Two Hall Effect Inputs Using One Pin

Hi there,

Question regarding the potential hookup of two A3144 digital hall effect sensors to a single Arduino digital input pin.

My idea is that I can couple the outputs of the sensors to the same input pin since I do not need to differentiate the two inputs, however I am uncertain if this could cause damage to the sensors or the Arduino. Any input on this would be appreciated. Apologies that my linked schematic's sensors are incorrect, Fritzing did not appear to have a basic A3144 so I had to improvise.

I have not worked with hall effect sensors much and could not find any resources to help me regarding this issue, so I came here. Thanks in advance :slight_smile:

Your diagram has the input pin tied HIGH. The A3144 outputs go to the Arduino input, the resistor goes from the input to Vcc (optional if internal pullup enabled).

Since the A3144 Hall effect sensors are open collector (drain) you can connect the outputs together. You need 1 pullup resistor from the A3144 outputs to Vcc. The internal pullups on the pin will often suffice unless wires are long. Then a lower value (10K or less) will be required.

Test code (tested and works):

const byte hallPin = 8;

void setup()
   pinMode(hallPin, INPUT_PULLUP);

void loop()

Pin goes LOW in mag field.

Why not posting a link to the datasheet? That would impress on helpers and contribute to interest and replies.

There's more that usually lacks in toy Fritzings...
That rigging is not working, no power supplied... (Poor powering is a usual reason for issues here.)

That sensor needs a pullup resistor. Use 4,7k down to 270 Ohm.
Then You can wire both sensor outputs together.

Thank you so much for the reply. The schematic is especially helpful in guiding my wiring for this circuit. I'll be able to get back to work on this project in the morning. :slight_smile:

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For future efforts, you can also read about ‘diode-or’ circuits. Which can offer an option if the output is ‘driven’ i.e. the output isn’t open_collector

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