why not just not strip the wires and rewire to a normal molex. Instead of putting strain on the motherboard like that.

it might work but those leds take less power than a fan. it's kinda risky in my book I bet those lights are powered by very small solid state switches. though the power led header may just be a hardwire to 5v. you may be able to verify by following traces. if so that may be safe.

at own risk 😀 personally I wouldn't risk it. but if you do, let us know how bad of an idea it was 🤣

I doubt that LED headers would power a fan, because they have to be current limited (likely through a resistor), otherwise LED would blow up instantly, because by itself it takes unlimited power.

adalbert wrote on 2021-03-22, 19:56:

I doubt that LED headers would power a fan, because they have to be current limited (likely through a resistor), otherwise LED would blow up instantly, because by itself it takes unlimited power.

correct

maxtherabbit wrote on 2021-03-22, 20:30:

adalbert wrote on 2021-03-22, 19:56:

I doubt that LED headers would power a fan, because they have to be current limited (likely through a resistor), otherwise LED would blow up instantly, because by itself it takes unlimited power.

correct

I've plugged leds into 3v batteries before without a resistor didn't seem to be shorting it. are the batteries just that slow at discharging?
can you explain this unlimited current thing? I didn't recall this.

A led is a type of diode, so if you connect it directly between Vcc and GND it will pretty much draw as much current as it is able to. And in a motherboard the PSU can output up to 20-30A on the 5V line, so it would pretty much blow instantly.

As for your experience with the battery, I guess it would depend on how much higher the battery voltage is compared to the led forward voltage, and also how much current the battery can deliver. In most cases it will probably end up burning sooner or later.

TheMobRules wrote on 2021-03-23, 02:46:

A led is a type of diode, so if you connect it directly between Vcc and GND it will pretty much draw as much current as it is able to. And in a motherboard the PSU can output up to 20-30A on the 5V line, so it would pretty much blow instantly.

As for your experience with the battery, I guess it would depend on how much higher the battery voltage is compared to the led forward voltage, and also how much current the battery can deliver. In most cases it will probably end up burning sooner or later.

interesting. 🤔 seems to make sense. thanks!

Batteries, especially smaller ones can indeed provide limited current, because they have so called internal resistance (just like they would have resistor wired in series with them). All batteries have internal resistance, but with large ones it is so small that it doesn't matter. Coin cells can have pretty high internal resistance, several ohms sometimes. Discharged or old batteries can also have higher internal resistance.

You're all correct, it didn't work 😄. I wired it into the 5v on a molex connector instead.

adalbert wrote on 2021-03-23, 11:11:

Batteries, especially smaller ones can indeed provide limited current, because they have so called internal resistance (just like they would have resistor wired in series with them). All batteries have internal resistance, but with large ones it is so small that it doesn't matter. Coin cells can have pretty high internal resistance, several ohms sometimes. Discharged or old batteries can also have higher internal resistance.

makes perfect sense.