Arduino timer to turn a serve at a certain time

Question

i am working on a project for my school tech class. Our goal is to make a vehicle that will travel along a cable and drop an egg to a target while going down the cable. i am using an arduino to to open a trap door with a servo after a certain amount of time that is set by two push buttons, and a third push button will control when the timer starts. Here is my circuit enter image description here

Here is the code:

#include <Servo.h>
#include <LiquidCrystal.h>
int b = 0;
int up = 0;
int down = 0;
int val = 100;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
Servo myservo; 
int pos = 0; 
void setup() 
{
 pinMode(b, INPUT);
 pinMode(up, INPUT);
 pinMode(down, INPUT);
 lcd.begin(16, 2);
 myservo.attach(9); // attaches the servo on pin 9 to the servo object
}
void loop() 
{
 digitalRead(down);
 digitalRead(up);
 digitalRead(b);
 lcd.setCursor(0, 0);
 lcd.print("milli seconds:");
 while (b == HIGH)
 {
 digitalRead(down);
 digitalRead(up);
 digitalRead(b);
 lcd.setCursor(0, 1);
 lcd.print(val);
 myservo.write(0);
 if (up == HIGH, down == LOW)
 {
 val + 1;
 } 
 if (down == HIGH, up == LOW )
 {
 val - 1;
 }
 delay(val);
 myservo.write(100);
 delay(1000);
 }
}

• jsotola: you did not ask any questions ... you also did not say if anything is working incorrectly
• Gerben: The (pull-down) resistor on the top right button in on the wrong leg of the button.

Answer 1

in setup you are calling

pinMode(b, INPUT);
pinMode(up, INPUT);
pinMode(down, INPUT);

but b, up and down all equal 0 so this is what you are doing is :

pinMode(0, INPUT)
pinMode(0, INPUT)
pinMode(0, INPUT)

This doesn't do what you want at all, these need to be assigned to pins. All you are doing is repeatedly setting arduino digital pin 0 to INPUT 3 times.

secondly

while(b == HIGH)

will never fire since b is 0 and is never set to anything else. so it will never == HIGH

Finally,

digitalRead(down);

doesn't do anything useful; what it does is read from pin down which is set to 0, and then drops the return value on the floor

also, this,

if (up == HIGH, down == LOW)

is just very wrong, sholud be

if (up == HIGH && down == LOW)

anyway based on you scematic, fixing this code:

#include <Servo.h>
#include <LiquidCrystal.h>
const int B = 7;
const int UP = 8;
const int DOWN = 9;
int val = 100;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
Servo myservo; 
int pos = 0; 
void setup() 
{
 pinMode(B, INPUT);
 pinMode(UP, INPUT);
 pinMode(DOWN, INPUT);
 lcd.begin(16, 2);
 myservo.attach(9); // attaches the servo on pin 9 to the servo object
 lcd.setCursor(0, 0);
 lcd.print("milli seconds:");
}
void loop() 
{
 // todo: debounce the switches
 int up = digitalRead(UP);
 int down = digitalRead(DOWN);
 int b = digitalRead(B); 
 if (up == HIGH && down == LOW)
 {
 val += 1 // todo: handle overflow
 }
 if (down == HIGH && up == LOW )
 {
 val -= 1
 }
 lcd.setCursor(0, 1);
 lcd.print(val);
 if(b == HIGH)
 {
 myservo.write(0);
 delay(val);
 myservo.write(100);
 delay(val); 
 }
}

this will do what the origonal code was trying to do, more or less, but the proper way to do this would be (in psuedo-code):

// Setup pins etc.
// Setup(): pinMode(...) ... etc.
// Loop():
// debounce buttons
// handle up/down
// record milliseconds when button is pressed
// see how much time has passed
// trigger servo when timer has passed

• Mehmet Haspolat: thanks for your response but it didn't work. the servo would just move randomly and the timer didn't work it just increased and then reset and increased again.