WEBVTT
Kind: captions
Language: en

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♪♪

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Hello.

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Today we're demonstrating NVE's ABT-Series,  

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a new line of tunneling magnetoresistance 
gear tooth sensors. We'll achieve resolution  

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down to a few thousandths of a degree of 
a rotation with these precise new sensors.

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ABT-Series gear-tooth sensors are manufactured 
with NVE's state-of-the-art TMR technology,  

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which has fundamental sensitivity advantages over 
Hall-effect, AMR, and even our own legacy GMR  

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products. ABT sensors are dual-channel sensors 
consisting of two passive Wheatstone bridges.

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They are typically used in conjunction with 
small ceramic magnets in a back-biasing  

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configuration, most easily achieved by 
placing the magnet behind the sensor  

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on the reverse side of a printed circuit board. 
The magnet generates a source of magnetic field,  

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which enables the sensor to detect 
gradients from passing metal objects.

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ABT-Series sensors detect only the horizontal 
component of magnetic field in the plane  

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of the sensor package, so they need to be 
pitch-matched to the target gear for optimal  

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performance. Standard ABT-Series products 
cover a wide range, from tiny pitch gears  

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found in miniature robotics up to larger 
gears found in automotive applications.

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Here's the demo board. We're using an 
ABT375-00E sensor to detect  

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a 30-tooth, 0.5-module carbon steel gear. 
The ABT375 sensor is  

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back-biased with a small ceramic magnet,  

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following the recommendation 
in the product datasheet.  

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The sensor outputs run to two 
separate signal processing circuits.  

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The first circuit amplifies the sensor 
outputs before feeding into the ADC channels  

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of an inexpensive ATTINY85 microcontroller. 
The microcontroller calculates  

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the angle and displays the result 
on an eight-digit display.  

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Since this is an incremental encoder,   

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we also added a zero button to set 
the zero angle when the circuit is powered.

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The second circuit uses a comparator to 
generate digital A and B pulses directly from  

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the unamplified sensor outputs. The A and B pulses 
are about 90 degrees apart, since we matched the  

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pitch of the sensor to the gear according to the 
datasheet. Therefore we can use a simple flip-flop  

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to generate a direction indicator, in addition 
to the tooth detection the A or B pulse gives us.  

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We'll turn on the power.  

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The angle is displayed in degrees 
with three decimal places of resolution.  

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As we turn the gear, the LEDs indicate the 
direction of rotation and when a gear tooth  

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passes the sensor face. The display tracks the 
angle, and it's set up to count multiple turns  

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clockwise or counterclockwise.  

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As you can see, we're able to achieve 
resolution to thousandths of a degree.

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This thing's touchy because it's so precise.

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We hit the zero button 
whenever we want to set the index angle.  

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Here's the full circuit for this demo board. 

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Here's the microcontroller 
interface.

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And here's the analog LED interface.   

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Here's the firmware. We're running 
two four-digit displays in parallel  

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via I2C to get the full 
eight-digit display we want.

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So we have seen NVE's new ABT-Series TMR Gear Tooth 
Sensors have great performance advantages, with:

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* Low hysteresis for maximum repeatability;

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* Excellent linearity for high accuracy; 

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* Large output signals for 
simple analog interfacing;

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* Ultraminiature size to save your PCB board space;

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* And low noise to enable ultrahigh resolution.

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We've demonstrated a few thousandths 
of a degree with a 30-tooth gear.

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That means we'd be detecting single 
arcseconds with a 300-tooth gear.

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Design support is available on our Website, as 
well as datasheets and purchasing information.

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Click, email, or call for more 
information, or to buy NVE sensors today.

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♪♪