Honeywell HMR3100 User Manual

HMR3100

SENSOR PRODUCTS

HMR3100

Digital Compass Solution

User’s Guide

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HMR3100

SENSOR PRODUCTS

INTRODUCTION

The Honeywell HMR3100 is a low cost electronic compassing solution for use in consumer electronics and personal
navigation products. Honeywell’s magnetoresistive sensors are utilized to provide enhanced reliability and accuracy
in a small, two-axis, solid state compass design. This compass solution is easily integrated into systems using a
simple UART interface and binary data format. Performance is optimized for a horizontal circuit board orientations.

SPECIFICATIONS

Characteristics Conditions

Min

Heading

Accuracy Level

Resolution 0.5 deg

Repeatability

Magnetic Field

Range Maximum Magnetic Flux Density

Resolution 6 milli-gauss

Electrical

Input Voltage Unregulated 2.6 3 5 volts DC

Current Normal Mode (Average)

Digital Interface

USART USART 9600.N.8.1 2400 9600 19200 Baud

Update Continuous or Polled - 2 20 Hz

Connector 8-Pin -

Physical

Dimensions Circuit Board Assembly 19 x 19 x

Weight 1.5 grams

Environment

Temperature Operating

0.1

Sleep Mode

Calibration

Storage

6.1

0

-40

Typ

± 5

± 3

± 2

0.2

7.3

4.5

-

-

Max

deg RMS

deg

gauss

0.5

1

17.3

mm

+70

+110

Units

mA

µA

mA

°C

°C

Circuit Description

The HMR3100 Digital Compass Solution circuit board includes the basic magnetic sensors and electronics to provide
a digital indication of heading. The HMR3100 has a Honeywell HMC1022 two-axis magnetic sensor on board. The
HMR3100 allows users to derive compassing (heading) measurements when the board is in a reasonably horizontal
(flat) position.

The HMR3100 circuit starts with the HMC1022 two-axis magnetic sensors providing X and Y axis magnetic sensing of
the earth’s field. These sensors are supplied power by a switching transistor to conserve power with battery operated
products. The sensor output voltages are provided to a dual operational amplifier and then to analog to digital

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HMR3100

SENSOR PRODUCTS

converters (ADC) onboard a microcontroller (µC) integrated circuit. The microcontroller integrated circuit periodically
samples the amplified sensor voltages, performs the offset corrections, and computes the heading. This
microcontroller also performs the external serial data interface and other housekeeping functions such as the
calibration routine.

The power supply for the HMR3100 circuit board is to be about a +3 to +5 volt range allowing the user to provide a
single lithium battery to logic level supply voltages. The power supply architecture is a single ground system for single
ended supply sources (+ and ground return).

Note the “North Arrow” printed on the HMR3100 circuit board top side. This is the mechanical reference for product
alignment purposes. When placed on the development kit’s RS-232 motherboard assembly, this arrow also points
toward the 9-volt batterypin block on the motherboard (away from the RJ-11 jack).

Pin Configuration

Pin Number Pin Name Description

1 VCC Power Supply Input

2 NC No Connection

3 RTS Ready To Send Input

4 NC No Connection

5 TXD Transmit Data Output

6 RXD Receive Data Input

7 GND Power and Signal Ground

8 NC No Connection

The HMR3100 board is 0.77” on each side with eight pins in groups of four spaced at 0.6” apart in wide-DIP format.
Seated height is approximately 0.275”. Pin 1 is the upper right pin in Figure 1
.

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HMR3100 Dimensions

Figure 1