Arriving to Lakeview last Wednesday for class, the City Walls group said hello to the usual assortment of professors, both in person and digital. Professor Fred Briggs came on the screen:

“Today, we are working with Arduinos to understand their functionality and how they will serve different purposes with a drone.”

Instructors give technical lecture on coding arduinos. Key points target growth from interdisciplinary perspectives.

Instructors give technical lecture on coding arduinos. Key points target growth from interdisciplinary perspectives.

Our group of six listened to a lecture with a joint focus on Arduinos and ESC’s. Arduinos are used on UAV’s as the platform for sending and receiving code in congruence with the small, yet integral part of many UAV’s known as an ESC, or Electronic Speed Controller. This device controls how fast the motor spins, with three groups of wires connecting to the motor, the battery, and the receiver or Arduino board.

For practice purposes, the team set up with the motor and propeller below, rather than the actual drone.

Of the three wires coming from the ESC, one is normally black and hooked to the ground pin labeled as GRD on the board. Attaching this wire is a necessary first step as it grounds, or establishes, the connection between ESC and Arduino board. Another wire, usually red, is hooked to the 5V pin, and the last wire, usually white, is hooked to the pin later labeled in the Arudino code as MOTOR_PIN. In this case, City Walls used pin number 9 to set a location on the Arduino board that could receive command signals from our code.

Arduino parts labeled: Arduino board, battery, motor and propeller, electronic speed controller.

Arduino parts labeled: Arduino board, battery, motor and propeller, electronic speed controller.

 

Armed with the devices above, the team set up with a tablet to input code for calibrating the ESC, shared by our professors via PowerPoint and easily accessed on the Arduino website. The team began manipulating the code to set various commands such as speed of the motors, frequency of propellers, and start or stop time of both.

The City Walls Team is close-knit and goofy. Look at those grins! (Missing: Kiva Gayle)

The City Walls Team is close-knit and goofy. Look at those grins! [Not pictured: Kiva Gayle]

The greatest challenge for the class as a whole was coding for the right amount of power being sent to the motors, connected through a wire from the ESC. MAX_SIGNAL and MIN__SIGNAL were the portions of the code which determined this power. For the rest of the class it was common to hear the sounds of propellers whirring to extreme speeds as everyone worked to figure out the best power levels.

After one poorly timed computer restart and some trial and error, City Walls team determined the functionality of the motors and uploaded the code to our Arduino board. When connected to the ESC, the Arduino board signaled to the motors through Pulse Position Modulation, or PPM. Pulses traveled through the three wires connecting the ESC and the Arduino board and the team watched as our propeller started spinning.

Success! As the City Walls Team looks towards the most effective methods for scanning and archiving Cartagena’s historic city walls, understanding basic commands and programming of the UAV will allow for the most creative approach. Stay tuned for more developments from City Walls!

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