This is an Android app which reads ANT bike speed sensor in the background, and sets fan speed automatically based on current wheel speed.

I use this when riding indoor on a bike trainer with my ANT enabled Samsung phone.

I used a RPi4 connecting to a RC servo, which then controls the rotary knob on a cheap fan in front of my bike. This Android app then reads current wheel speed through ANT from the sensor on my bike, and sets desired servo position to turn off, turn to low, and turn to high fan speed.

I wish I had a programmable fan which can better simulates the headwind when cycling indoor.

In addition to this app, I also run Zwift Android app on the same phone, reading the same bike speed sensor from my bike.

I have to create a Foreground Service because Zwift app (not the Companion) obviously puts a lot of stress on my 3-year-old S8 and the runtime keeps on killing my Service.

I use an analog RC servo retired from my 1/8 electric buggy, so it is quite strong without taking too much current from the 5v pins on my RPi4.

I should've found a better way to turn the knob with the servo arm but this is what I've got so far over the weekend.

See my go-servotester project for more detail about RC servo control.

I have a 13 years old Cycleops Fluid2 so I have to attach a speed sensor on it for Zwift. Sadly I don't have power meter either. The ANT speed sensor is an old Garmin one. Without a USB ANT stick, this leaves me with the only choice to use my ANT enabled Samasung phone to control the fan.

For ease of use (and personal use only) I created a HTTP server so I can simply send a HTTP GET to the endpoint, specifying the correct pin (I use pin 11) to control the RC servo.

Example control command:

Set servo position to 85% (endpoint 1.0ms to 2.0ms PWM, the usual range of a RC servo) curl http://192.168.1.111:8080/servo?pin=11&pos=85