How to stop being controlled by your DC motor: reverse the roles!

PART 1 — Direction control

Simon BDY
Simon BDY
Jan 15, 2018 · 6 min read

This post is dedicated to anyone who is curious about the basics of DC motors in robotics, and precisely how to control them. You can begin with the previous post dealing with the different kinds of motors used for robotic applications. While some of them are not often used, some others, as the DC brushed motor, are more common.
Be aware that in this post, the word motor will be actually a short for DC brushed motor.

Today, I’m talking to you about the basics of how to control your motor.

Direction control

As I said earlier, if you plug the positive wire of your battery on one of the motor’s terminal, and the negative wire on the other motor’s terminal, the motor rotates in one direction. If you switch the wires, it rotates in the other direction. On the next images, U are batteries and M are motors.

U1 and U2 are turned upside down, reversing the polarity. M1 rotates in a direction, M2 in the other.
All these wires…
Look! Is it a bird? Is it a plane? No, it’s an H!
There is no current flowing in the grey wires, because their “doors” are closed, i.e. no contact.
There. Take a deep breath.
NPN transistor (symbol and drawing). C stands for Collector, E for Emitter and B for Base.
  • The microprocessor sends high or low signals to the H-bridge (again, easier with a controlling board).
  • The H-bridge orient the voltage so that the connected motor can rotate the way you politely asked it.
This picture is incomplete, because only direction signals are shown. We will complete it with speed signals later.


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