IR sensor (emitter and phototransistor) dysfunctional

Projects General Guidance
1

We've been stuck on this issue for a while now. Basically, we have an IR base pair -- an emitter and a phototransistor -- that is supposed to detect motion. Here is the code.

void setup() {
  Serial.begin(9600);
   pinMode(A3, INPUT);

  pinMode(2, INPUT);

}

void loop() {
  int sensorValue = analogRead(A3); // change A0 to your sensor pin
  Serial.println(sensorValue);
  delay(500);
}

However, everytime we run the code and make changes, numbers on the console display as either only 0 or 1 (from digital) or 1023 (from analog), and are not actually responsive to motion close to the sensor.

20250602_095129
20250602_0951291920×1080 266 KB

We know that the LED emitter is working as we have used our smartphone cameras to detect the infrared light successfully.

Any help is greatly appreciated.

2

This setup is not supposed to give you the distance. If you want to measure the distance of the nearest obstacle, you have to use a SONAR sensor.

1 Like
3

Thank you so much for your clarification. We meant motion sensing by infrared radiation, sorry.

4

It is more helpful to take a picture of a hand drawn wiring diagram carefully labelled. The picture you posted is incomplete and probably misleading.
BTW, who is 'we'

5

IMG_4020
IMG_40201920×1243 157 KB

1 Like
6

That looks like a kit you wired up. what kit? As @LarryD pointed out, your resistor has both ends in the same row of holes (e.g. tied together) so isn't doing anything. Most definitely wired wrong.