# Hall Effect sensor to monitor home electrical apparatus

1. Dec 19, 2011

### florenceooi

Hi Guys,

I'm currently doing my final year project which my title is to design a remote sensor to monitor home electrical apparatus by using hall effect sensor.

I've build a basic circuit and amplifier to test my hall effect sensor ic ( linear) with a magnet. Everything works fine and now I'm going to use the hall effect sensor to detect the current flowing through a conductor. It seems like the hall effect sensor cannot detect the magnetic field generated when current flowing through the conductor.

1) can the hall effect sensor IC actually detect the magnetic field generated by a conductor if i place it near to the conductor?

2) or shall I build a hall effect current tranducer in order to detect the magnetic field?

Your help would be much appreciated.

Thanks.

2. Dec 20, 2011

### MATLABdude

Welcome to PhysicsForums!

Which Hall Effect sensor did you use for your project, and what was your methodology for determining that "Everything works fine"? This presumes you bought a pre-made one rather than attempting to build your own.

EDIT: I should probably also ask how much current you're trying to measure.

3. Dec 20, 2011

### jim hardy

and remember if you're trying to measure using the power cord,,,,,,,,

current goes one way in one conductor and opposite way in other
so a few wire diameters away from power cord net magnetic field is zero. the opposing currents cancel out......
Gauss' law: closed loop integral of h dot dl = i-enclosed, which if you enclose both wires is zero.

separate them and try again.

4. Dec 20, 2011

### florenceooi

Hi, sorry for not make my statement clearer. The hall effect sensor that I'm using is hall effect switch AH182. I said everything works fine as in testing the hall sensor. I build a simple circuit with LED to test the hall effect sensor. When the magnet ( south pole ) is close to the sensor, the output of the sensor increase, and the LED is light up. When i moved away the magnet the LED is light off. When the magnet ( north pole ) is close to the sensor, the output of sensor decreases and the LED is not light up.

Now, i have to test my sensor with the home electrical apparatus. Let's take electric kettle as an example. I place the hall effect sensor near the power supply conductor, but no changes at the sensor's output, it seems like the sensor cannot detect the magnetic field produced when the current flowing through conductor? My home power supply is 240V.

5. Dec 20, 2011

### vk6kro

Your electric kettle will be using AC current so the output of the Hall Probe (if you put it near only one of the input wires to the kettle) will be AC too.

So, you probably won't see this on your LED display.

Did you read this in a post above:
Jim Hardy
current goes one way in one conductor and opposite way in other
so a few wire diameters away from power cord net magnetic field is zero. the opposing currents cancel out......
Gauss' law: closed loop integral of h dot dl = i-enclosed, which if you enclose both wires is zero.

6. Dec 20, 2011

### Carl Pugh

The Ah182 doesn't appear to be a linear hall effect sensor.
One method to obtain information on hall effect sensors is to go to either Digi-Key or Mouser Web sites and search for hall effect current sensors. Then pick out a sensor and click the button for data sheet.
Another approach would be to Google "Hall effect linear current sensor".

7. Dec 20, 2011

### vk6kro

Yes, you are right. It is a Hall switch.

I've started using Web Ferret which is free and it searches a lot of search engines at once.

8. Dec 22, 2011

### Dmytry

Hall switch activates when magnetic field exceeds particular value. If the magnetic field from the wire doesn't exceed that value then the switch won't activate. Furthermore typical power cord has two wires with opposite currents, whose magnetic field nearly cancels out.
Hall effect sensors are not very sensitive magnetometers.

By the way, you can feel current in wires if you hold a small neodymium magnet in your fingertips, near the wire. Even when its just a hundred watts.

For AC current you can use a coil and detect alternating magnetic field.

9. Dec 22, 2011

### florenceooi

Thanks for all the advises,guys! I will try to do again and post my outcomes. Thanks =)

10. Dec 23, 2011

### Mike_In_Plano

It's good to remember that Hall effect sensors measure magnetic flux density. The flux circulating around a single conductor drops off very quickly as the sensor is moved away. Likewise, if you have two conductors, one carrying current to and the other away from the load, then the field from one will cancel the field from another.
Hall based ammeters use a magnetic core with a slot where the Hall fits. The conductor passes through the core to induce an improved (and more predictable) flux density.
Higher performance ammeters have windings on the core that are driven by the amplified output of the Hall sensor such that the net flux is held to near zero. By monitoring the driving current, a very accurate measure of the current can be made displite variations in the core construction or Hall properties.