Hello, new to Arduino.
I am using this photo eye.
If the sensor is detecting an object for > 10 seconds, I would like for it to turn on an LED. I am OK with the wiring but am not sure how to write the code. I believe that I will need to use a timer function? If the sensor is turning on/off every couple of seconds, I'd like the LED to remain off, but if it is sensing an object for > 10 seconds, LED goes on. Thank you.
Welcome to the group.
Always show us a good schematic of your proposed circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.
Show us your attempt at writing the code.
Draw a flow chart of your idea, put it in words...
Then put your words into a program.
Using millis() for non-blocking timing tutorials:
Blink without delay().
Blink without delay detailed explanation
Beginner's guide to millis().
Several things at a time.
Thank you for the feedback. Here is my code so far:
const int MOTION_SENSOR_PIN = 7; // Arduino pin connected to the OUTPUT pin of motion sensor
const int LED_PIN = 3; // Arduino pin connected to LED's pin
int motionStateCurrent = LOW; // current state of motion sensor's pin
int motionStatePrevious = LOW; // previous state of motion sensor's pin
unsigned long startMillis; //some global variables available anywhere in the program
unsigned long currentMillis;
const unsigned long period = 5000; //the value is a number of milliseconds
void setup() {
Serial.begin(9600); // initialize serial
pinMode(MOTION_SENSOR_PIN, INPUT); // set arduino pin to input mode
pinMode(LED_PIN, OUTPUT); // set arduino pin to output mode
startMillis = millis(); //initial start time
}
void loop() {
motionStatePrevious = motionStateCurrent; // store old state
motionStateCurrent = digitalRead(MOTION_SENSOR_PIN); // read new state
currentMillis = millis();
// if (currentMillis - startMillis >= period) //test whether the period has elapsed
//{
//digitalWrite(LED_PIN, !digitalRead(LED_PIN)); //if so, change the state of the LED. Uses a neat trick to change the state
// startMillis = currentMillis; //IMPORTANT to save the start time of the current LED state.
if (motionStatePrevious == LOW && motionStateCurrent == HIGH && currentMillis - startMillis >= period) { // pin state change: LOW -> HIGH
Serial.println("Motion detected!");
digitalWrite(LED_PIN, HIGH); // turn on
//startMillis = currentMillis;
// }
}
else
if (motionStatePrevious == HIGH && motionStateCurrent == LOW) { // pin state change: HIGH -> LOW
Serial.println("Motion stopped!");
digitalWrite(LED_PIN, LOW); // turn off
}
}
It...kind of works. If I place my hand in front of the sensor for 5 seconds or more, the LED will go on AFTER I remove my hand. I'd like for it to go off as soon as it hits 5 seconds. I also have to work out how to reset the timer. It also doesn't require a consecutive 5 second count. I can place my hand for 1 second, remove it, 1 second hand, five times and the LED will go off. Any guidance? Thank you.
Always show us a good schematic of your proposed circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.
Review what is done in this example.
Add to or remove code as needed.
//
// Version YY/MM/DD Comments
// ======= ======== ========================================================
// 1.00 22/08/25 Running code
//
//
#define CLEAR HIGH
#define DETECTED LOW
#define ledON HIGH
#define ledOFF LOW
enum FlagStates {ENABLED, EXPIRED, DISABLED};
const byte heartbeatLED = 13;
const byte MOTION_SENSOR_PIN = 7;
const byte LED_PIN = 3;
FlagStates motionFlag = DISABLED;
byte lastMotion = CLEAR;
unsigned long heartbeatTime;
unsigned long sensorTime;
unsigned long motionTime;
const unsigned long period = 5000;
// s e t u p ( )
//********************************************^************************************************
void setup()
{
Serial.begin(9600);
pinMode(MOTION_SENSOR_PIN, INPUT_PULLUP);
pinMode(LED_PIN, OUTPUT);
pinMode(heartbeatLED, OUTPUT);
} //END of setup()
// l o o p ( )
//********************************************^************************************************
void loop()
{
//********************************* h e a r t b e a t T I M E R
//is it time to toggle the heartbeatLED (every 500ms)?
if (millis() - heartbeatTime >= 500ul)
{
//restart this TIMER
heartbeatTime = millis();
//toggle the heartbeatLED
digitalWrite(heartbeatLED, !digitalRead(heartbeatLED));
}
//********************************* s e n s o r T I M E R
//is it time to check the sensors (every 50ms)?
if (millis() - sensorTime >= 50ul)
{
//restart this TIMER
sensorTime = millis();
checkSensors();
}
//********************************* m o t i o n T I M E R
//is the TIMER enabled ?
if (motionFlag == ENABLED)
{
//has the interval expired ?
if (millis() - motionTime >= period)
{
//we have finished with this event
motionFlag = EXPIRED;
Serial.println("Motion TIMER has expired");
digitalWrite(LED_PIN, ledON);
}
}
//*********************************
//other non blocking code goes here
//*********************************
} //END of loop()
// c h e c k S e n s o r s ( )
//********************************************^************************************************
void checkSensors()
{
byte currentState;
//********************************* MOTION_SENSOR_PIN
currentState = digitalRead(MOTION_SENSOR_PIN);
//did the sensor change state ?
if (lastMotion != currentState)
{
//update to the new state
lastMotion = currentState;
//if we are not timing, is there an object ?
if (motionFlag == DISABLED && currentState == DETECTED)
{
Serial.println("Detected");
//enable TIMER
motionFlag = ENABLED;
//reset this TIMER
motionTime = millis();
}
else
{
Serial.println("Clear");
//disable TIMER
motionFlag = DISABLED;
digitalWrite(LED_PIN, ledOFF);
}
} //END of this sensor
//*********************************
} //END of checkSensors()
//********************************************^************************************************
This accomplishes exactly what I was looking for. I am going to try and understand what the code is actually doing. Appreciate it!
I got this code proven out with small LEDs but am now looking to use an industrial grade LED that requires 18-24VDC. I understand Arduino does not play nice with high voltages - is this where I need to incorporate a MOSFET? I am a little confused on the differences between relays, MOSFETs, and transistors...
Give us a link to the LEDs.
This is the LED.
Thanks!
Unfortunately, I made a royal mistake. I tried wiring the MOSFET on my own before looking at/understanding your schematic and fried my laptop. My power supply was reading 8 VDC and knowing the LED requires more I cranked it up to 15 and noticed smoke coming from the Arduino. I figured I destroyed the Arduino but then realized my laptop had turned off. Obviously I wired something incorrectly.
Looks like this project is on hold until I can figure out if my laptop is repairable. Thanks for your help thus far.
Revisiting this topic after many months. The light I linked above is PNP only - may I ask why your diagram has callouts for two lights (one PNP and one NPN)? The entire project only has one light which is OFF in all states unless a JAM is detected and then it turns on. Thank you.
Both were shown in the schematic to demonstrate the two different options you can have.
