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Hall-effect sensors are used to detect magnetic fields. Traditionally, before the addition of silicon into the sensor, they were difficult to interface into a custom circuit. Often these non-silicon Hall-effect sensors would draw too much power, were too large, or were too complicated for today’s designs.

However, Texas Instruments’ (TI’s) line of DRV5000 silicon based Hall-sensors are tiny, low power, and comparatively easy to interface with only 3 pins. This product line is intended to be a low cost alternative that may also save power and space in your design.

Hall Sensor Benefits

Hall sensors are by no means a new technology. They were invented in 1879 by Edwin Hall and use his “Hall Effect” to detect magnetic fields through changes in the electric field. This means that compared to other magnetic sensors (like reed switches), Hall-effect have no contacts and will not experience wear and tear. They are also not susceptible to noise, RF signals, air or dust so they lend themselves to a wide range of applications.

Hall sensors are typically used to determine an object’s acceleration, speed, or position. However, they can also be used for index counting and object recognition. This means they are well suited for use in electric motors, flow meters, proximity alarms, valves/solenoid and tachometers among many other applications.

The DVR 5000 Series

TI’s DRV5000 line of Hall-effect sensors were designed with ease of use and circuit compatibility in mind. This can be seen in the line’s features, including:

• A wide voltage range: 2.5v – 38v
• 3 pin small package: SOT-23 2.92 mm x 2.37 mm or TO-92S 4.00 mm x 3.15 mm
• Excellent sensitivity over a wide range of temperatures: -40 to 125°C
• Reverse supply protection up to -22v
• Output short-circuit protection
• Output current limitation

For detailed features of each product in the DRV5000 line, TI’s products page can simplify your selection. And at a price of $0.26 |at 1 ku they are highly competitive in price.

Start by looking at the DRV5013 Digital-Latch Hall Effect Sensor.  This is a bipolar sensor that can sink up to 30mA.  It has a fast power on time of 35µs and a fast response time. This chip is usually used as a sensor for brushless DC motors . Here the DRV5013 is being used in two designs; PWM control of a motor and closed-loop speed control which provides precise RPM.

If you have a need for a digital switch then the DRV5023 might be right for your design. It is a Digital Unipolar-Switch Hall Effect Sensor with similar features to the DRV5013. Thanks to the digital switch and low power draw, this system, and the rest of the DVR5000 family, can be used to create an intelligent Hall-sensing system that runs on a coin battery. Additionally, its “normal mode” can be set to fluctuate between sampling and “standby mode” allowing a power usage less than a micro amp and a service life of over 20 years. The DRV5023 could be used for docking station detection, door open/closed detection and pulse counting.

How it Works

Figure 1 shows that the output is normally high and is pulled low when the south pole of a magnet is perpendicular to the marking on the chip; this is the operate point (B _OP ).  Additionally, when the north pole of a magnet is near perpendicular to the marking the output will release or unlatch; this is the release point, (B _RP ). In between B _OP and B _RP hysteresis is included indicated at the output by a High-Z state.

Figure 1 - Bipolar Digital Latch OUT

Figure 2 shows that when the south pole of a magnet is perpendicular to the marking with field strength greater than B _OP then the output is pulled low.  The output will release once the field strength drops below B _RP .

Figure 2 - Unipolar Digital Switch OUT

If your switch needs to activate on either pole of the magnet, then the DRV5033 is what you need.  It is a Digital-Ominpolar-Switch Hall Effect Sensor.  Figure 3 shows that if field strength above B _OP is detected from either pole of a magnet the output is pulled low.  It will be released when the field strength drops below B _RP for either pole.  Hysteresis is included between B _RP and B _OP for both poles, indicated by a High-Z state on the output, preventing false triggering.

Figure 3 - Ominpolar Digital Switch OUT

If your design needs to detect which magnetic pole is near the sensor, then the DRV5053 is the likely best fit.  You can see in Figure 4 that the output produced scales with magnetic field present.  When the south pole of a magnet is detected the output will drop below 1v and when the north pole is detected the output goes above 1v.  The amount above/below is dependent on the field strength of the magnet, indicating how close or far away the magnet is located.

Figure 4 - Bipolar Analog OUT

The DRV5053 will work well in flow meters, for docking adjustments, vibration correction and damper controls.

Prepackaged Kits and EVMs for Motors

TI uses their Hall-effect sensors in their motor control technology. This packaging will help to speed up your design time and effort when connecting the sensor to a motor.  In addition, TI offers other motor control technology, such as InstaSPIN™ – FOC (Field-oriented control) and InstaSPIN™ – Motion kits and evaluation modules, are available for:

• Stepper motors
• Brushed DC motors
• Brushless DC motors
• Permanent magnet synchronous motors
• AC induction motors
• Microcontrollers for precision control

Conclusion

TI has a strong line of Hall-effect sensors that may change how you design switching, latching and analog control circuits.  Using magnetic and electric fields, there is no contact required. This will increase the time to failure, and make dust or RF interference meaningless.  Plus, using TIs available development tools makes design quick and easy.

Texas Instruments has sponsored promotion of their Hall Effect Sensors on ENGINEERING.com. They have no editorial input to this post - all opinions are mine.  Christine Halsey