I'm currently modding a 3D printer (Anet E10) by upgrading it's fan to a powerful 3.4A 12V fan. It's model is 9BMB12P2K01. The current layout on it's PCB does not allow such a powerful fan to be connected directly to it's designated MOSFET because it looks like it can't handle more than 1A safely. I can't take the motherboard apart to see the actual circuitry for the fan control. My assumption is that the CPU (Atmega2560) uses a PWM signal for the fan control.
The standard fan cable plugs into a 2 pin socket connector (this type). By what I was able to measure, there is 0 resistance between the positive pin of the connector and the positive side of the power supply. There is infinite (or at least > 200 ohm) resistance between the negative side of the connector and the negative side of the power supply (GND). I am not experienced with MOSFETs, so I cannot identify it's type or layout. Judging by this measurement, the actual "PWM" is happening on the negative pin.
The powerful fan in question requires a PWM signal on a special pin. Thus, my question becomes:
- What type of MOSFET is on the board? Is it an N-type, or a P-type? (it's covered by heatsink I cannot take off)
- How can I use this (possibly) existing PWM signal on the negative pin as an input to the control pin of the powerful fan?
Edit: The powerful fan will be connected directly to the power supply, leaving it's control on the control pin. It expects a PWM signal on the control pin.