Hall Effect Sensor Wiring

[ppuxley]

I have an automotive 3 wire Hall Effect Sensor for a speedo from a Ford Falcon-I want to use it in a kit car speedo application, but I am unable to identify the function of each of the wires.
Is there a simple test I can do to identify which is Ground, 12v power and signal . I am concious that I cant just experiment with 12v , as I run the risk of blowing it.
Hoping someone can help

Patrick

 

[Grossel]

I have found two pictures illustrating the pinout from two types of hall censors. As you see, none of them use 12V as input voltage.

 

[ppuxley]

Grossel
Thanks .
It being an automotive application I know that this is powered by 12v. Maybe there is something in the unit that moderates the voltage applied to less than this.
But what I need to ascertain is the function of each lead without blowing the device.
Vin
Ground
Signal

If I start playing around with it and apply any significant voltage to the signal lead , I risk burning it out, dont I?

Patrick

 

[justDIY]

I have an automotive 3 wire Hall Effect Sensor for a speedo from a Ford Falcon-I want to use it in a kit car speedo application, but I am unable to identify the function of each of the wires.
Is there a simple test I can do to identify which is Ground, 12v power and signal . I am concious that I cant just experiment with 12v , as I run the risk of blowing it.
Hoping someone can help

Patrick

visit your library and look at the repair manual for that model year (or similar) car, it will have the wiring information you seek.

alternately, the output should be high impedance to the power pins, so you could try measuring the resistance the pins all have to each other. if your multimeter has a diode test function that might be useful.

once you've got a guess as to what's what, connect everything through a 4.7k to 10k resistor, that will limit the current in case you guess wrong and prevent magic smoke from escaping.

 

[ppuxley]

justDIY
Thanks. I trawled the internet and found a manual for a Falcon ,hoping to find a wiring diagram, but surprisingly there wasnt one that showed the Speedo Sensor .
Will try your resistor method.
Can you explain in what way I would use the diode test function
Thanks
Patrick

 

[Mr RB]

All the pins will be safe at 20mA. Use a 1k resistor in series with the 12v line. Connect power to 2 pins ie 12v and gnd and test.

The output pin is almost always open-drain ie it will only pull down, it won't source voltage. So connect the output pin with another 1k series resistor to 12v.

They are pretty sturdy sensors, at 20mA they will take continuous reverse connectoin etc so do worry too much, use the resistors and test every combination until you got it working.

 

[ppuxley]

Thanks, Mr RB, will have a crack at it this weekend