How can I get my SB61G2 power LED 'lit' without a motherboard?

M

MERKMAN

Limp Gawd
Joined
Jun 7, 2004
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226
Two SB61G2 cases. One a complete system, one with just a power supply and 2 hard drives. Have linked the two power supplies, so when I turn on the PC... the other cases turns on as well. But the 2nd case has no connection to the front panel, so no LED's light up and let me know it's working.

Any thoughts on how I could make that LED "light" without a motherboard? Splitting the connection from the first case and passing it to the 2nd is probably the most obvious option, but that wire is VERY thin and I'm not sure how practical that is.

Would prefer something I connect to a molex connector and the LED that would "just work", but I have no idea if something like that is made. Any help is appreciated.
 
Think I saw this somewhere else, but wasn't clear on it.

I presume I just buy a 330 ohm resistor, solder it to the negative wire on the LED, and then solder a ground wire to other end of the resistor? Does the resistor need to face a certain direction? I've never done work like this before. :confused:
 
You are exactly correct. If you want to practice first, you can get a multi-pak of 330 ohm resistors from Radio Shack for a dollar, and you can also get a few 5V LEDs.


When you're working with LEDs, the most important thing is paying attention to it's maximum current, in most cases a low power LED will take up to 20 mA.

Using Ohm's Law, you have V = I * R, which when solved for R for a 20 mA, 5V LED gives a resistor value of 250 ohm. Since R = V / I is an inverse relationship, any resistor larger than 250 ohms will give you plenty of current limiting capability.

The only other thing to worry about is power (wattage). The equation for power is P = I * V or P = I^2 * R. Either will work. In the example I've given, power is 0.020 * 5 = 0.020^2 * 250 = 0.1 W. In this case, you would be just fine with a 1/4 W resistor.

Resistors are non-directional devices. They don't care which way the electrons flow through.


I graduated with a BS in Computer Engineering, so I'm happy to answer electrical questions as I have time to and even explain the theory behind the answers. However, if you get me into the more complicated questions like semi-conductor physics, I'll have to go brush up in my books.
 
Oh, before I forget, something else.

LEDs do care what direction the electrons flow. If you look at a LED you buy from Radio Shack you will see that one side of the plastic case is flat. The lead coming out of that side is the - side (the shorter lead), and the other lead is the + side (the longer lead).
 
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