I prefer to use an Arduino with a Motor Controller over say a Raspberry Pi with a motor-controller. I believe the Arudino has better support for dedicated Real-time software vs. the Raspberry Pi and as a superior platform for general computing including running Control Software. This is how we do it on the West side …
Whenever started to build a mobile robot and first started this project I set out to pick up motor controller and a platform to buildMy Tom’s vehicle around. The two most on his choices at least to me were a Raspberry Pie or an Arduino. As I found out selecting either platform I choose it would have been a bad idea, and here is why.
I eventually realized that neither platform, the Raspberry Pie nor the Arduino had everything I really wanted. The Arduino certainly lacks a robust development environment, which Is great for getting started programming embedded devices, but hardly sufficient for Somebody that makes a living programming.
Niether one will Cut it
The Raspberry Pi hardware and Linux OS are not well suited for an “embedded real time” system. But does offer an endless choice of development environments.
Leave our Options Open
It became clear, that neither platgorm would be ideal for my general development plans. Neither of them were ideal to solely commit to.
However, if I could combine them, I could get quite a bit further, by having access to the advantages that both worlds?Add
Before I get into any detail on these “hobby” controllers is
What are the first things to consider when developing a mobile robot Is how you’re going to make it move, and that is typically using motors. The cool thing is that inexpensive electrical motors are plentiful, however putting them to good use is a bit complex, Here we will conquer some of that complexity.
We will consider the following 3 things:
- What type of motor(s) do we need?
- How are we going to power them?
- How are we going to control them?
TLDR - Summary
I have settled on the Adafruit MotorSheilds for Arudino and Raspberry Pi as general purpose options. At the moment, my ideal setup involves a RPi as the controller with an I2C or SPI connection to an Arduino with a MotorController.
But not for every circumstance. It always depends on the application, having said that, let me explain what I have found (very little) so far with inexpensive electric motors…
Project Requirements
First let me frame this discussion, I am strictly talking about cheap DC motors (not AC that plug into the wall like a washing machine) that can be had for less than $10USD, often less than $1 or found in scrap electronics.
The first three motor types I discovered are the ubiquitous: DC brushed motor, toy servos and stepper motors. Incase you are uninformed like I was in early 2018..
Select Motors and Motor Controller
The purpose of this project is to select the motors and the corresponding motor controller we need to control our vehicle. The motorshield will come as an attachment to a micro controller of some sort, which happens to be either an Arduino or Raspiberry Pi, in my case.
Brushed Motors Move Wheels
In a nutshell, the brushed motors we’ll use to turn the wheels of the vehicle, they have the advantages of being easily controlled (speed up, slow down, stop) with just two wires (+ and -), the direction of the motor can be changed simply by reversing the current to the motor.
They are also really cheap and can be found every where, including scrap electronic toys and utilties.
Servos to Pan and Tilt Camera
We will include two inexpensive servos onto the vehicle to handle the pan and tilt camera functions.
Drive Train
Moving the vehicle is one thing, steering it is a whole nother thang. Fortunantely for us, we are going to adopt the fine art of skid steering, the age old method of how the caveman commutted back in the day.
Skid Steering
My primary vehical is a 4wd, that is 4 DC motors directy spinning two rubber tires. I also have available two, two wheeled vehicals and a train tracked vehical.
In all cases each of these vehicle employ skid steering on account a one wheel (wheels or tread) will be skidding along when your turnin.
TODO ~ Create a skid steering page
Of course, you can get real fancy and spin the thing on axis by employing equal forces of forward and reverse on opposing sides of the vehicle. Which does have significant advantages in tight areas such as those found in long corridors, warehouses and such.
Required Motors and Controller
We need to power the following motors (at minimum):
- 4 DC Motors
- 2 Servos
Cut to the chase, the Adafruit XXXXX Arduino motor controller, and the sister Adafruit YYYY stepper motor controller for the Raspberry Pi are two such controllers that suite our purposes perfectly well.
Which MicroController (MicroComputer)?
Todo has a discussion of using a Raspberry Pi + MotorController or Arduino + Motor Controller.
Alternative Shields
Adafruit Sheild v1 & v2
Adafruit essentially has two versions of their MotorShield v1 and now v2. …
Version 2 I2C
Version 2 of the AFMS runs over the I2C bus.
OSEPP Shields v1 & v2
The OSEPP MotorSheilds effectively duplicate the functionality of the Adafruite MotorShields.
The documentation is hard to find and must be pieced together through the documentation of their hardware kits. I do find the hardware to be of a sturdy make. The use connectors to help in learning, the Adafruit are more through for real prototyping.
Motor Software
Adafruit software for Arduino MC and Raspberry Pi MC.
MQTT and Motor Control Channel
Connect the motor controller to the MQTT control channel. NOTE: on vehicle may use the motor control channel when availble, however, must always be able to regain control (or shutdown completely) if the control channel has been lost.