Resister LED...

idleup

On this schematic, the power supply shows a resister LED, I was just wondering why it doesnt designate the resistance or voltage for the LED. Dont they come in different resistances or am I confused?

http://www.parallax.com/dl/docs/prod/schem/2440BrdSchem.pdf

- Matt

Robert Kubichek

idleup said...
On this schematic, the power supply shows a resister LED, I was just wondering why it doesnt designate the resistance or voltage for the LED. Dont they come in different resistances or am I confused?


http://www.parallax.com/dl/docs/prod/schem/2440BrdSchem.pdf



- Matt

It is a led with an internal resistor, usually meant for 5v logic circuits...

Bob N9LVU

idleup

Is there a reason the resistance isnt listed? does it only come in one resistance?

- Matt

Chris Savage

Matt,

·· Resistor LEDs come with resistors for certain voltages.· That is, you can buy an LED rated for 5V and you can also buy one rated for 12V.· There's no reason to know the value of the resistor, since it's designed usually for a specific voltage.· Knowing that the one in our circuit runs off 5V, you simply buy a 5V LED.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Robert Kubichek

idleup said...
Is there a reason the resistance isnt listed? does it only come in one resistance?


- Matt

It's not the resistance, it's the supply voltage that the led is going to be used with that is important..

I think that in the schematic "Resistor Led" means a led with an internal load resistor...

Also some leds can be used with a wide range of dc voltage " 5 - 12", as they have an internal
dc regulator plus a resistor....

I have both types, and some of the variable voltage leds are also flashers...

Bob N9LVU