Hi everyone,

There are boards with IR sensors on the market that looks like this: the IR.PNG picture


I have all the components to build one myself with the Arduino Uno, VCNT2020 sensor and LM393. The schematic is the example.jpg picture (it's the schematic of the sensors on the market)
The picture LM393.png shows what pins I connected to the LM393.

The problem is that in the serial monitor, the display message is ''STOP'' but nothing else is in front of the sensor.
Even if I rotate the potentiometer, nothing changes.


I disassembled and reassembled everything a couple of times because I thought that I didn't connect something but it led to the same result.


Any help will be much appreciated

This is the code I used, it's from this website https://www.elithecomputerguy.com/2019/06/ir-sensor-digital-output-on-arduino/
#define IR 8

int Obstacle;

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

void loop() {
Obstacle = digitalRead(IR);

if (Obstacle == LOW) {
Serial.println("STOP");
}
else {
Serial.println("All Clear");

}
delay(500);
}

 

Did you install pull-up resistors on the output of the comparator?

 

Did you install pull-up resistors on the output of the comparator?

Yes I did. The 10k one which is in parallel with the 1k

 

Pin 6 should be connected to ground. And pin 5 should be connected to pin 7. The input pins are floating and may be responding to ghost inputs, affecting the operation of the comparator in use.

 

Does the LED switch on and off when testing the sensor ?

 

The IR circuit is very crude .
Stray IR will affect the performance causing false triggering.
Is the output of the op amp high or low when nothing is in front of the transmitter and detector.

 

Does the LED switch on and off when testing the sensor ?

it's on all the time

The IR circuit is very crude .
Stray IR will affect the performance causing false triggering.
Is the output of the op amp high or low when nothing is in front of the transmitter and detector.

it's high all the time

 

If the LED is on all of the time the output from the LM393 is low.

 

If the LED is on all of the time the output from the LM393 is low.

Does this mean that something is wrong with the LM393?

 

Does this mean that something is wrong with the LM393?

Probably not. Most likely the IR sensor is activated continuously. Do you have a voltmeter to test with?

 

Hello,

The sensor is quite different to the one in the picture in the first post.


What is the used supply voltage?
The sensitivity of the sensor may be to high:


Bertus

 

Actually you can test the circuit by removing the connection on the sensor connected to the 10K resistor.
Set VR1 in about the middle. If the circuit is good the LED should be OFF.
If you short that connection to ground the LED will always be ON.

 

Pin 6 should be connected to ground. And pin 5 should be connected to pin 7. The input pins are floating and may be responding to ghost inputs, affecting the operation of the comparator in use.

did that, no change

 

did that, no change

Too bad it didn’t help. But you should keep it. Unused op amps should always be connected in some way. Search for “unused op amps” for more detail.

 

Probably not. Most likely the IR sensor is activated continuously. Do you have a voltmeter to test with?

I tested the LM393 and potentiometer. Both work just right

 

I tested the LM393 and potentiometer. Both work just right

What about the Optoisolator? Does the non-inverting input to the LM393 change when you cover the “tube” shown in your drawings?

 

UPDATE

After some wiring check and I ditched the 104 capacitor. The circuit kind of works.
When I rotate the potentiometer, at some point it says "STOP" even though nothing is in front and when I rotate back it says "All Clear"

In another test, I rotated the potentiometer until it says "All Clear", I placed a white paper in front of the sensor and rotated the potentiometer until it said "STOP". After that, I took the paper out but the message didn't change to "All Clear"

I did the same test with a different sensor, the ITR20001/T but now apparently I can change the value only by rotating the potentiometer but the sensors are not affecting anything

 

FINAL UPDATE

I made it work!
Basically, I just removed the potentiometer and connected the pin 2 to the ground and now it works without a problem

Thank you guys so much!!!!!!!!!!!!!!!!!!!!!

 

if (Obstacle == LOW) {

I don't see where 'LOW' is defined...

 

I don't see where 'LOW' is defined...

It’s a reserved word in the Arduino