Archived from groups: alt.comp.hardware.homebuilt (
More info?)
On Thu, 08 Apr 2004 18:22:20 +1000, Franc Zabkar
<fzabkar@optussnet.com.au> put finger to keyboard and composed:
>On Thu, 01 Apr 2004 17:42:57 -0500, Gary Tait
><classicsat@yahoo.cominvalid> put finger to keyboard and composed:
>
>>On Wed, 31 Mar 2004 17:21:56 -0600, Persnickety Tim
>><tarmstrong@kmts.canthespam> wrote:
>>
>>>Anyone know of a simple way to have a separate HDD active LED for each
>>>disk? Also interested in moving or copying my case power LED and
>>>CD-ROM LED, because my case is mounted sideways, and the front panel
>>>is not very visible. Figure I'll just splice those in, but a single
>>>LED to tell me that at least one hard drive is active seems like poor
>>>information. I'd like to see which hard drives are active, and how
>>>much. Pointers?
>>>
>>>Tim
>>
>>Pin 40 on each drive goes low with disk activity. You could break that
>>wire away from the cable, and conect that to individual LEDs, which
>>will be connected to +5V with a 220 ohm 1/4 W resistor.
>>(Except for CDRW drives, which often have dual colour LEDs, if that is
>>important to you).
>>
>>There is generally nothing wrong with relocating the front panel
>>electronics.
>
>Pin 40 is ground. Pin 39 is /ACT. See this document:
>
http://www.ent.ohiou.edu/~welker/ide.txt
>
>The author writes:
>"A low level on [the /ACT] pin indicates that the IDE device is busy."
>
>I'm not sure how the mainboard's IDE controller would react if the
>/ACT pin were cut. I suggest that a better method would be a circuit
>such as the following:
> +5V
> ___
> 1K LED1 |
> master pin 39 o-+-/\/\---|<|---o +5V |
> | 4K7
> |-----|<|------| |
> D1 & D2 |--------+--0 pin 39
> |-----|<|------| controller
> |
> slave pin 39 o-+-/\/\---|<|---o +5V
> 1K LED2
>
>Diodes D1 and D2 would be germanium signal diodes with low Vf. Pullup
>resistor 4K7 may not be required.
Further investigation suggests that this circuit may have problems
detecting the slave HD during the POST. According to Seagate, pin 39
(DASP, Drive Active or Slave Present) is a dual purpose pin.
From Seagate's "ATA Interface Reference Manual":
(1) When drive is slave, this pin is used during power up to signal to
the master that a slave is present.
(2)At all other times, the signal is active when the drive is
executing a command, and can be used by the host I/O adapter to send
an activity signal to an LED.
- Franc Zabkar
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