Smart Home: Build your own fan control with ESP8266, PWM, potentiometer and WLAN

If you want to be as professional as possible for the video chat in the home office, it is better to connect a system camera such as the Sony 6300 to the computer using an HDMI grabber instead of a webcam. It’s just stupid when the camera tends to overheat and switches itself off after twenty minutes on hot summer days. Even a slight flow of air prevents death from heat, for example from a 5-volt fan, which conveniently draws power from the computer’s USB port. With the adapter cable included with the fan, the fan turns up to an unnecessarily roaring 2400 revolutions per minute and thus interferes with the sound recording. A control system provides a remedy, and modern fans – whether with 5 or 12 volts – bring the necessary electronics with them. Four cables end in the plug that hangs from the housing: on the far left ground and power supply (depending on type 5 or 12 volts), at position 3 a speedometer signal to measure the speed. The fan pulls the connection to ground once with each rotation. The highlight is hidden in the fourth cable, on which modern fans accept a pulse-width modulated signal (PWM) (according to the specification with 25 kHz). There you set the speed from 0 to the highest possible speed that the fan can create using the length of the PWM pulses and you don’t even have to use the voltage level of the supply voltage. This means that fans with 4 connections can be controlled with microcontrollers that work with 3.3 volts without level adjustment.
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