I need a better Hall Effect

Other Hardware General Electronics
1

Hi, I am using some 3144 sensors and they seem to latch on.
The magnet gets quite close, 1/16" and it turns on, then stays on until the magnet has passed out to about 1/2". It seems like one side is more sensitive than the other.

This would be OK for a door or something like that, but I am trying to measure wind-speed and the magnet is coming around fast. Is there a better Hall sensor I can use?

I tried moving the magnet back, but it does not help. It has to be close enough to turn it on, then it stays on until the magnet is well away from it.

I was using a 10K pull-up resistor but decided to test with the pinMode approach and it works the same.

const int hallPin = 6;

void setup() {
  Serial.begin(115200);
  pinMode(hallPin, INPUT_PULLUP);   
  Serial.println("Ready");  
}

void loop(){
  if (digitalRead(hallPin) == LOW) {     
    Serial.println("ON");
  }
}
2

Try a weaker magnet, preferably a long bar type.

3

The A3143 looks better suited to your purposes with less ratio between on operate and release
flux densities. Its obsolete as is the A3144, but the replacement device for the A3143 is the A1103

4

@SalineSolution
May I ask if you thought about using a reed switch instead of hall sensor? I plan to build a wind sensors, too. But I thought a reed switch is easier to use and operate.

Best

5

It sounds to me like the orientation of your sensor is wrong. Try rotating it.

6

Reed switches wear out, hall sensors don't...
Probably an important consideration for a wind speed sensor.

7

@SalineSolution
Have you thought about adding a second magnet with inverted polarity a few mm behind the first one to force the hall sensor to change?

MarkT:
Reed switches wear out, hall sensors don't...
Probably an important consideration for a wind speed sensor.

Interesting. I thought the life expectancy of about 10^8 operations would be good enough for some years.
Btw. hall effect sensors and ICs in general, respectively, do not wear off over time? I thought all electronics does suffer over time?

Thanks & best

8

I don't see ion-migration or thermal cycling being issues with a hall-sensor, its not a high stress
component. Last for centuries probably.

9

MarkT:
Reed switches wear out, hall sensors don't...
Probably an important consideration for a wind speed sensor.

Mark, you have that correct. I am rebuilding a combined commercial unit (2010 on the main PCB inside) and it has reed switches for the wind-speed and rain. One is dead the other intermittent so decided on Hall.

More importantly, when I get to the wind direction I intend to use 8-Hall spaced around the disk and a single magnet. But the spacing will be less than the Hall/magnet "let-go" distance I have discovered with the wind speed.

The mechanicals of the unit are all OK, so the reversed follow-up magnet is worth trying.

10

aarg:
It sounds to me like the orientation of your sensor is wrong. Try rotating it.

The 3144 seems t work one side for the North-Pole and the other for the South-Pole. Not sure which is which with the little bar magnet I have.

The flat side of the 3144, (no markings) works as mentioned with one end of the magnet and I get nothing with the other end. If I swap sides of the 3144 ("3144 0880") the other end of the magnet works as mentioned.

Either way it still has the lag.

11

If you used linear Hall effect devices for your direction indicator, you could interpolate to get a more accurate reading. Particularly if you calibrated for the angle.

Allan