# Getting 5V directly from the Anet A8 mainboard

My anet A8 stepper drivers get very hot after some time printing, so I decided to install a 5V fan to cool them down. I had the idea to get a 12V to 5V regulator to connect a 5V fan, but then i found this image:

(source: lokspace.eu)

It looks like the Anet A8 has an ICSP and Serial header that can deliver 5 or 3.3 V directly from the board. Is this correct? If it is, how many amps can i get from this pin? Can I connect a 5V fan directly here?

Thanks and sorry for my bad English.

You would be better to use a 12V fan.

The 5V is for powering logic. It should not have motor loads, even fan motor loads, applied to it. You will not be saving power over using a 12V fan. According to @Tom 's answer, the 5V is derived through a linear regulator.

A linear regulator has the property that the current drawn from the regulator at 5V will equal the current drawn by the regulator at 12V. $$7/12$$'ths of the power will be lost in the regulator chip as heat, which may cause the chip to overheat if there is not enough cooling margin in the thermal design.

If you use a 12V fan the current consumption of the fan for the same cooling capacity will be lower, and you won't waste more energy dropping the voltage.

May I ask how hot the steppers are? Too hot to comfortably hold for more than a few seconds may still be completely acceptable for motors. So hot that the plastic holding them melts is too hot for the mounting, but may still be ok for the motor. So hot that they cause burns with 5 second contact is probably too hot.

If the motors are too hot, it might be better to check the current the motor drivers are programmed to deliver (either through software configuration or a potentiometer -- I don't know the printer). Getting the current right is a better fix that managing the excess heat. It may also improve the linearity of microstepping and improve print quality.

• Stepper motors don't get very hot. Their drivers can get a little hot but I can touch the heatsink over them for more than 5 seconds without any problem. Should I still think about the additional fan? I just wanted to install it because I found more than one webpage saying that cooling the drivers would improve print quality. I also was afraid that the little heatsink that the drivers have (images.app.goo.gl/boU13KNmcH4eD9Eq8) was not enough to cool them down. @cmm – jnts Jun 29 '19 at 11:39
• Cooling electronics is always good. Period. If you can add a fan, no harm will come of it, especially if it is a fan powered from +12 V. If it improves print quality then you needed more cooling. If it doesn't, you didn't, but cooler is better and increases operating life. – cmm Jun 30 '19 at 17:26

The 5V is derived from the 12V supply by a linear regulator (L7805CD, DPAK package with 100 C/W thermal resistance). The maximum you can draw from it (without overheating the regulator) is around 200mA. Considering the electronics on the board are already using some power, the maximum would be around a 150mA fan but this would have the regulator running near its maximum limits.

5 V and 3.3 V are both logic "highs" in computing and measured against GND. If the fan simply has to know the on stance and nothing more, then you could run a fan with the logic 5 V (and probably 3.3 V for about 50% spin speed).

• This misses the issues of source impedance and thermal constraints. – Sean Houlihane Jun 28 '19 at 7:35