Product Introduction

ManualsBrandsHitechnic ManualsMagnetic Sensors / CompassMagnetic Compass (compatible with Lego Mindstorms NXT)

HiTechnic NXT Compass Sensor for LEGO Mindstorms NXT

Introduction

The NXT Compass Sensor contains a digital magnetic

compass that measures the earth’s magnetic field and

calculates a heading angle. The Compass Sensor connects to

an NXT sensor port using a standard NXT wire and uses the

digital I2C communications protocol. The current heading is

calculated to the nearest 1° and refreshed 100 times per

second.

The Compass Sensor is housed in a standard Mindstorms

sensor housing to match the other Mindstorms elements.

To test your new sensor, plug it into port 2 of your NXT and select View > Ultrasonic cm > Port 2. As you

swing the sensor around, you’ll notice that the readings will change from 1 – 179. (0 will display as

?????? while in View mode.)

Programming

Mindstorms NXT-G

The compass can be programmed using LEGO Mindstorms NXT Software Compass Block*. If the

Compass Block is not available you may also use the standard Ultrasonic Block.

*Note: The NXT Compass Block can be downloaded by going to the Downloads page.

Ultrasonic Block

If using the Ultrasonic Block to program the compass, configure the block to centimeter mode as shown.

The Ultrasonic Block can only return values from 0 to 250 so in order to return the full range of headings,

0 to 360, the heading value returned when using the Ultrasonic Block will be the current heading divided

by 2. For example, if the current heading is 220°, the value returned will be 110. North will return a value

Summary of content (5 pages)

PAGE 1
HiTechnic NXT Compass Sensor for LEGO Mindstorms NXT Introduction The NXT Compass Sensor contains a digital magnetic compass that measures the earth’s magnetic field and calculates a heading angle. The Compass Sensor connects to an NXT sensor port using a standard NXT wire and uses the digital I2C communications protocol. The current heading is calculated to the nearest 1° and refreshed 100 times per second.
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of 0, East, a value of 45, South, a value of 90 and West, a value of 135. To get the actual magnetic heading, simply take the number returned and multiply by 2. Compass Sensor Block The Compass Block is designed to support the HiTechnic Compass Sensor and supports all compass features. 1. This plug wires the number for which of your NXT’s ports are connected to the compass sensor. 2. This plug wires the number of the Action to be performed. 3.
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motors or batteries. See Calibrating the Compass Sensor below for more information. Compare Compares the Absolute Heading to the range set and sets the logic value to show if the value is inside or outside the range. See Using Range below for more information. Using Relative Reading Relative Reading makes it easy to stay on a selected heading. To use this feature select the Relative Reading action. Then enter a Target that is the heading you wish to maintain.
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Using Range The Compare lets you set a range and easily determine if you are inside or outside the range. The Components for using the Range function are; Inside Range / Outside Range: Select if you want to test for an Absolute Heading inside the range or outside the range. A: The lower limit of the range (0 – 359) B: The upper limit of the range (0 – 359) To use the Range function, set the lower and upper limit of your range and whether you want to test for inside or outside the range.
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The Sensor type field will contain “Compass”. The Mode control field may be set to 0x00 or 0x43 to define measurement mode or hard-iron calibrate mode. The Heading fields will return the currently measured heading during measurement mode operation. During hard-iron calibrate mode operation, this field will jam. The heading is obtained by reading location 0x42 to obtain the two degree heading and 0x43 to obtain the one degree adder.