I want to build an occupancy indicator with an ultrasonic sensor. I'll tell you what I want to achieve, and if anyone knows how to do this, please let me know because I don't have any coding experience.
Components:
Arduino Uno
Ultrasonic sensor
RGB LED module
The ultrasonic sensor will be placed on the door frame, and I want it to work like this:
When it detects close distance (let's say less than 10cm), to deactivate the sensor for 1 minute, and turn the RGB LED Red.
When it detects distance less than 10 for the second time, the sensor should be deactivated for 1 minute, and the RGB LED set to Green again.
Code:
(with this, the LED is green, and turns red whenever I put my hand in front of the sensor:
#define echoPin 2 // attach pin D2 Arduino to pin Echo of HC-SR04
#define trigPin 3 //attach pin D3 Arduino to pin Trig of HC-SR04
// defines variables
long duration; // variable for the duration of sound wave travel
int distance; // variable for the distance measurement
int red_LED = 10;
int green_LED = 9;
void setup() {
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(red_LED, OUTPUT);
pinMode(green_LED, OUTPUT);
Serial.begin(9600); // // Serial Communication is starting with 9600 of baudrate speed
}
void loop() {
//==============================================================
// ULTRASONIC SENSOR
//==============================================================
// Clears the trigPin condition
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin HIGH (ACTIVE) for 10 microseconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
// Displays the distance on the Serial Monitor
Serial.print("Distance: ");
Serial.print(distance);
Serial.println(" cm");
//==============================================================
// OCCUPANCY CODE
//==============================================================
if (distance < 10) {
analogWrite(red_LED, 255);
analogWrite(green_LED, 0);
}
else {
analogWrite(green_LED, 255);
analogWrite(red_LED, 0);
}
delay (1000);
}
Hello Larry, thank you for your help, I understand basic code, but I don't know how to write complex expressions myself, It's not my main job, I do this as a hobby.
Seems fairly straightforward. In the setup section, turn the red LED on and instantiate an int toggle=0; and then in the loop, if you get a <10cm result, toggle the color of the LED. Something like this:
if (distance < 10) {
analogwrite(red_LED, toggle*255); // should turn RED off in first pass thru loop
if (toggle == 1) toggle=0; else toggle=1;
analogwrite(green_LED, toggle*255); // should turn GREEN on in first pass
delay(60000); // wait one minute before checking sensor again
}
I think a large part of the problem with the code in #10 is that you have two variables for the door state. If a door is open, it's not closed. If it's closed, it's not open. So to maintain two of them is bound to create confusion and errors.
Also if you want to do this with a flag 'isDoorOpen' you should make it a bool variable and assign it values of 'true' and 'false' instead of '0' and '1'. The readability itself will help avoid errors.
Not sure you'd get the behavior you want from that code.
How about this?
// in setup create
bool pressed = false;
// in loop
void loop {
distance = readultrasonic();
pressed = readbutton();
if distance < 10 {
if (pressed) {
buzz(3);
pressed=false;
}
updateLEDS();
}
}
int readultrasonic() {
// your read from the ultrasonic sensor goes here
// always returns an integer, whether the sensor yields one or not
// if the sensor yields a non-integer result because nearest object is out of range
// of detection, then return 11 (so the LEDs and buzzer won't trigger).
}
bool readbutton() {
// your button checking code goes here
// always returns false unless button is pressed
}
void updateLEDS() {
// your LED toggling code goes here
}
void buzz(int numbuzzes) {
// loop and buzz as many times as indicated by numbuzzes value
// if you want to up your game, test for a button press after every buzz
}
The sensor toggles the LED when I pass my hand over it, so it works fine, the push button is connected and it shows 1/0 when pressed, and the buzzer is connected and working, so everything works individually, but I don't know how to put them together, looks impossible to me since I got an error at almost every move I make.
If you really can't assemble that, you're essentially asking someone to code for you. You should either post specific attempts, along with the specific compiler error output, or else pay someone to do it.
By the way, so far I have not seen any variable to keep track of what event is "next time". In your description you talk about an alternating sequence but the program can't know what the previous state was without storing it somehow.
If your sketch is working, what more did you hope to achieve? Seems good for a beginning coder!
If I might suggest, read up on how to segment your code into Functions. It will help readability and debugging. Check out a basic tutorial here.
In the sample code I gave you (above), you will see how I suggested you might move your code into Functions. With them, most of the details are abstracted from the main Loop code, making that much easier to understand.
