The gravity fan has 3 pins. I connected one pin to the ground, one pin to the digital pin numbered 2 on ESP8266. I uploaded this code but the fan doesn't run at all. The fan supposedly uses a 5V power supply but the ESP8266 only supplies 3.3V. Could this be the problem?

void setup() {
  pinMode(2, OUTPUT);

void loop() {
  digitalWrite(2, HIGH);
  • If the fan needs 5V power you need to give it 5V power. 3.3V logic is not 5V power. – Majenko Apr 23 '17 at 18:41
  • 4
    Don't power stuff from I/O pins. An LED may work, but a fan will require too much power and also has a possibility to generate power (when turned by hand/wind) and may damage the pin. – Paul Apr 24 '17 at 6:40

The ESP can only supply 12 milliamperes of current. The fan most likely uses a whole lot more. You could for example uses a transistor to turn on the fan.

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