Installing LEDs

[SinCrisis]

Hey all,

I want to install LED lights for the HD activity and power lights for a case and I was wondering how I would go about wiring it? This is probably a dumb question, but I honestly have no wiring experience. The LED lights im looking at all have molex connectors but not the two wires i see on the original activity LED lights.

[slaveofconvention]

You have a couple of issues to overcome, depending on how many leds and hard disks you're going to be using. If you simply want a couple of leds in place of the original then its pretty simple. If you want whole arrays of leds then you're going to need a couple of extra parts. Wiring too many leds direct to the motherboard header can damage the board due to excessive power draw. A simple circuit using a fast relay will let you run an almost unlimited amount of lights. If you want different lights for different drives, things get more complicated and potentially much more expensive. A little more info please?

[mDust]

The LED lights im looking at all have molex connectors but not the two wires i see on the original activity LED lights.

Cut the molex connectors off and wire it up to one of these.

Or, if you still have the original, cannibalize it and wire the new LED to that. Make sure you plug it on the right pins. If the LED doesn't seem to be working, flip the plug around. LEDs are polar and will only work one way.

EDIT: Another thought: If the LEDs are originally molex powered, make sure they run fine at 2.6-3v...if not, find some that do.

[SinCrisis]

Well, i want two small LED Strips, kinda like these to blink and light up in place of the original LEDs, so the only harddrive activity blinking would be from the main hdd that you would normally use for the original case LEDS. I dont trust myself with any additional mobo tinkering, i think i am not experienced enough and would damage the board. Could i keep the molex on to provide the extra power and wire it so the motherboard sends the signals to turn on/off?

[mDust]

Could i keep the molex on to provide the extra power and wire it so the motherboard sends the signals to turn on/off?

Disclaimer: I'm not all that handy with electronic circuits.

I don't think you can just wire something like that. You'd need a switch of some sort. The switch would be powered from the 3v HDD Activity header and it would open and close the molex circuit as necessary.

[slaveofconvention]

You'll need a relay but it really isn't a complicated thing to set up. You need the kind of relay with 4 contacts (SPST - Single Pole, Single Throw) - 2 of them are the trigger, the other two are the open/closed contact. All you do is cut off the existing hdd led and wire it to the two contacts which trigger the relay, and then wire the other two contacts between the power source and the led strips. I'll get some more specific info and post an image to make this a little clearer....

[SXRguyinMA]

and make sure you get a 3v relay as well

[Konrad]

If I understand this right,
- an LED bar (~20mA per LED, wired in parallel), +12V molex power
- on/off signal coming from mobo, +5V HDD-activity LED header

... I don't think an electromechanical relay switch is the best choice. A switching transistor (rated at least 5V/1A) would be better. Higher efficiency, longer life, no clicky noises, cheaper.

Briefly explained here and here, many schematics found on google.

Regardless which switch you use, 2 tips:
1) wire a discrete resistor to each LED to equalize power distribution
2) attach a variable resistor in line to all the LEDs to allow brightness control (wiring from the pot dial can be drawn to the front of the case if you like)

[SinCrisis]

Oh wow, this is way more complicated than i expected, i dont know what half of these parts are or how they work...

I read the links, and i have a few questions:

Wont using the transistor then make me use more power than necessary?
Where do I find these parts?
What are there risks if I set this up incorrectly? ie will it fry my leads, board, or leds?

[Konrad]

Wont using the transistor then make me use more power than necessary? Where do I find these parts? What are there risks if I set this up incorrectly? ie will it fry my leads, board, or leds?

Aha, well ... explaining all about electronics and transistors might take too long. If you're comfortable using relays then go ahead, it should work fine, there's no requirement that you engineer a circuit beyond your present electronics knowledge.

Here's a working circuit which can drive 9-10 LEDs from the mobo. Absolutely no risk of damaging the mobo; it even uses an optocoupler to be electrically isolated. (I think the optocoupler was used to allow the designer the option of safely using +12V/inverter CCFL lighting instead of +5V LED bars.)

- JP2 is the mobo HDD LED header, only connect pin1 and pin2 (pin 3 unused in this application, the +5V comes from a PSU molex); if you plug them in backwards then the LED circuit just won't work until you plug it in correctly. The simplest way to build the circuit might be to connect all the GND lines together, either on the circuit backplane or directly to the LED-gizmo's "chassis".

- Parts are all fairly common. You can buy them locally (for about $3-5 maybe), order online, or salvage them.
BC549 is just an NPN transitor, a 2N3906 would work as well.
4N25 is the optoisolator; not strictly necessary but soothes paranoia. This will be the part that suffers the most electrical "strain", ie: it'll be the "fuse" which fails before anything else.
LM3914 is the LED driver (with integrated resistors); again, not strictly necessary if your LEDs are already integrated into a single block. (The LM3914 is designed to run "graph style" LED bars.)

Switching latency at these voltage levels are ~10ms, you won't notice it visually. Power consumption by these parts is ~25mA when active (plus 10-20mA per LED).