Reading out NPN (NO) sensor using Arduino Nano

Projects General Guidance
1

Currently I'm trying to read out this sensor as part of a bigger project (see the bottom of this post for those who are interested).

Eventhough the sensor works (it has a build-in LED) I can't seem to get a reliable output.

My circuit looks like this, the power supply is 24V:
circuit

and my code:

void setup() {
  Serial.begin(9600);
  pinMode(4,INPUT_PULLUP);
}

void loop() {
  Serial.println(digitalRead(4));
  delay(500);
}

Does anyone see what I'm doing wrong?

Project information:
I want to use a proximity sensor that turns on a LED-strip when someone enters my driveway when the sun is down. Currently I'm testing with an Arduino nano but will switch to a NodeMCU V3 so I can easily integrate it into my HomeAssistant setup. A NodeMCU will also easily allow me to do API calls to get the sunrise and sunset (I think, haven't looked into it yet tbh).

I know this might not be the easiest/most logical setup, but it seemed fun to do it this way with all the different types of challenges

2

Sensor is connected to 4 and you are reading 2

1 Like
3

Sorry, you're right that was a WIP error, which I forgot to change when I switched pins. :zipper_mouth_face:

Updated the post, since unfortunately it wasn't the solution.

Thanks for the quick response though!

4

You changed the pin in your code. That's bad. Now @jim-p's comment looks crazy. But I saw it before you changed it and so can anyone else by using the "view changes" pencil icon.

5

I did reply to @jim-p, but I think your comment beat me to it

6

The way you connected it should work.

Post a link to the datasheet for the sensor.

Yes, I have some code I can share if you want.

1 Like
7

I tried to look for a datasheet as well, but all I have is the alieexpress page. I guess that will teach me for buying cheap chinese sensors. :zipper_mouth_face:

9

You could try adding a 4.7K pull-up resistor between DATA and nano 5V output

10

I think you got an absolute bargain there! Just £5.83 and you never need to wash your car again!

Screenshot_20240624-163157-585
Screenshot_20240624-163157-585934×420 16.4 KB

I think it is pretty smart!

11

Tried that as well, but to no avail. I'm starting to think it might be the sensor, since it also occasionally shows weird behaviour on the build-in LED.

12

Yeah :joy:.... starting to think that spending a little more would have been wiser.

Do you have any recommendations for sites/sensors like this?

I basically need a breakbeam (because I dont want it to be triggered by a passerby) sensor for ~7m

13

It's not actually a proximity sensor. I think it's a beam-break sensor. You need something to bounce the IR light back to the device.

EDIT: ah, you realise it's a beam-break sensor :slight_smile:

14

That's the other thing, I did get a (what they call) feedback reflex.

However, when it's in 'line-of-sight' of the sensor it just turns off the LED and nothing turns it on again.

15

The beam need to be blocked for it to work. If you use something reflective to block the beam you will probably still get a response. If it says 7M so the lenses are probably set up for that distance only.

16

Do you think that means each-way or the return trip?

17

It's a reflector similar to those on the rear of your car (assuming you have them in your country (reflectors, not cars, I mean)). The reflector's surface consists of a matrix of small corner-reflectors that bounce light back in the direction it came from.

Other shiny surfaces will reflect the light off at some angle, and miss the sensor, unless you align them very carefully.

18

@PaulRB @jim-p Testing some things rn, using a bigger distance and the reflector. The behaviour seems more consistent. Will keep you posted, but it can take a while (hard to test things this way)

19

It does have a distance adjustment.
You will need to play around a bit

20

The code you posted in the original post prints the output of the sensor on the serial output. Then you have a 500ms delay before you print again.
The sensor output could change, and then change back again during that 500ms and your code wouldn't detect it.

Have a look at the IDE Example 'StateChangeDetection' to see how you can Serial.print() only when the sensor output changes.

21

Power supply to what exactly?