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Hello.
Today we're demonstrating NVE's ABT-Series,
a new line of tunneling magnetoresistance gear tooth sensors. We'll achieve resolution
down to a few thousandths of a degree of a rotation with these precise new sensors.
ABT-Series gear-tooth sensors are manufactured with NVE's state-of-the-art TMR technology,
which has fundamental sensitivity advantages over Hall-effect, AMR, and even our own legacy GMR
products. ABT sensors are dual-channel sensors consisting of two passive Wheatstone bridges.
They are typically used in conjunction with small ceramic magnets in a back-biasing
configuration, most easily achieved by placing the magnet behind the sensor
on the reverse side of a printed circuit board. The magnet generates a source of magnetic field,
which enables the sensor to detect gradients from passing metal objects.
ABT-Series sensors detect only the horizontal component of magnetic field in the plane
of the sensor package, so they need to be pitch-matched to the target gear for optimal
performance. Standard ABT-Series products cover a wide range, from tiny pitch gears
found in miniature robotics up to larger gears found in automotive applications.
Here's the demo board. We're using an ABT375-00E sensor to detect
a 30-tooth, 0.5-module carbon steel gear. The ABT375 sensor is
back-biased with a small ceramic magnet,
following the recommendation in the product datasheet.
The sensor outputs run to two separate signal processing circuits.
The first circuit amplifies the sensor outputs before feeding into the ADC channels
of an inexpensive ATTINY85 microcontroller. The microcontroller calculates
the angle and displays the result on an eight-digit display.
Since this is an incremental encoder,
we also added a zero button to set the zero angle when the circuit is powered.
The second circuit uses a comparator to generate digital A and B pulses directly from
the unamplified sensor outputs. The A and B pulses are about 90 degrees apart, since we matched the
pitch of the sensor to the gear according to the datasheet. Therefore we can use a simple flip-flop
to generate a direction indicator, in addition to the tooth detection the A or B pulse gives us.
We'll turn on the power.
The angle is displayed in degrees with three decimal places of resolution.
As we turn the gear, the LEDs indicate the direction of rotation and when a gear tooth
passes the sensor face. The display tracks the angle, and it's set up to count multiple turns
clockwise or counterclockwise.
As you can see, we're able to achieve resolution to thousandths of a degree.
This thing's touchy because it's so precise.
We hit the zero button whenever we want to set the index angle.
Here's the full circuit for this demo board.
Here's the microcontroller interface.
And here's the analog LED interface.
Here's the firmware. We're running two four-digit displays in parallel
via I2C to get the full eight-digit display we want.
So we have seen NVE's new ABT-Series TMR Gear Tooth Sensors have great performance advantages, with:
* Low hysteresis for maximum repeatability;
* Excellent linearity for high accuracy;
* Large output signals for simple analog interfacing;
* Ultraminiature size to save your PCB board space;
* And low noise to enable ultrahigh resolution.
We've demonstrated a few thousandths of a degree with a 30-tooth gear.
That means we'd be detecting single arcseconds with a 300-tooth gear.
Design support is available on our Website, as well as datasheets and purchasing information.
Click, email, or call for more information, or to buy NVE sensors today.
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