1) what is the max draw I can draw from NodeMCU V3 logic and 5v pins? 2) Also, I heard i draw with it more than 500mA, the PC USB port stops working. Is that information actual? Because USB 3 port has 900mA and USB 2 had 500mA max

  • it is unclear what you are asking ... is what actual? – jsotola Sep 25 '19 at 7:05

for ESP8266 (which your NodeMCU is based upon) , the maximum current is about 20mA sinking and 12mA sourcing per [single] pin. so the maximum current of all GPIOs together is a lot lower than the 500mA USB limits.

you have to use external drivers (transistors, MOSFETs) for that purpose.

Sink current: the current which is provided when you pull the pin LOW. e.g. when you provide GND for the cathode of an LED. (the Anode is connected to VCC).

Source current: the current which is provided when you pull the pin HIGH. e.g. when you provide VCC for the anode of an LED. (the cathode is connected to GND).

the difference is for different internal resistance for identical N-MOS/P-MOS, due to their structure. that's why many devices like 7segment drivers, or motor drivers supply GND for the Load (common anode drivers) instead of VCC.

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    I would guess the question is not about the esp8266 io pins, but about the 3.3 V pin and the NodeMcu 3 on-board regulator – Juraj Sep 25 '19 at 8:25
  • @Juraj it is said "logic" and 5v pins. It seems he means both of them – Tirdad Sadri Nejad Sep 25 '19 at 10:35
  • In that case, the Vin pin (which provides the 5 V from the USB cable) will be limited by the power source or cable and the 3.3 V rail provided by the NodeMCU i wouldn't draw more than about 300 mA from it. I don't know the rating of the actual component but looking at the package and amount of board area for heat dissipation i think that'd be a safe value for most ambient conditions. – hooskworks Oct 25 '19 at 9:21

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