Introduction: Controlling 3 Servo Motors With 3 Potentiometers and an Arduino
Hi there. This is my first instructable, so I hope you will be patient with me if I make any mistakes setting it up. It is written for beginners, so the more advanced among you can skip a lot of this and just get to wiring it up.
The goal I set myself was to be able to control the robot shown in this web site:
I needed to be able to control 3 different servo motors by altering the position of 3 potentiometers. There are lots of people out there doing things like this, but I couldn't find an exact match for everything I needed, so I decided to post up this instructable to bring everything I learned together in one place so that anyone else who wanted to do something like this could get it up and running quickly. This instructable is really a summary of other peoples excellent work and effort.
Before I list out the individual steps involved in this, I want to give a quick explanation of how everything works.
The potentiometers send an analog signal to the Arduino. The sketch on the Arduino (more on this later) then converts the analog input from the potentiometer into a digital output and sends this output to the servo motor which then moves left or right by the appropriate amount.
The potentiometers are powered from the Arduino's 5v line, while the servos get their power from the battery pack.
Important note: It is VERY important to ground the Arduino into the battery pack/servos to avoid nasty things from happening, but I will talk about this in more detail as we go along.
Step 1: Preparing Your Components
You need three 10k potentiometers with legs that can fit into a breadboard.
I found them here:
Next are the servo motors. I used the smallest ones as the load they would move would be very small and they were cheap.
Next you need a 4 AA battery pack:
A breadboard to connect everything up:
An Arduino Uno R3 (at least this is what I used):
A usb cable to connect the Arduino to a pc and power it:
The Arduino IDE software to upload the program that will control the servos:
Some male/male jumper cables and some jumper wire to make the connections
Breakaway header pins which will be used to connect your motors to the breadboard. I like these ones because you don't have to adjust the plastic divider to get them to fit in a breadboard.
Step 2: Prepare Your Breadboard
A lot of bread boards are split into 2 sections along the power rails at the top and bottom(which caused me a bit of head scratching when I first started using them.) By using 4 small pieces of wire you can bridge across the gap to make sure your power goes all the way across the breadboard. I finally bought one which was connected all the way across but just in case you have this problem, this is how you solve it.
Step 3: Wiring Up One Potentiometer 1
This diagram shows what the 3 pins on the potentiometer are for.
Step 4: Wiring Up the Potentiometer 2
Take 3 of the male male cables and push them into the breadboard as shown in the diagram
Step 5: Wiring Up the Potentiometer 3
Now push the pins of the potentiometer into the breadboard as shown in the diagram
Step 6: Wiring Up the Potentiometer 4
Now repeat this process 2 more times and we will now be ready to connect the signal cables to the Ardiuno
Step 7: Wiring Up the Potentiometer Final Step
Now we take the yellow signal cables and plug them into the Arduino board. Look carefully at the Arduino and you will see a part of the board called Analog In. We will be plugging our cables into A0, A1 and A2 as shown in the diagram.
For the moment that's us finished with the pots, now to get the motors set up.
Step 8: Wiring Up the Motors 1
As with the potentiometers we are going to do the same thing three times so I will talk you through how to set up one in detail and all you have to do is repeat the process.
Cable colours on motors are tricky as they vary from one motor to another. In my diagram
black is ground (-)
Red is power (+)
Yellow is signal(s)
Take a pair of long nosed pliers and break off a strip of 3 header pins and insert them into the female connector on the servo motor. Connect the servo to the breadboard as shown in the diagram. Once you have done that, we will need to connect the motors to the bottom power rails, so take two male male cables and insert them into the breadboard as shown.
Repeat this process two more times and we will then be ready to connect the motors to the arduino
Step 9: Wiring Up the Motors 2
Now we have connected the motors to the bread board it is time to connect the signal cable to the Arduino, for this you will need 3 male male jumper cables.
Plug them into the breadboard and then into the Arduino at these locations:
These are on the right hand side of the Arduino as orientated in my diagram. This is where the digital signal from the Arduino is sent to the servo to tell it how to turn.
Once this is done we are ready to hook up the power and get it working
Step 10: Adding Power
At this point we want to connect the Arduino 5v power and ground to the top rail which will give power to the potentiometers, and then we will connect our battery pack to the bottom rails to power the servos.
If we do this however it will mean the Arduino ground plane and the servo ground plane will not be connected to each other and this could potentially result in big problems. Unplug the Arduino from the USB cable, make sure the battery pack is not connected to the bread board and connect two male male jumper cables as shown in the diagram, one to the 5v in the Arduino, the other to the ground in the Arduino.
Then take a male male jumper cable and connect the ground from the top rail to the ground on the bottom rail as shown on the right hand side of the breadboard. This now ties in the Arduino ground to the battery ground which we will attach next.
Finally add the battery pack to the breadboard and we have finished the physical setup and will move onto programming the Arduino.
Step 11: Programming the Ardiuno
For anyone not familiar with loading up sketches to the Arduino I suggest taking the time to go through the tutorials here before continuing.
To review the connections in my setup
The potentiometers are plugged into A0, A1 and A2
The servos are plugged into ~9, ~10 and ~11
We will need these numbers when we write the code to get the Arduino working with our setup. Below is the code I used to get the Arduino working. It is not my code, I hacked out the parts I didn't need from someone else's code, unfortunately I can't remember where i found it so can't give credit to the person who wrote it. If you recognise it please let me know and I will put a link here to the person's project.
int potpin = 0;
int potpin2 = 1;
int potpin3 = 2;
int val = 0;
int val2 = 0;
int val3 = 0;
val = analogRead(potpin);
val = map(val, 3, 1023, 0, 176);
val2 = analogRead(potpin2);
val2 = map(val2, 3, 1023, 0, 176);
val3 = analogRead(potpin3);
val3 = map(val3, 3, 1023, 0, 175);
Paste this into a blank sketch, save it and upload it to your Arduino and you should now be able to control your servos with your potentiometers and be able to get on with your project!