Dual colour power LEDs on PCs

Andy Burns · 2018-03-24T10:08:56+00:00

I've replaced the motherboard in a PC with a small SBC which has an intel 9-pin front panel connector[1] rather than just a bunch of header pins for LEDs and switches like a normal motherboard, the connector pins are labelled in the board's own manual[2] as 1 HD_LED_P 2 PWR_P/SLP_N 3 HD_LED_N 4 PWR_N/SLP_P 5 RST_SW_N 6 PWR_SW_P 7 RST_SW_P 8 PWR_SW_N 9 UNUSED so the power LED is between pins 2 and 4, and rather than a single on/off LED, it offers the ability to use a bi-colour LED. The way they're labelled PWR+/SLP- and PWR-/SLP+ I assumed it required a 2-pin LED with red/green wired in inverse parallel, such as I bought one, it lights up green when power is on, but not red when power is off (by reversing the connections I can make it light up red when on, but still not green when off, so it isn't a case of the LED being half dead). Presumably this means in reality it requires a 3-pin LED, such as And that I need to split the ground from e.g. the hard disk LED cathode pin to feed the power LED's common cathode, the labelling feels wrong though ... would you have read it the way I did initially? [1] [2]

Mar 24, 2018 21 Replies

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tabbypurr 8 years ago

if you added resistance on the green side that would help with the colour change

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Roger Hayter 8 years ago

I agree then that from your measurements the board simply doesn't do what it says it should.

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