Measuring

[Hero999]

Why do you nead a resistor?

Can't you just remove the LED full stop?

 

[ScuzZ]

I did removed the LED completely.

The LED was connected to the motherboard with a flat connector. I just simpy unplugged it.

 

[audioguru]

I did removed the LED completely.

The LED was connected to the motherboard with a flat connector. I just simpy unplugged it.

Then you didn't measure the current of the LED.

 

[Marks256]

Why is it that you need to know the current put out by the power indicator? If you want to power something that needs a large amount of current, just use a transistor...

 

[ScuzZ]

I have dual power supplies running my computer. I have the ATX which boots from the momentary switch on the front panel. I also have an AT power supply that runs the big current drawing components, which has to be turned on manually and turned off manually.

I was planning on using a transistor to 'amplify' the power from this Power LED to get enough volts to turn on a Solid State Relay, so that I'd only have to turn on my computer with one switch and shut off the same.

I'm planning on using this Power LED output to 'Base' the transistor as it's the first light to come on, and the last to go off.

 

[BrianG]

Forgive me for butting in here, but you could use the same approach, but tap into one of the 3.3v, 5v, or 12v rails? I would think it would be easier?

 

[ScuzZ]

I have no spare power rails, they are all being used and being used pretty close to the maximum output. Hence the dual power supplies.

 

[RODALCO]

You can put in series with the LED an opto isolator eg 4N35 or eq. so you can drive from it's output via an extra transistor a relay and then whatever you like and keep it galvanically separated from your computer power supply.

There are more ways to get to Rome

 

[ScuzZ]

That's exactly what I'm planning on doing. I've just been working out which route I had to take.

The components that are available are slim at best, so I need to be sure that I'm making the right choice. The more information on what's needed the better.

I was planning on using the LED output to run a transistor to power the relay. Just reading up on which ones are suitable.

 

[Marks256]

use the optoisolator.