Adding extra cables to 24 pin

[melovesleep]

Hello guys,

 

i have a question about modifying/adding extra cables to the 24 pin connector. What i want to do is to add a standby led in my build, so when the pc is off the led will be red and when its on it will be green. I already did some research but i am stuck now. For the green part i will just use the motherboard panel header, but for the red one i red that i need a 5 volt standby pin, that pin is not on my motherboard, Asrock B450 fatality, so i can use that. The only other way i thought of is to somehow use the stand by pin that's on the 24 pin connector. My question is, how would i go about adding extra cables to the 24 pin connector and is it even doable?

[AbydosOne]

15 minutes ago, melovesleep said:

but for the red one i red that i need a 5 volt standby pin

Quick note: the 5V_SB rail doesn't turn off when the PSU is active; it's always 5V all the time.

How much experience with electronics design to you have? My high level suggestion would be to splice wires into the 24-pin harness on the 5V_SB and the normal 5V  lines, and then run that to a circuit with a little bit of logic to the do the LED switching.

[melovesleep]

1 minute ago, AbydosOne said:

Quick note: the 5V_SB rail doesn't turn off when the PSU is active; it's always 5V all the time.

How much experience with electronics design to you have? My high level suggestion would be to splice wires into the 24-pin harness on the 5V_SB and the normal 5V  lines, and then run that to a circuit with a little bit of logic to the do the LED switching.

I have some experience but with bigger electronics, sockets etc, but not pc components. By a harness you mean some kind of extension? Thats the only thing i see when i google it. I thought maybe i could tap into the 5vsb wire? I am not sure if that would be a good option. Also now that u mentioned that 5vsb always supplies 5v I think that using a dual color led is out of question? I am kinda limited on space in the case so wanted to make it as simple as possible.

[AbydosOne]

On 9/9/2024 at 3:29 PM, melovesleep said:

I thought maybe i could tap into the 5vsb wire?

That's roughly what I'm suggesting, yes. The best way would be to pull right from the connector, but that would involve trimming and reterminating every wire in the harness to keep everything clean.

 

On 9/9/2024 at 3:29 PM, melovesleep said:

Also now that u mentioned that 5vsb always supplies 5v I think that using a dual color led is out of question?

That's why I mentioned some logic between the power and the LED. It could be as simple as a 7400 NAND gate IC:
 

 

V_CC = 5V_SB
GND = GND

1A = 5V
1B = 5V_SB
1Y = sink of green LED

2A = 1Y
2B = 1Y
2Y = inverted output of Y1; sink of red LED

Wire LEDs from 5V_SB, through limiting resistor, through LED, to respective Y terminal.

That's probably a little over-engineered, but that's how my brain works...

[manikyath]

6 minutes ago, melovesleep said:

I have some experience but with bigger electronics, sockets etc, but not pc components. By a harness you mean some kind of extension? Thats the only thing i see when i google it. I thought maybe i could tap into the 5vsb wire? I am not sure if that would be a good option. Also now that u mentioned that 5vsb always supplies 5v I think that using a dual color led is out of question? I am kinda limited on space in the case so wanted to make it as simple as possible.

basicly, you have this situation:

- there is a common ground, as there is with all electronics.

- you have a +5v line that is always powered, even when the system is off.

- you have the positive end of the power LED, which is either the trigger signal, the trigger signal with a current limit, +5v, or +5v with a current limit.

- you have the negative end of the power LED, which is.. you guessed it.. either the trigger signal, the trigger signal with a current limit, ground, or ground with a current limit.

 

the power on LED can just be connected between the led + and - as usual. depending on which way your motherboard is wired, the power off LED is either very simple, or needs some extra work.

 

if the LED is +5v on the positive, and the trigger with a current limit on the negative, you can just wire the off LED between the power led negative (as it's positive) and the ground. this is actually how my homemade server case uses red for off, and blue for on.

 

but realisticly, if you have some transistors on hand of both PNP and NPN variety, and 1K resistors, what you have here is a +5v rail, a ground, and a signal. from there on you can just use transistors to turn on and off whatever you like, on whichever state of the signal. the space you need to make such circuits is absolutely minimal, like.. actually, it could live on top of the front panel header (which, depending on your board, might by itself contain +5vsb and ground. it's how i wired said server.)

[Glenwing]

28 minutes ago, AbydosOne said:

That's roughly what I'm suggesting, yes. The best way would be to pull right from the connector, but that would involve trimming and reterminating every wire in the harness to keep everything clean.

 

That's why I mentioned some logic between the power and the LED. It could be as simple as a 7400 NAND gate IC:

 

That's probably a little over-engineered, but that's how my brain works...

A little bit If you're just going to invert the output from the NAND, then you don't actually need a NAND gate, you can just use a normal AND gate. And if you have an AND gate where one of the inputs is just always high (5V_SB), then you don't need an AND gate either because the output is just going to be the remaining input signal itself, so you can use run the line directly. At least, assuming that input can sink current. Theoretically in that case, all you would need is this:

 

If you wanted to sink the current to GND instead, a single P-channel FET will do it.

 

 

[melovesleep]

23 minutes ago, AbydosOne said:

That's why I mentioned some logic between the power and the LED. It could be as simple as a 7400 NAND gate IC:
 

 

V_CC = 5V_SB
GND = GND

1A = 5V
1B = 5V_SB
1Y = sink of green LED

2A = Y1
2B = Y1
2Y = inverted output of Y1; sink of red LED

Wire LEDs from 5V, through limiting resistor, through LED, to respective Y terminal.

That's probably a little over-engineered, but that's how my brain works...

This seems simple enough for me and the 7400 NAND will easily fit so i might give that a try

 

 

12 minutes ago, manikyath said:

if the LED is +5v on the positive, and the trigger with a current limit on the negative, you can just wire the off LED between the power led negative (as it's positive) and the ground. this is actually how my homemade server case uses red for off, and blue for on.

but realisticly, if you have some transistors on hand of both PNP and NPN variety, and 1K resistors, what you have here is a +5v rail, a ground, and a signal. from there on you can just use transistors to turn on and off whatever you like, on whichever state of the signal. the space you need to make such circuits is absolutely minimal, like.. actually, it could live on top of the front panel header (which, depending on your board, might by itself contain +5vsb and ground. it's how i wired said server.)

I have hard time understanding this part, i might have some experience but am not an electrician sorry

[manikyath]

4 minutes ago, Glenwing said:

At least, assuming that input can sink current.

i've considered that exact suggestion, but that's one of those things you shouldnt assume, because in theory it could lead to unexpected behavior, sinking residual current into a rail that should be down.

 

some USB devices (namely poorly designed USB hubs) do this, and in some cases it causes very weird hardware hang situations. around boot or shutdown.