Drive independent activity LED's

A Mod from:


-Using rounded cables-

This guide will show how to make a separate LED to show exactly which drive in your system is active.

This modification is done without warranty, I did this to three 80 conductor cables without any problems, if you screw up don't blame me.

First off this Mod only seems to work on IDE Harddrives, the two CD-Roms I connected (one Pionner DVD, and one Lite-On CD-RW) don't even use this pin on the IDE cable.  The CD-RW LED is always on, and the DVD LED is always off.  If you wish to use this for those devices you will have to hack the LED in the front of the drive its self.

Now for a little information:

An IDE connector has 40 pins, they are as follows:

Primary, Secondary IDE Connector
Signal Name Pin Pin Signal Name
Reset IDE 1 2 Ground
Host Data 7 3 4 Host Data 8
Host Data 6 5 6 Host Data 9
Host Data 5 7 8 Host Data 10
Host Data 4 9 10 Host Data 11
Host Data 3 11 12 Host Data 12
Host Data 2 13 14 Host Data 13
Host Data 1 15 16 Host Data 14
Host Data 0 17 18 Host Data 15
Ground 19 20 Key
DRQ3 21 22 Ground
I/O Write- 23 24 Ground
I/O Read- 25 26 Ground
DACK3- 29 30 Ground
IRQ14 31 32 IOCS16-
Addr 1 33 34 Ground
Addr 0 35 36 Addr 2
Chip Select 0- 37 38 Chip Select 1-
Activity 39 40 Ground

We want Pin 39

Pin 39 is wired to a Motherboard like this (I made this using Eagle PCB):


The LED jumpers' negative pin is simply ran through two diodes (to keep the two channels apart), then directly to pin 39.

The 10K resistors are to make sure that when the Diode is off, the IDE activity pin's voltage is kept at VCC.

The positive side of the LED is ran through a 33ohm current limiting resistor to VCC (Usually about 1.6v)

Well, we will simply bypass all this and run the LED directly to pin 39 in the IDE cable it's self.

You can do this because Pin39 has nothing to do with the operation of you drive, just the LED.

The IDE Cable

I am doing this example with a 80 conductor cable.

If you use a 40 conductor cable Pin 39 is simply the second to last wire (NOT on red side)

Since and 80 Conductor cable has a ground wire paired with each signal wire.

So Pin 39 is the THIRD TO LAST WIRE on MOST IDE cables

(Check your cable first with an ohm or continuity meter first)

Cut carefully on both sides of the wire. 

Separate the third wire:

Then clip it in half (AHHHHH, don't worry your drive will still work, unless you cut the wrong wire)

Strip the wires, carefully.

(I added a quick disconnect and used heat shrink tubing to cover the connector)

The one on the Left is for the First IDE device, the one on the right is for the second IDE device.

Also note that when the second IDE device is ran the LED may still go off on your Motherboard (Dimming your custom LED, this does not happen in my system, but still I disconnected my IDE LED)

To fix this Either disconnect the one on the motherboard, or Clip Pin 39 between the Device connectors and the Motherboard connector.


The LED's


First you have to choose a resistor value that will keep the current on the LED's in spec.

I choose to run the LED's off the 5v line from my power supply, so I choose 150ohm resistors.

This should make the current for each LED 33 milliamps.

Mount your LED's however you want, I used some nice, but cheap LED's w/mounts from RadioShack

I didn't need ultrabrights as my case is behind a desk door most of the time.

Then wire each LED as the the schematic above, 

5 volts runs to the resistor, then the resistor connects to the positive side of the LED, the negative side is connected to Pin39 on each device you you have.

It should look something like this:


Connect the common 5V wire to 5 Volts

Connect the negative wire of each LED to Pin39 on each IDE device and you are set!

I love the way it works on my system.

The second animation is from Enak, a use on He used rounded cables Guide here -Click-