Sloth - SunFounder DIY 4-DOF Robot Kit¶

This cute learning kit focuses on the popular open source platform Arduino. You can learn the knowledge of the Arduino servo and ultrasonic ranging module by applying this kit.

It is a new mobile robot called Sloth developed by SunFounder. Each leg has 2 joints driven by servo. One 9V chargeable lithium batteries are to supply the bot when the SunFounder Nano is used as the control board, compatible with the Arduino Nano. A servo control board connects with the batteries, servos, SunFounder Nano, and the HC-SR04 ultrasonic ranging module. Sloth can move forward and detect the range to make a turn when encountering an obstacle. In addition, when learning to program, you can also have the fun to build a pretty cool bio-robot by yourself.

Components¶

Structural Plate

Note

Please check the structural plate and component list, if there misses any components, please take pictures of all the components you have received and inform us of the missing parts，and send E-mail to service@sunfounder.com.

Mechanical Fasteners

Electrical Components

Battery（Not Included）

Download the Code¶

We have uploaded the relevant code material to github, you can download it through the link below.

Sloth

Then, you can see 2 folders.

DIY_4-DOF_Robot_Kit_-_Sloth: It is recommended to download this package first, including the Arduino code, drivers, library, schematic and user manual.
How_to_use_Sloth_with_Mixly: This is an extended use of Sloth via graphical programming software - Mixly to program. The manual contains only a basic introduction to Mixly and how to program in Mixly, but does not include hardware assembly part, you need to check Assembly first, and after Sloth is completely assembled, you can use Mixly for programming.

Install Arduino IDE and Add Libraries¶

The Arduino IDE, known as Arduino Integrated Development Environment, provides all the software support needed to complete an Arduino project. It is a programming software specifically designed for Arduino, provided by the Arduino team, that allows us to write programs and upload them to the Arduino board. The Arduino IDE 2.0 is an open-source project. It is a big step from its sturdy predecessor, Arduino IDE 1.x, and comes with revamped UI, improved board & library manager, debugger, auto complete feature and much more. In this tutorial, we will show how to download and install the Arduino IDE 2.0 on your Windows, Mac, or Linux computer.

Download Arduino IDE¶

The code in this kit is written based on Arduino, so you need to install the IDE first. Skip it if you have done this. Now go to the Arduino website: https://www.arduino.cc/en/software, find the one that suits your operation system and click to download.

Installation¶

Windows - Win 10 and newer, 64 bits
Linux - 64 bits
Mac OS X - Version 10.14: “Mojave” or newer, 64 bits

Windows¶

Double click the arduino-ide_xxxx.exe file to run the downloaded file. Read the License Agreement and agree it.
Choose installation options.
Choose install location. It is recommended that the software be installed on a drive other than the system drive.
Then Finish.

Mac OS X¶

Double click on the downloaded arduino_ide_xxxx.dmg file and follow the instructions to copy the Arduino IDE.app to the Applications folder, you will see the Arduino IDE installed successfully after a few seconds.

Linux¶

For the tutorial on installing the Arduino IDE 2.0 on a Linux system, please refer to: https://docs.arduino.cc/software/ide-v2/tutorials/getting-started/ide-v2-downloading-and-installing#linux

Open the IDE¶

When you first open Arduino IDE 2.0, it automatically installs the Arduino AVR Boards, built-in libraries, and other required files.

In addition, your firewall or security center may pop up a few times asking you if you want to install some device driver. Please install all of them.

Now your Arduino IDE is ready!

Note

In the event that some installations didn’t work due to network issues or other reasons, you can reopen the Arduino IDE and it will finish the rest of the installation.

Add Libraries¶

You will get the following error when trying to run the code that contains the ultrasonic module:

NewPing.h: no such file or directory

Therefore, it needs to be manually added. Here are the steps. Open the Arduino IDE, click on the Library Manager icon to open it, search for newping and click on INSTALL in the options that appear. Wait for the prompt to complete the installation and you’re done!

Test Servos and the Ultrasonic Module¶

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

Test the Servo¶

Warning

Due to an unfortunate manufacturing error, the polarity of some battery connectors has been reversed, which may cause overheating when using 9V battery.

To prevent any safety risks or damage to the product, please carefully check the polarity of the battery connectors before inserting a 9V battery.

If you find that the battery connector is reversed, please do not attempt to complete the installation. Instead, please contact our customer support team. We will replace it for you as soon as possible.

Email: cs@sunfounder.com

Insert SunFounder Nano board into the Servo Control Board.

Note

The USB port should be at the same side with blue power supply terminal.
Insert the battery to the battery cable.
And connect the battery cable to the expansion board.
Connect four servos to pin 9 to pin 12 of the expansion board.

Note

The yellow, red, and brown wires connect to Signal, VCC, and GND on the expansion board, respectively.
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); then comment the line: //#define ULTRASONIC.

