Acc_Gyro Projects:
Using Acc_Gyro Board with Arduino. Simplified Kalman Filter.
A Guide To using IMU (Accelerometer and Gyroscope Devices) in Embedded Applications.
Quadcopter Design using Acc_Gyro

Overview

The Acc_Gyro Board represents a 5DOF Inertial Measurement Unit (IMU), capable of measuring acceleration on all 3-axis as well as measuring rotation rate around the X and Y axis. Combining values from both accelerometer and gyroscope will allow you to obtain accurate values of inclination angles relative to the earth's surface (see Starlino's IMU guide). IMU units are often used in projects like gaming devices, balancing robots and UAV.

The Acc_Gyro board combines the LIS331AL (datasheet) - a 3-axis 2G accelerometer and LPR550AL (datasheet) - a dual-axis pitch and roll, 500deg/second gyroscope. The Accel_Gyro also features a 3.3V voltage regulator, so it can be powered with power sources in range of 3.3V to 6V. The onboard low-pass filters ensure a cleaner signal, while the high pass filters compensates for gyro drift normally associated with this type of devices.

The Acc_Gyro is also available without the gyroscope - the gyroscope pins are unconnected, but all the filtering components are in place so you can simply upgrade later to full functionality with a single gyroscope chip. On the other hand, if you're sure you don't need the gyro functionality you can safely cut the board along the line that goes between pins 3V3|HP and NC6|NC7.

Core Specifications

Accelerometer Module
Acceleration range: +/- 2g
Sensitivity: 478.5 mV/g
Zero-g-level: 1.65V
Low pass filter(noise reduction): 50Hz

Gyroscope Module
Measured range:
GX4,GY4: 4x (amplified) +/- 500deg/sec
GXF,GYF: 1x(non-amplified) +/- 2000deg/sec
Sensitivity:
GX4,GY4: 4x (amplified) 2 mV/Deg/sec
GXF,GYF: 1x (non-amplified) 0.5 mV/Deg/sec
Zero-rate level: 1.23V
High pass-filter (drift compensation): 0.16Hz
Low pass-filter (noise reduction): 160Hz

Supply current: ~10mA
Supply voltage: 3.3V to 6V

* Values are typical. Please consult sensor data sheets for tolerance info.

Dimensions

Pinouts


Full pinout information is available in PDF format (pdf), but to summarize:

P13: GYF, Gyro non-amplified, filtered Y-axis Output
P15: GY4, Gyro amplified (x4), Y-axis Output
P16: VREF, Gyro Reference Voltage (1.25V, fixed)
P17: GX4, Gyro amplified (x4), X-axis Output
P18: GXF, Gyro non-amplified, filtered X-axis Output
P26: ST, Gyro self test (logic 0 = normal, 1 = self test mode)
P27: PD, Gyro power down (logic 0 = normal, 1 = power down mode)
P28: HP, Gyro high pass filter reset (logic 0 = normal, 1 = Reset HP filter)

P29: 3V3, Voltage regulator output (3.3v)
P30: Supply Voltage input, 5v
P31: GND, Ground

P32: AZ, Accelerometer Z-axis analog filtered output
P33: AY, Accelerometer Y-axis analog filtered output
P34: AX, Accelerometer X-axis analog filtered output

Schematic


Click here for a hi-res version (pdf)

Using the board

You're probably planning on using the Acc_Gyro board with your favorite microcontroller. The module outputs analog voltage on its output pins so your MCU must have an ADC module or you might use and external ADC chip.

Power

There are 2 ways to power the device.

If your project has a power source in the range of 4V-6V you can power the device by applying power to pins P30(5V), P31(GND). In this case pin P29(3V3) will output 3.3V from internal voltage regulator that you can use for powering other low-power devices (do not exceed ~40mA).

If your project already has a stable 3.3V power source you can apply power directly to pins P29(3V3),P31(GND). Do not apply any power to pin P30(5V) in this case!

Please note that pins ST,PD,HP are designed for logic levels of no more than 3.3V. They are normally pulled to ground using 10K resistors (already present on Acc_Gyro board), so normally you can leave them unconnected. If you plan on using these pins in a 5V project, please use a logic level converter. A simple solution is to use a 5K resistor in series with your 5V outputs.

Gyroscope Module


Download PDF of Gyroscope Guide

When the gyro is not moving, GYF, GY4, GXF, and GX4 will all output something around 1.23V (zero-rate level).

As the board rotates, the output voltage will change at a linear rate. A clockwise rotation in YZ plane (around X axis) will cause GYF, and GY4 to increase in voltage output. Rotating clockwise at 500deg per second will cause the voltage to increase to 1.48V on GYF, and 2.23V on GY4. A counter-clockwise rotation will decrease voltage output - 500deg per second of counter-clockwise rotation will cause the voltage to decrease to .98V on GYF and .23V on GY4. The relationship is linear - every degree per second of rotation will cause a 2mV change on GY4, and a 0.5mV change on GYF. Clockwise rotation causes an increase in voltage and counter-clockwise causes a decrease in voltage, relative to the stable voltage output of 1.23V

Same deal with rotation in XZ plane (around Y axis) - the stable voltage output is 1.23V, clockwise rotation cause an increase in voltage of 2mV per degree/second on GX4 and .5mV on GXF.

Accelerometer Module


Download PDF of Accelerometer Guide

Note: Voltage values are for reference only. There could be up to a maximum of +/-6% aberration according to LIS331AL datasheet. For maximum precision please measure and use actual offset values before using device in a project.

While the gyroscope measures rotation, the accelerometer measures acceleration on several axis. If you set the Acc_Gyro board on the table as shown in the photo above, the Z axis will experience 1G and AZ will output 1.17V. The X and Y axis' don't have gravity pulling on them, they're at 0G, and will output 1.65V.

If you put it on the table upside down, the X and Y axis' would still have 0G of acceleration, so you'd get AX = 1.65V, AY = 1.65V, and AZ = 2.13V. The Acc_Gyro board is capable of measuring accelerations of +/-2G (+/-19.6m/s^2) along any axis. 2G is the same as going from 0 to 44mph in 1 second. When an axis experiences +2G, it will increase voltage to 2.6V. When it experiences -2G, it will decrease voltage to .7V.

Please note that gravitation force (directed from sky to ground) has same effect on the device as if you would accelerate the device in an opposite direction, in a place with no gravitation field. So keep this in mind if you're planing to use the device for something like measuring the acceleration of your car or bike.

The module comes pre-assembled, although you'll need to add pin headers to the edge of the board to connect to a breadboard or Protoboard. Pin headers are no longer included, but you can add it to your cart separately.