Hall Sensor does not work :(

V is connected to the 5V Pin, GND is connected to the GND Pin and the last Pin is connected to Pin 2.
This is my test sketch but there is no change when there is a magnet infront of the sensor.
Sensor is a TLE4905 I think. Arduino Nano V3.

int readpin = 2;  
int incoming = 0;
void setup ()
{
  pinMode (readpin, INPUT) ;
  digitalWrite(readpin, HIGH); 
  
  Serial.begin(9600);
}
void loop ()
{
  incoming = analogRead(readpin) ;
  Serial.println(incoming);
  delay(80);
}
int readpin = 2;

To which pin is the sensor connected? Digital pin 2 or A2 (analog input)?

The sensor is a switch so could be connected to digital pin 2 (with internal pullup enabled*) and read with digitalRead(2). If you use analogRead(2), pin A2 will be read.

The sensor is sensitive to one magnetic pole. See page 4 of the data sheet.

What Arduino board are you using?

Read the how to use this forum-please read sticky for some advice on how to get the most from the forum.

The sensor is open collector NPN so a pullup resistor is required.

Its the digital pin 2.

digitalRead(2) just gives me "1", no matter if there is a magnet or not.

Tried both poles.

digitalRead(2) just gives me "1", no matter if there is a magnet or not.

That means that it is not switching. The pin will go low when it switches.

Page 2 of the data sheet shows the pin out. I would suggest that you double check that you have it wired correctly.

" sensor is a switch so could be connected to digital pin 2 (with internal pullup enabled*) "

"The sensor is open collector NPN so a pullup resistor is required."

So do I need an external pullup resistor or can I use the internal one?

"Page 2 of the data sheet shows the pin out. I would suggest that you double check that you have it wired correctly."

The labeled side of the sensor faces towards me and the left pin is connected to the 5V pin, the second pin is connected to the GND pin and the last pin is connected to the D02 pin

You could try 10K or 4.7K but the internal pull should be enough pullup.

I don't know what else to try.

Maybe post a photo showing the wiring?

I don't know why you would expect to be able to READ digital pin 2 with a digitalWrite command. Does that make any sense ? It can only be READ with a digitalRead() command.

There should be a pullup resistor (4.7k) on Q and it should pull the output to LOW near a magnet.

Did you put a meter on the output and measure the voltage when it should be ON ?

What value is the analog pin returning when a magnet is near ?

  pinMode (readpin, INPUT) ;
  digitalWrite(readpin, HIGH);

raschemmel, that is the old way to enable the internal pullup*.

I wired a similar hall sensor to my Uno and tested the code below. The code works. Try the magnet in all orientations. The poles may not be how you expect.

const byte sensorPin = 2;
boolean sensorState;

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

void loop()
{
  static unsigned long timer = 0;
  unsigned long interval = 500;
  if(millis() - timer >= interval)
  {
   sensorState = digitalRead(sensorPin);
   Serial.println(sensorState);
  }
}
Prior to Arduino 1.0.1, it was possible to configure the internal pull-ups in the following manner:

pinMode(pin, INPUT);           // set pin to input
digitalWrite(pin, HIGH);       // turn on pullup resistors

Ok, so the Arduino is connected to a battery-pack (GND Pin to "-" and Vin Pin to "+" I think).

But while I programm the Arduino, it is powered over USB.

If I turn on the battery-pack, the hall-sensor works but it does not work just over the usb connection. But the LED-strips that are also connected to the Vin and GND pin are working without usb (but they are less bright).

While testing the hall-sensor, the LED's are not in use.

Ok, so the Arduino is connected to a battery-pack (GND Pin to "-" and Vin Pin to "+" I think).

But while I programm the Arduino, it is powered over USB.

If I turn on the battery-pack, the hall-sensor works but it does not work just over the usb connection. But the LED-strips that are also connected to the Vin and GND pin are working without usb (but they are less bright).

While testing the hall-sensor, the LED's are not in use.

None of this is relevant. Stick to the questions:

  1. What is the analog pin returning near a magnet ?
  2. Did you measure the voltage on the Q pin ? (with and without a magnet)

If I turn on the battery-pack, the hall-sensor works but it does not work just over the usb connection

What is supposed to be the significance of this statement ? What is it supposed to mean

Why are you talking about LEDs ?

This post is about a hall sensor.

"None of this is relevant. Stick to the questions:"

Why is this not relevant if it works with an external battery-pack while it does not work over usb? I'm talking about the LED's to show, that they can get power from the Arduino while the Arduino gets its power over the usb connection to the pc. Sorry, maybe its my english that is to bad so you dont understand what I mean...

This should suggest to you that the USB is not supplying enough power but without a schematic of your circuit so it hard to troubleshoot your problem , other than to say this post shouldn't be abouit a hall sensor since there is obviously nothing wrong with it. It cannot be good one second and bad the next. You need to forget the hall sensor and focus on your power wiring and what is different when running off the battery. Since you have yet to post any voltages, I don't see how we can be of help with no information.

I just found it out after I have created this thread. So yeah, now we know that the Hall-Sensor is working and the problem is the power wiring. And since it does work with the battery-pack the problem is somehow solved.

Thanks for your help!

I just found it out after if have created this thread. So yeah, now we know that the Hall-Sensor is working and the problem is the power wiring. And since it does work with the battery-pack the problem is somehow solved.

I have seen no evidence that there ever was a problem. (with the hall sensor)

raschemmel: I have seen no evidence that there ever was a problem. (with the hall sensor)

Dude, what is your problem? I just THOUGHT that the problem was the hall-sensor or something related to the hall-sensor. Now I know that the problem was NOT the hall-sensor.

THE PROBLEM WAS NOT THE HALL-SENSOR THE HALL-SENSOR IS WORKING PERFECTLY FINE THE HALL-SENSOR IS GREAT HAVE A NICE DAY

Thank you for setting the record straight. My last post was simply a response to the your comment ;

the problem is somehow solved.

, since if there never was a problem, it could not have been 'somehow solved'. I don't know why you are so sensitive to facts. This is the forum. Other posters read these posts. It is counter productive to have posters post for a problem and end there post by saying : "the problem was somehow solved." What are other newbies supposed to think when they read that ? If it makes you uncomfortable to admit there was no problem that's too bad. You have a responsibility to set the record straight at the end of the post, which you finally did after some prodding, but honestly I fail to see how you can be angered by me wanting to set the record straight for the sake of others, who can now relax, knowing that the code you posted is in fact good code. Instead of overreacting, you should have simply replied:

"Yes, that is correct, there never was a problem." (with tha hall sensor), and left it at that.

FYI - many people read the forum to learn and seeing problems that others have can save a lot of frustration. When I first started I went through the forum to see what problems others have had - seems to me I worked back about two years of posts - found several small tidbits that were not in most books but very valuable for a reliable project or cute tricks I could use to make a project better or simpler

so what ever your problem was and the solution could be useful to others. That is why the push here for a schematic as well as the solution