suggest LED + transistor for PC?

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?)

Reply to
Impmon
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+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

Reply to
ehsjr

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