limit switches within a counter

Question

Hi folks,

Im a technology teacher in Scotland and the powers above have decided that we move from our old PBASIC run Stamp boards, and use Arduino. It has also been decided this will start of next month! this means during my holidays I have been left with no choice but to learn the language and how it works myself, but to create a scheme of work for my pupils to follow. Most of what Ive done is based on Jeremy Blums brilliant online tutorials , and things that are different I was mostly able to work out by looking up.

I have came across a problem though and for the life of my I cant seem to solve it and I was hoping someone on here could help! Ive designed a project of dancing ballerina toy (my feeble attempts to try and get more girls into Engineering). When a master switch is pressed, it will put on an ultabrite LED to act as a spotlight for the dancer. The ballerina will then "dance" by sitting on top of a turntable that will rotate one way until it hits a limit switch. When it hits this limit switch it will rotate the other direction until it hits another limit switch, sending it back the original direction. This dancing will repeat 5 times, then everything will switch off.

This is a flowchart of what I'm attempting to do, which will hopefully make things a little clearer:

This is how I have wired up my Arduino Uno:

and this is my attempt at the code. It was originally more complicated added in debouncing and commands to keep outputs on once the switches have been presssed, but I deleted all that to try and work out what is going wrong.

/*

dancing toy System

*/

int MasterSwitchPin = 13; // Master switch

int LeftSwitchPin = 12; // Makes motor turn left

int RightSwitchPin = 8; // Makes motor turn right

int Motor1APin = 7; // H-bridge leg 1

int Motor2APin = 6; // H-bridge leg 2

int LEDPin = 2; // LED

void setup()

{

Serial.begin(9600);

pinMode (MasterSwitchPin, INPUT);

pinMode (LeftSwitchPin, INPUT);

pinMode (RightSwitchPin, INPUT);

pinMode (Motor1APin, OUTPUT);

pinMode (Motor2APin, OUTPUT);

pinMode (LEDPin, OUTPUT);

}

void loop()

{

if (digitalRead(MasterSwitchPin) == HIGH)

{

digitalWrite(LEDPin, HIGH);

}

Serial.print("button pressed LED on");

for (int counter = 1 ; counter <= 5; counter = counter +1)

{

while (digitalRead(LeftSwitchPin) == HIGH)

{

digitalWrite(Motor1APin, HIGH);

digitalWrite(Motor2APin, LOW);

Serial.print("motor goes one way");

}

delay(1000);

while (digitalRead(RightSwitchPin) == HIGH)

{

digitalWrite(Motor1APin, LOW);

digitalWrite(Motor2APin, HIGH);

Serial.print("motor goes the other wat way");

}

delay(1000);

}

Serial.print("repeated 5 times");

digitalWrite(LEDPin, LOW);

digitalWrite(Motor1APin, LOW);

digitalWrite(Motor2APin, LOW);

Serial.print("switch everything off");

}

can anyone help me please and fix my code? thanks in advance!!!

shabaz · Accepted Answer

Hi Paul, I don't think any debouncing is needed, so the first code is more usable I think. I modified it slightly (created #define to clean it up, and rearranged the location of code so the loops are a bit cleaner): /*
dancing toy System
*/

int MasterSwitchPin = 13; // Master switch
int LeftSwitchPin = 12; // Makes motor turn left
int RightSwitchPin = 8; // Makes motor turn right
int Motor1APin = 7; // H-bridge leg 1
int Motor2APin = 6; // H-bridge leg 2
int LEDPin = 2; // LED

#define LED_ON digitalWrite(LEDPin, LOW)
#define LED_OFF digitalWrite(LEDPin, HIGH)

#define MOTOR_LEFT digitalWrite(Motor2APin, LOW);digitalWrite(Motor1APin, HIGH)
#define MOTOR_RIGHT digitalWrite(Motor1APin, LOW);digitalWrite(Motor2APin, HIGH)
#define MOTOR_STOP digitalWrite(Motor1APin, LOW);digitalWrite(Motor2APin, LOW)

#define BUTTON_PRESSED (digitalRead(MasterSwitchPin) == HIGH)
#define END1_HIT (digitalRead(LeftSwitchPin) == HIGH)
#define END2_HIT (digitalRead(RightSwitchPin) == HIGH)

void setup()
{
 Serial.begin(9600);
 pinMode (MasterSwitchPin, INPUT);
 pinMode (LeftSwitchPin, INPUT);
 pinMode (RightSwitchPin, INPUT);
 pinMode (Motor1APin, OUTPUT);
 pinMode (Motor2APin, OUTPUT);
 pinMode (LEDPin, OUTPUT);
}

void loop()
{
 LED_OFF;
 while(!BUTTON_PRESSED); // wait here until the button is pressed
 LED_ON;
 Serial.print("button pressed LED on");
 for (int counter = 1 ; counter <= 5; counter = counter +1)
 {
 MOTOR_LEFT;
 Serial.print("motor goes one way");
 while (!END1_HIT)
 {
 // do nothing, just delay a very tiny amount
 delay(10);
 }
 MOTOR_STOP; 
 delay(1000);
 
 MOTOR_RIGHT;
 Serial.print("motor goes the other way");
 while (!END2_HIT)
 {
 // do nothing, just delay a very tiny amount
 delay(10);
 }
 MOTOR_STOP;
 delay(1000); 
 } // end of for loop

Serial.print("repeated 5 times");
} I have no idea if the code will work (I don't have an Arduino) but I suspect it is closer to what is needed. Could you give it a test, or at least test a modified version of this, so that you can confirm the #define lines do what is expected, and then the program logic can be ironed out. The exclamation marks indicate boolean NOT by the way. Also, I'm not sure the circuit is correct. I think pin 1 of that integrated circuit needs to go somewhere - can you connect it to the positive supply? Also, the LED is connected with one end to +ve according to your diagram, so by default the LED would be lit if the output is LOW. I've taken that into account in the code, so that the #define LED_ON writes LOW to the pin, and LED_OFF writes HIGH to the pin. Also, it is fairly mandatory to have a large-ish capacitor (maybe 100uF) and a 100nF capacitor across the supply rails very close to the motor control IC, i.e. directly near pin 4 and pin 8. Finally, your motor controller may be causing effects to the supply rail, causing unexpected behaviour from the Arduino. To eliminate that during testing, you need a separate supply for the motor controller (i.e. disconnect pins 8 and 16 of the IC, and feed a separate battery +ve supply to those pins, and connect the battery -ve to the ground. EDIT: corrected a few things in the code and text.

shabaz · Answer

Hi Paul,

Hopefully someone may respond sooner with better info (busy day for me today unfortunately for the next few hours, so this is a quick reply), but I had a few questions/suggestions:

1. What is the current symptom? Does any of it function, e.g. does LED turn on, does it stay on, etc. Does button detection work? Does the motor appear to get energised slightly?

2. Could you try powering the SNxxx chip from a separate supply, not from the Arduino board supply? To see what happens?

3. Could you place a 100uF capacitor across the supply rails close to the SNxxxx chip, and also a 100nF capacitor across the supply rails close to the chip too?

shabaz · Answer

Also,

Just noticed, you've got the digitalWrite commands in the while(digitalread...) statements, but you can move them to just above. The digitalWrite is sustained indefinitely until you do another digitalWrite to the same pin.

Also, before each delay(1000) line, you need to do a digitalWrite that will switch off the motors, so that for the 1000millisec delay, the motors are not moving.