Illuminated Switches resistors? CF...

[Marco]

Hey all,

as the topic indicates I want to wire illuminated switches on the accent LED pads of a CF. (To use them as switches and accent leds at the same time... ;>)

The manuals says the CF outputs 3.3 v and 18 mA.

The LED has a Vf of 2.8v and a foward current of 20 mA...

Do you think it can handle the 3.3v without a resistor or do I have to wire one in? The current is a bit higher as the CF provides...

Any answer will be greatly appreciated!

Thanks in advance,

Marco

[Ari-Jaq Xulden]

Rule of thumb "Always use a resistor!". remember though its not the voltage that kills an LED rather too much current. In this instance I have used what is referred to a jumper, Its a 000(or 0) resistor. without a problem.

[Skottsaber]

You should use a 27 ohm resistor.

[Marco]

kay I thought the led might hanlde the 0.5 v that are too much because it gets less mA than needed...

[Marco]

How much watt?

[Sunrider]

In the manual it says not to draw more than 18ma and that the current is not regulated for you. That is why the resistor pads are there. Just get the right size and value resistor and solder it to the board.

[Marco]

its also possible to solder it to the switch right and not directly to the board? I dont want to solder it right on to the board...?

[Skottsaber]

It is, but remember that your switch will probably be moved around more in your install than your board, so the chances of the connection breaking are slimmer if it's on the board.
But no, there isn't a difference in operation.

[Marco]

one lil q... there is no such thing as too much watt right? if the calculator says 33 ohm 0.125 w I can use a 33 ohm 0.5 w resistor without any problems right? the led wouldnt be less bright or anything like that?

[Skottsaber]

Nope, your resistor just gives out a little less heat for the greater surface area.