Lighting Push Buttons

[Dillsta]

I have just ordered some push buttons with 12v LED's in them and i was wondering if you can wire them into the computers power supply instead of having to buy a LED-Wiz? If so could someone please tell me how.

Or if there is another method without having to spend to much money i would like to hear it as well.

Thanks Dylan

[Franco B]

Yep, you can run them off your PCs PSU, just wire the LEDs in parallel to the yellow (+12v) and black (ground) wires from a spare molex.

[This] video tutorial for LED coin door lighting may help you. Just wire in your LEDs instead of the bulb holders.

[web.geek]

Is there a limit to the number of LEDs you can have in series from a single 12v source?

[Dillsta]

Thanks Franco B, I was looking on the internet and people were connecting things sort of like this and thats where i got the idea. The buttons should be here in the next few days so ill tell you web.geek what happens with mutiple LED's connected.

Thanks, Dylan

[Franco B]

No problem Dillsta.

Is there a limit to the number of LEDs you can have in series from a single 12v source?

Yes, in series the combined voltage required to light the LEDs cannot exceed the source voltage. So for typical LEDs requiring ~3.5v you can only have three in series using a 12v source.

However, if you wire them in parallel you can run (almost) as many LEDs as you want as long as you don't exceed the available amperage from the PSU.

AFAIK each 12v lead from a typical supply guarantees 18A without triggering the current limit. So theoretically you could connect over 1500 (3.5v 25mA) LEDs in parallel to a 12v whilst drawing 12.5A

On a side note you could use the 5v from a USB cable but you are limited to 500mA.

[This] is a handy wizard for designing series/parallel LED arrays. It will also tell you what resistors you need and how much current you are drawing.

[Dillsta]

so im going to have to get some resistors before i evan try this out, right?

[Franco B]

If you bought buttons with '12v LEDs' in I imagine they are ~3.5v LEDs pre wired with a resistor suitable for 12v so they should be ready to go.

Which buttons/LEDs did you get?

[Dillsta]

I got some from www.ozstick.com.au

[Franco B]

Yeah you will be fine to run those straight off 12v with no additional resistors.

[Dillsta]

How do i connect the LED's parallel because i don't quite understand

Thanks Dylan

[Franco B]

Have a look [here]. It should help to explain things. 

[Dillsta]

  Ok thanks mate, thats what i sorta thought ya had to do be i wasn't too sure. Thanks For all ya help with this. 

[Franco B]

No problem, your more than welcome. Good luck!