09
Motors
I hope you are feeling well because we are about to learn one of the most profound and crucial components to building a robot and impressing anyone.
THE DC MOTOR
tHE DC MOTOR EXPOSED
DC Motors make the world go round.
A DC motor simply put, is a constant struggle, a battle of momentum.
Take the above diagram for example.
The schematic symbol, like the servo, is usually just a circle that says "motor" or "dc motor", etc.
There are several ways to set up a motor like this but their operation is all generally the same concept.
Here we have a magnetic field setup already in the outer magnet layer.
It is color coded to show you North and South.
Think of a magnetic field as an electric field, a constant swirl of electricity like a tornado.
If you stuck a metal pin near it, the sticky electrical tornado would grab the surface of the metal pin and push it toward the middle.
It's saying, "Come here, and find peace ye troubled soul."
Ok.
Electricity is said to flow in one direction but don't worry too much about that right now.
Now we make 1 simple wire coil and stick that in the middle.
It is color coded as well. See the blue and red?
Our outside electrical source (battery) will flow through this and interact with the already existing electrical motion which we call magnetism.
How do we get the electrical source to flow through the coil?
We could just attach the positive part of a battery to one end and the negative to the other.
Ok. "Job's done." Maybe it moved a little.
But now its stuck.
We need to try something else.
Let's swap the wires around.
OH! OH! It moved again!
What if we could make the coil swap positive and negative ends constantly? Then it would maybe keep moving, right?
That is where some geniuses long ago discovered they could attach those two ends of the coil to a cylindrical metal tube.
The metal tube needed to be attached to the power source so the electricity could flow to the coil, right?
How do we do that without it spinning the power source with it?
We don't want our battery flopping around all over the place...
They figured out they could attach brushes which could conduct the electricity to the metal tube.
Those brushes could be connected to the wires from the power source! WOW!
Later, they even implemented springs to help push the brushes firmly against the metal tube.
Then another long cylindrical tube could be stuck in the middle of that bigger rotating cylinder and that longer tube is what we attach a gear to.
BOOM!
What is happening is the positively charged coil end is pushing and being pushed through the positively charged magnetic field (remember I refer to it as electric, it just makes it easier to understand really, its not my original idea, there have been many great minds who have suggested this long ago and it makes sense to me).
The negative end of the coil pushes through the negatively charged field of the magnet at the same time.
The shift of each coil end from positive to negative and vice versa allows continuous motion.
This blew my mind and deserves a great deal of gratitude that most of the world will never even think about.
The motor can now constantly spin because when it reaches the resting point, the point where it no longer moves the coil the polarity shifts from positive to negative and on the opposite side negative to positive and so on.
Just study the diagram and you WILL understand!
DC Motors are a cheap and useful machine to attach to gears and make something like an RC car or robot move.
You can control when the power is given to the motor by hooking it up to a microcontroller pin and setting up code that outputs voltage and current when you press a button or joystick.
You can even program PWM so that it slowly revs up instead of spinning out.
You could also just hook the motor up manually without a microcontroller like you see in toys and mini fans.
If you have one lying around, Open it up! Take a look at the components inside.
There is likely a capacitor, a switch or button, a power source, maybe a resistor and the motor itself.
Try to draw this schematic out by yourself! Get some practice in. It will be worth your time. I promise!
While there is much much more to motors and gears, this should be enough for you to get started. DC motors should not be used for high precision projects, stepper motors would be more useful for those.
We will cover more advanced motor topics after you build your first robot.
Pop Quiz
1. Design a schematic with a dc motor, battery, diode, and capacitor.
2. Include an N-type MOSFET in that schematic.
3. Explain how a DC motor spins.
Get my favorite books on programming AVR chips I use.
Equip yourself with the most dependable, no hassle, quality usb programmer I use daily.
Make sure you have a basic kit. Arduino is fine, it contains the removable AVR 328p chip we will use.
I started with something very similar.
Summary
You can now start to grasp the complexity of a simple DC motor.
It is a profound little device that can be found everywhere.
Remember there are other types of motors which we can learn later.
One particularly useful one being the stepper motor which is very accurate, is used in 3D printers and high precision projects. More on that later. For now, keep building up those fundamentals!
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