Test Servos and the Ultrasonic Module

Before assembling, you need to test the servos and the ultrasonic module according to the following steps.

Test the Servo

Step 1: Insert SunFounder Nano board into the Servo Control Board.


The USB port should be at the same side with blue power supply terminal.


Step 2: Insert the battery to the battery cable.


And connect the battery cable to the expansion board.


Step 3: Connect four servos to pin 9 to pin 12 of the expansion board.


The yellow, red, and brown wires connect to Signal, VCC, and GND on the expansion board, respectively.


Step 4: Open the Test_robot.ino under this path of DIY_4-DOF_Robot_Kit_-_Sloth\Code\Test_robot.

Uncomment the line 16 (delete sign // to start the corresponding servo test code); the comment the line: //#define ULTRASONIC.


It is not recommended to uncomment both lines at the same time.


Step 5: Select the corresponding Board, Processor and Port.

  • Board: Arduino Nano.

  • Processor: ATmega328P. If the code cannot be uploaded successfully for a long time, it needs to be changed to ATmega328P (Old Bootloader).

  • Port: Random allocation. The corresponding option can be determined by pulling out the USB cable and reconnecting the nano. Usually a combination of “COM + Numbers”.


Step 6: Upload codes to SunFounder Nano board.


After waiting for a few seconds, the download process is successful. The following window will prompt “Done uploading”.



If the code cannot be uploaded successfully for a long time, Processor needs to be changed to ATmega328P (Old Bootloader).

Step 7: Slide the power switch to ON. You will see the rocker arm rotates within 0-180 degrees, indicating the servo can work.


Test the Ultrasonic Module

  1. Connect Ultrasonic module to Servo Control Board via 4-Pin Anti-reverse Cable.

  1. Open the Test_robot.ino and select Board, Processor and Port.

  2. Comment out line 16 by prefixing #define SERVO with //; then uncomment #define ULTRASONIC.

  1. Open the serial monitor after uploading the code.

  1. Set the baud rate to 115200 (started by line 25 serial.begin(115200)).

  1. Turn the power switch to ON you can see the detected distance.


The detection distance of ultrasonic module is 2-400cm, if the data is 0 or a few thousand, it means that it is invalid data need to be ignored.