be reached.

[SavannahLion]

One reason to choose 12V over 5V is that there is usually more leeway to reduce the light output by reducing the voltage.  Eg: 12V leds will run fine on 9V, 7V and even 5V just at reduced light output.   5V leds cannot be lowered much or the LED threashold voltage cannot be reached.

That's if you're using an analog pot. It would still be a wash if you've got a bunch of LED's on there that your threshold is about as narrow as a 5v circuit.

It also wouldn't matter if you're using a control board since they control light intensity via PWM rather than analog output. Of course, if one is using such a board, then the question of whether to use 5v or 12v is already answered for you.

[D_Harris]

One reason to choose 12V over 5V is that there is usually more leeway to reduce the light output by reducing the voltage.  Eg: 12V leds will run fine on 9V, 7V and even 5V just at reduced light output.   5V leds cannot be lowered much or the LED threashold voltage cannot be reached.

Thanks.

I hadn't considered that light output may be adjustable. I'll be looking into that as a possibility. But as it is now I'm about to pick up an LED joystick and two LED buttons for Player 1 and player 2.

I'll have to inquire about what else would be needed to adjust output, and decide from there if it is worth the trouble.

Thanks a lot.

Darren Harris
Staten Island, New York.