![3-pin Hall Effect switch](hall/hall2a.webp)
Using Ratiometric Hall Effect Sensors
A ratiometric Hall effect sensor outputs an analog voltage proportional to the magnetic field intensity. The devices I will use here are the UGN3503 and the Texas Instruments TL173C.
Both are unipolar devices one operating at 5-volts and the other at 12-volts respectively. With no magnetic field applied the output is about one-half the supply voltage.
The voltage will increase with the south magnetic pole on the face or decrease with the north magnetic pole on the face.
- YouTube videos:
- Basic Hall Effect Sensors YouTube
- Hall Effect Sensor Circuits YouTube
- Basics of Hall Effect Analog Sensors & Switches Pt. 1
- Operate, Build Hall Effect Switch Pt. 2
- Hall Effect Latches Theory and Circuits Pt. 3
The ratiometric Hall effect sensor is demonstrated in the latter third of the above video.
Spec sheets in PDF: TL173C and UGN3503.
Pictured above are typical pin outs on three lead Hall sensors. A ratiometric instead of switching on or off outputs a voltage from near zero to almost VCC proportional to the strength of the magnetic field and magnetic polarity.
Considering Magnets
The magnetic field typically produced by rare-earth magnets can be in excess of 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla. The Tesla is named in honor of the inventor, physicist, and electrical engineer Nikolai Tesla. A smaller magnetic field unit is the Gauss (1 Tesla = 10,000 Gauss):
10-9 - 10-8 gauss: the human brain magnetic field;
0.31-0.58 gauss: the Earth's magnetic field on its surface;
25 gauss: the Earth's magnetic field in its core;
50 gauss: a typical refrigerator magnet;
100 gauss: a small iron magnet;
2000 gauss: a small neodymium-iron-boron (NIB) magnet;
15,000-30,000 gauss: a medical magnetic resonance imaging electromagnet.
Above ref. Wiki. To find out more about rare earth magnets in general visit www.rare-earth-magnets.com. Magnets can be stacked (N to S) to form a more powerful magnet.
Let's consider the specifications for a Texas Instruments TL173C Hall sensor. At zero gauss the output is 6 volts. At 50 mT (1/1000th Tesla = 10 gauss or 500 gauss total) the output voltage is 7 volts. That is on the south pole of the magnet. At 50 mT. (500 gauss) the output voltage is 5 volts with the north pole.
Note that magnetic flux flows from north to south in conventional theory. Positive donates south, negative donates north. So -50 mT is -500 gauss north polarity.
We can also use electromagnets.
![Ratiometric Hall effect sensor](hall/hall3.webp)
We can use the above circuit to read the output from the sensor. The voltage reading will give us an idea of the polarity and strength of a magnet. This opens the door to a number of interesting uses for these sensors. Let's look at a few.
![Hall effect measure current](hall/ex10.webp)
Calibrated linear Hall device in this example will measure the current through the wire. The higher the current the stronger the magnetic field and thus a higher output voltage.
![Hall effect sensor and LM311 and differential amplifier.](hall/hall8b.webp)
Using a Comparator
Pictured above we have connected the sensor to a LM358 used as a difference amplifier feeding a LM311 comparator. We can adjust the potentiometers to set a trip point on the output . Unlike a standard Hall effect switch we can vary the sensitivity. The LM311 has an open collector output and can drive any number of small relays, opto-couplers, etc.
While this is a 12-volt circuit note the pull up resistor connected at TP4 connected to 5-volts.
Also see Voltage Comparator Information And Circuits
![Hall effect sensor and LM311](hall/hall8.webp)
The circuit will also work at 5 volts as is, but use the UGN3503 or other 5-volt sensor instead. In the case of the UGN3503, disconnect it from the 5-volts and use 6 volts for greater sensitivity if desired.
![Hall effect sensor internal diagram](hall/hall2b.webp)
Inside a typical three-pin ratiometric Hall sensor.
- Hall Sensor with Alternating Current
- Using Hall Effect Switches and Sensors
- Using Ratiometric Hall Effect Sensors
- Hall Effect Sensors with the Arduino
- Quick navigation of this website:
- Basic Electronics Learning and Projects
- Basic Solid State Component Projects
- Arduino Microcontroller Projects
- Raspberry Pi Electronics, Programming
- Spec. sheets all PDF formate:
- UGN3013 Hall Switch (PDF file)
- TL173C 12-Volt Ratiometric Hall Sensor
- UGN3503 5-Volt Ratiometric Hall Effect Sensor
- Honeywell SS466 Hall Latch
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