Visual Basic, Arduino and a Servo

The overall plan is to end up with a Model Railway Layout which is being controlled from a Laptop computer by clicking (or pressing) buttons on some form of mimic panel displayed on the Laptop.

 The LEDs are working, so now on to getting a Servo to behave.

 Many thanks first of all to Paul McWhorter on Youtube for his series of video instructions

https://www.youtube.com/playlist?list=PLGs0VKk2DiYw-L-RibttcvK-WBZm8WLEP

Tutorials no. 30 and 31 are the ones about Servos, how to connect them and control them.

 The Visual Basic Code and Form

In VB, make up a form with 4 Buttons. 
For this simple version, we only need 2 of them.  We will ignore the "pretty coloured" ones just now!!

CW for Clockwise             ACW for Anti Clockwise

This is all the code needed for these buttons.

Private Sub Basic_AC_Click()     ' This is the code which is executed when the ACW button is used

      MSComm1.Output = "a"         

End Sub

Private Sub Basic_CW_Click()  ' This is the code which is executed when the CW button is used.

      MSComm1.Output = "c"

End Sub

Clicking on the “ACW” button sends a single character “a” to the Arduino. The serial Input in the Arduino reads this character and assigns it to a variable called Input_char

Arduino Code

The essential code in the Arduino looks like:-

          if (Input_char =='a') {servoPos = 135; myServo.write(servoPos);}              // instructs the Servo to turn to 135 degrees

          if (Input_char =='c') {servoPos = 0; myServo.write(servoPos);}                 // instructs the Servo to turn to 0 degrees

Essentially when the Arduino receives a single character “a”, then the Servo rotates anticlockwise by 135⁰  The character "c" makes it rotate Clockwise by  135⁰

These are the important lines and it now means that the Servo can be controlled by clicking buttons on a computer screen, or pressing them if it is a touch sensitive screen.

Those would be the functional lines of code and I wish it was that simple.  We need lots of extra lines however to enable communication. 

The nice thing is that having got the basics sorted, it will be a simple “Copy and Paste” job for future Programs.

VB6 Code to enable Serial Communication 

In VB6, the code to enable Serial communication will look like:-

    Portnumber = 4                               ‘sets port number as 4 – this may be different in other computers

    MSComm1.CommPort = portnumber            ‘tells the computer which is the selected Port
    MSComm1.PortOpen = True                              ‘Opens the port for Communication
    MSComm1.RThreshold = 1                                  ‘looks for a single character input
    MSComm1.DTREnable = False                           ‘I’m not quite sure what this does!!

 In the Arduino, we need additional code to enable Serial Communication as well as installing the Servo Library.

 #include <Servo.h>                    //  load up the Servo Library
 char Inpchar;                               // Single Character Input
 int servoPin=9;                           // allocates pin 9 to control the Servo
 int servoPos =00;                       // Create a Variable for the Servo position, give it a starting value of 0
 Servo myServo;                         //  Give the Servo a name

 

   // put your setup code here, to run once:

void setup() {
Serial.begin(9600);                      // Enable serial Communication

myServo.attach(servoPin);          // allocates Pin 9 to control the Servo

}

 void loop() {                                        //  This is the part of the Program that gets repeated continuously.
    if (Serial.available())                         // Check if Serial port is enabled.
    { Inpchar = Serial.read();}                // if it is enabled, then read a character.

 Once all that is done, if an Input Character is detected, these 2 lines are triggered if they are true.

if (Inpchar =='a') {servoPos = 135; myServo.write(servoPos);}              // instructs the Servo to turn to 135 degrees

if (Inpchar =='c') {servoPos = 0; myServo.write(servoPos);}                  // instructs the Servo to turn to 0 degrees

 Connecting the Servo
With this basic set up, we just need the 3 Servo cables to connect to 5V, Ground and Pin 9.

This runs fine for a single Servo, but you couldn’t use it to control too many as it would overload the Arduino.

With working Programs on the Laptop and Arduino, clicking a button on the Laptop screen makes the Servo Turn the direction selected.