suggest LED + transistor for PC?

[Impmon]

I wanted to change the indicator LED a bit. First off, the HD
indicator LED is uselessly dim because of a cheap optic guide so I'm
going to discontinue that LED and I wanted to use the light bars
instead. The light bar is lit by 4 LEDs total. I checked, the hard
drive header's + side is tied to +V source, and the - side floats high
for no activity and goes low for activity.

How do I make it so the light bar is ON when there's no activity and
goes off when there's activity? Obviously transistor is needed since I
doubt the PC motherboard is designed to handle 4 LEDs at once.

I am getting blue/yellow bi-color LED to replace the stock LED for
another reason: the standby mode is also tied to +V source and - pin
goes low when PC is in standby mode. So it'll be blue steady, flashing
blue with HD activity, and yellow when standby. The yellow side will
also need driver transistor to control 4 LEDs but should be much
simplier as it's on when mobo's header goes low. PNP should do the
trick, collector on the LED cathode side, resistor from base to mobo
standby LED header, and emitter to ground (unless I'm wrong?)

 

[ehsjr]

Impmon wrote:

I wanted to change the indicator LED a bit. First off, the HD
indicator LED is uselessly dim because of a cheap optic guide so I'm
going to discontinue that LED and I wanted to use the light bars
instead. The light bar is lit by 4 LEDs total. I checked, the hard
drive header's + side is tied to +V source, and the - side floats high
for no activity and goes low for activity.

How do I make it so the light bar is ON when there's no activity and
goes off when there's activity? Obviously transistor is needed since I
doubt the PC motherboard is designed to handle 4 LEDs at once.

+12--- -------------+
e\ /c |
--- |
| [LightBar]
[1K] |
| [R]
IN --+ |
|
Gnd ------------------+

IN goes to wherever you have the low for activity and
high for no activity. The PNP can be whatever you have
on hand - compute R to keep current through the Light bar
LEDs to 20 mA or less.

Ed

I am getting blue/yellow bi-color LED to replace the stock LED for
another reason: the standby mode is also tied to +V source and - pin
goes low when PC is in standby mode. So it'll be blue steady, flashing
blue with HD activity, and yellow when standby. The yellow side will
also need driver transistor to control 4 LEDs but should be much
simplier as it's on when mobo's header goes low. PNP should do the
trick, collector on the LED cathode side, resistor from base to mobo
standby LED header, and emitter to ground (unless I'm wrong?)