Controlling the fan speed with your Arduino

Intro

You savaged a fan from an old PC to use it as a ventilator? Just hook it up to 12V and the sucker runs. Well, it runs at a constant speed. Maybe too fast, maybe too noisy. There must be a possibility to slow it down.

The idea

When you apply 12 Volts to it and then remove the power supply, it keeps spinning while getting slower. So if you continuously apply and remove the power, you can control the fan of the speed by the duration of the phases when the 12V is on and when it is not.

What do we need

The Arduino doesn't supply 12 Volts. So we have to use some sort of switch. An electronic switch. A MOSFET. That's a kind of transistor, that can handle the needed current/voltage needed. I used the IRF530N, because it was the only Mosfet I had and it matches the specification of the vent by far ;-). It's a N-channel Mosfet. That means you can control the connectivity of the negative pole of the power source to the fan by applying a positive voltage.

PWM

Pulse Width Modulation is the magic phrase. A digital output pin can only have two possible states. On or off. 1 or 0. HIGH or LOW. While HIGH is typically indicated by an output of 5 Volts (3.3 Volts occasionally) is LOW represented by a 0 Volt output. So how do we simulate an output of 2.5 Volts? Well, simply spoken, if we have a time frame of 10 seconds. Half the time we put out 5 Volts and half the time 0 Volts, we will have an output of 2.5 Volts of the time of those 10 seconds. Wired? Sure. But this is how math works ;-)

PWM

Video

Wiring

 

Links
IRF530N at Amazon

PWM-Image
https://commons.wikimedia.org/wiki/User:MatthiasDD

H-Bridge for your robot

Intro

Turning a DC motor on and off isn't that much of a problem, is it? But if you want to change direction, you must have a way to switch the polarity that drives your motor. Well, that is what a H-bridge does.

How to control

For each motor, you should have 2 pins to control the output. If you pull one pin HIGH and the other one LOW the motor should spin. If you invert this configuration, the motor will spin in the other direction. Pulling both pins to LOW or both to HIGH will stop the motor.
Now you have the ability to turn the motor on in both directions. If you also want to control the speed of the motors, you should connect it to PWM ports.

Wiring

Video 

Pro-Tip

If your motor doesn't spin, you probably have a too low input voltage. These boards are equipped with voltage regulators. So you can try using a higher voltage. I used a 9V battery for the 5V motors myself. Worked perfectly.

For controlling your robot it makes sense to extract the commands for the wheel to spin in separate methods. Make a method for spinning the left wheel in clockwise direction. And one for counterclockwise direction. It's so easier to program some logic to your vehicle.

Buy at Amazon

H-Bridge L298N
5V DC Motor with gearbox
Robot chassis with motors
H-Bridge L9110