Button Relay Control

Question

How can I fix this sketch to make it so that once the button is pressed, it performs some action for a certain amount of time and then returns back to a low state until it is pressed again. For example, I need to run a pump for 5 seconds when the button is pressed and then turn off automatically. And then, when I press the button again it will repeat, etc. I am not trying to use a relay module if it is not necessary. Here is my current sketch and a Lab View of the components:

My Sketch

#include <LiquidCrystal.h>
#include <SoftwareSerial.h>
int switchPin = 8;
int ledPin = 13;
int buttonPresses = 0;
boolean lastButton = LOW;
boolean currentButton = LOW;
boolean ledOn = false;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup()
{
 Serial.begin(9600);
 pinMode(switchPin, INPUT);
 pinMode(ledPin, OUTPUT);
 lcd.begin(16, 2);
}
boolean debounce(boolean last) //just a debounce function
{
 boolean current = digitalRead(switchPin);
 if (last != current)
 {
 delay(5);
 current = digitalRead(switchPin);
 }
 return current;
}
void loop()
{
 {currentButton = debounce(lastButton);
 if (lastButton == LOW && currentButton == HIGH)
 {
 ledOn = !ledOn;
 buttonPresses++;
 lcd.clear();
 lcd.print("Number of Button ");
 lcd.setCursor(0,1);
 lcd.print("Presses = ");
 lcd.print(buttonPresses); 
 }
 lastButton = currentButton;
 digitalWrite(ledPin, ledOn);
 }
}

THANK YOU!

Answer 1

This code should work. You will need to declare the following variables:

• lastPress // The last time the button was pressed
• outputState // The state of the timed output
• outputPin // The pin number for the timed output
• PERIOD // The amount of time that the outptu remains on

The code:

void loop()
{
 currentButton = debounce(lastButton);
 if (lastButton == LOW && currentButton == HIGH)
 {
 ledOn = !ledOn;
 buttonPresses++;
 lcd.clear();
 lcd.print("Number of Button ");
 lcd.setCursor(0,1);
 lcd.print("Presses = ");
 lcd.print(buttonPresses);
 outputState = HIGH;
 lastPress = millis(); 
 }
 if (outputState && ((millis() - lastPress) > PERIOD))
 {
 outputState = LOW;
 }
 digitalWrite(outputPin, outputState);
 lastButton = currentButton;
 digitalWrite(ledPin, ledOn);
}

A relay should be used to drive a pump etc.. The Arduino Uno can only drive 5V at maximum 20mA.

• tyler a: okay so I have tried what you mentioned and have been unable to get it to run? The variable lastPress would be akin to my variable lastButton, outputState to ledOn, and outputPin, to ledPin. I am unsure how I can declare the variable PERIOD to have a time dependent value.
• sa_leinad: PERIOD can be defined in two ways: const int period = 3000; // 3 seconds or #define PERIOD 3000 //3 seconds
• sa_leinad: The if statement I have added in my answer measures the time elapsed and compares if it is larger than the period variable. If it is it will turn the output off. More info: arduino.cc/en/Tutorial/BlinkWithoutDelay and here: arduino.cc/en/Reference/Millis
• tyler a: Appreciate all the help