Gyro¶

Class Gyro is a subclass of EV3. You can use it to read values from a single LEGO gyro sensor (a gyroscope) without any knowledge of direct command syntax.

The gyro sensor is used to measure one-dimensional orientation and angular velocity. These attributes allow to get the measurements:

angle measures the current orientation as an angle, which is an integer representing the sensor’s clockwise rotation.

rate is an integer, representing the sensor’s clockwise rotation rate (or angular velocity) in degree per second.

state holds both, the current angle and the current rotation rate. It is of type GyroState.

If you like to use multiple gyro sensors simultaneously (e.g. to receive rotations along multiple axes), you can create more than one instance of this class.

Asking for the current orientation angle¶

Choose settings (protocol and host) to connect the EV3 to your computer. Replace the settings in the program below, connect a gyro sensor to PORT_1, run this program and rotate the gyro sensor:

from time import sleep
import ev3_dc as ev3

settings = {"protocol":ev3.BLUETOOTH, "host":"00:16:53:81:D7:E2"}
with ev3.Gyro(ev3.PORT_1, **settings) as gyro:
    while True:
        current_angle = gyro.angle
        print(f"\rThe current angle is {current_angle:4d} °", end='')
        if current_angle >= 360:
            print("\n" + "The sensor made a full clockwise turn!")
            break
        elif current_angle <= -360:
            print("\n" + "The sensor made a full counterclockwise turn!")
            break
        sleep(0.05)

Some remarks:

Mathematically, clockwise rotation is measured with negative values, counterclockwise rotation with positive ones. LEGO’s gyro sensor does not follow this convention! If you face the the red icon on its top, then clockwise rotation measures positive.
In the moment, when class Gyro is initiated, the sensor’s current rotation angle becomes value zero.
What a LEGO gyro sensor measures is not really orientation. Instead it measures the orientation angle between an original orientation and the current one. If the sensor made multiple full rotations, then angle will correctly show it. Modify the program and break the loop when at least 2 full turns have been made.
Every reference of property angle starts a new communication between the program and the EV3 device.
Method reset() allows to reset the zero position at any other time or to set the current angle to any other value.
Printing ‘\r’ (carriage return) returns to the beginning of the current line. This allows to print the same line again and again.
Switch on verbosity by setting attribute verbosity to value 1 and you will see the communication data. This will show you, that the measurements use mode 3, which is EV3-Gyro-Rate & Angle and get angle and rate as results.

Asking for the current rotation rate¶

Connect your EV3 device and your computer via USB cable, connect a gyro sensor to PORT_1, then run this program and rotate the gyro sensor:

from time import sleep
import ev3_dc as ev3

with ev3.Gyro(ev3.PORT_1, protocol=ev3.USB) as gyro:
    min_rate, max_rate = 0, 0
    print('for 10 sec. do some rotation movements')
    for i in range(100):
        cur_rate = gyro.rate
        min_rate = min(min_rate, cur_rate)
        max_rate = max(max_rate, cur_rate)
        sleep(0.1)
print(f'max. rate: {max_rate} °/s, min. rate: {min_rate} °/s')

Some remarks:

Every reference of property rate starts a new communication between the program and the EV3 device. This is why we use variable cur_rate (current rate) to hold the values.
Switch on verbosity by setting attribute verbosity to value 1 and you will see the communication data.

Asking for the current state (angle and rate)¶

Connect your EV3 device and your computer via USB cable, connect a gyro sensor to PORT_1, then run this program and rotate the gyro sensor:

import time import sleep
import ev3_dc as ev3

with ev3.Gyro(ev3.PORT_1, protocol=ev3.USB) as gyro:
    cs = gyro.state
    print(f'angle: {cs.angle:4d} °, rate: {cs.rate:4d} °/s', end='')
    for i in range(10):
        sleep(1)
        cs = gyro.state
        print('\r' + f'angle: {cs.angle:4d} °, rate: {cs.rate:4d} °/s', end='')
    print()

Some remarks:

Every reference of property state starts a new communication between the program and the EV3 device. This is why we use variable cs (current state) to hold the values.
Porperty state is of type GyroState, which has two attributes: angle and rate.
Printing ‘\r’ (carriage return) returns to the beginning of the current line. This allows to print the same line again and again.
Switch on verbosity by setting attribute verbosity to value 1 and you will see the communication data.

Reset the original orientation¶

Sometimes the orientation in the moment of class initialization is not the best point of reference. E.g. an algorithm for a balancing device is clearer coded, when the perfect balance becomes the point of reference. Method reset() allows to do exactly that.

Connect your EV3 device and your computer via USB cable, connect a gyro sensor to PORT_1, then run this program and don’t rotate the gyro sensor:

from time import sleep
import ev3_dc as ev3

with ev3.Gyro(ev3.PORT_1, protocol = ev3.USB) as gyro:
        print(f"The current angle is {gyro.angle} °")
        sleep(5)

        gyro.reset(angle=90)
        print(f"After resetting: The current angle is {gyro.angle} °")
        sleep(5)

        gyro.reset(angle=180)
        print(f"After another resetting: The current angle is {gyro.angle} °")
        sleep(5)

        gyro.reset()
        print(f"After resetting again: The current angle is {gyro.angle} °")

The output:

Some remarks:

Run the program again and do some rotation movements of the sensor while the sleeping. You will see the very same output, why?
Modify the program and do the sleeping between the resets and the measurements. Then start the program again and do some rotation movements of the sensor.