Note

It is not recommended to uncomment both lines at the same time.
The Arduino IDE may not recognize your board if you see Unknown COMXX when selecting a board here.
After clicking on Unknown COMXX, the Select Other Board and Port pop-up will appear. Type nano in the search box, then select Arduino Nano and click OK to confirm.

Note

It doesn’t matter if your Arduino Nano is greyed out, it means you don’t have the Arduino AVR Boards core installed, just select it here and click OK to install it automatically.
Now you will be able to see the Arduino Nano board being recognized.
Upload codes to the Nano board. After a few seconds, the “Done uploading” message will appear.
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¶

Connect Ultrasonic module to Servo Control Board via 4-Pin Anti-reverse Cable.
Open the Test_robot.ino and select Board, Processor and Port.
Comment out line 16 by prefixing #define SERVO with //; then uncomment #define ULTRASONIC.
Open the serial monitor after uploading the code. Set the baud rate to 115200 (started by line 25 serial.begin(115200)).
Turn the power switch to ON you can see the detected distance.

Note

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.

Assembly¶

Head Assembly

Insert the ultrasonic module into No. 1 board and secure it with M1.4*8 screws and M1.4 nuts.

Use a M3*5 screw to secure the M3*8 Bi-pass Copper Standoff post on No. 1 board.

Electrical Module Assembly

Use a M3*5mm screw to mount the previously installed circuit board on No. 1 board.

Use M3*5 screws to fix M3*25 Bi-pass Copper Standoff under the No. 1 board.

Servo Assembly

Use M2*8 screws and M2 nuts to mount the servo on the corresponding position on the No. 2 board. (Note the direction of the servo installation)

Secure the No. 1 and No. 2 boards with M3*5 screws. Note that the side of the servo shaft should be mounted on the side of the USB port.

Use two M1.5*5 self-tapping screws to fix the 2-arm rocker arm to the No. 4 board and use the same method to install another No. 4 board.

Secure one of the round holes on the 4th and 5th boards with M3*8 Countersunk screws and M3 self-locking nuts.

Use the same method to secure the other round hole on the 4th and 5th boards, as shown in the following figure:

Use two M1.5*5 self-tapping screws to secure the 1-arm rocker arm on the No.4 board.

Install another No.4 board in the same way.

Turn the No. 6 board with the countersunk side down and secure the No. 6 board to the right leg described above with the M3*8 countersunk screw and the M3 self-locking nut.

The same method can be used to secure the No.7 and the left leg. Observe the picture carefully. The left and right feet you have installed need to be exactly the same as that in the picture. Otherwise, the robot won’t walk properly.

Servo INSTALL Test

Warning

Due to an unfortunate manufacturing error, the polarity of some battery connectors has been reversed, which may cause overheating when using 9V battery.

To prevent any safety risks or damage to the product, please carefully check the polarity of the battery connectors before inserting a 9V battery.

If you find that the battery connector is reversed, please do not attempt to complete the installation. Instead, please contact our customer support team. We will replace it for you as soon as possible.

Email: cs@sunfounder.com

Connect the 4 servos to pin 9, 10, 11 and 12 respectively again. This is designed to keep the servo angle of the upload code at 90°(internal angle) before the servo shaft is installed, in order to let the Sloth remain upright after assembly.

Open the program simple_robot.ino under the path of DIY_4-DOF_Robot_Kit_-_Sloth\Code\simple_robot. After opening, you can see the other 2 files: VarSpeedServo.cpp and VarSpeedServo.h are opened at the same time. This two files are set to adjust the angle of the servo.

There are three #define statements in line 39-41. Removing the respective comment signs // enables you to start their functions as shown.

#define INSTALL: Start the INSTALL mode, in which 4 servos will be fixed at 90°for assembly.
#define CALIBRATION: Start the calibration mode, in which the angles of 4 servos can be adjusted.
#define RUN: Start the RUN mode, in which the robot can go ahead and get round if it meets obstacles.

Note

Only one function can be used at the same time. Starting multiple functions might break down the robot.

In the current step, use INSTALL mode. Then select the corresponding Board, Processor and Port. The code is then uploaded into the SunFounder Nano board. Don’t forget to toggle the power switch to ON. When the servo control board is powered on, the servo will rotate to the position specified by the program.

Foot Assembly

Note

Keep on the power until the whole step.

Assemble the left leg with the smallest screws in the packaged with servo, a gasket plate is needed between the servo and left leg. Try to keep the edges of the 4th board and the servo parallel to each other. If deviation are found at installation, it is normal and we will adjust them later when calibrating.

Insert a servo (in working condition) into the servo shaft of the left foot. Besides 2 M2*8 screws and 2 M2 nuts, a gasket plate is needed between the servo and left leg.

Assemble the right leg in the same way.

Secure the 2 legs with the smallest screws in the packaged with servo.

Battery Assembly

Attach one side of velcro tape to the bottom of the No. 1 board and the other side to the battery.

Insert the battery into the battery cable and plug the other end into the expansion board.

Lastly, paste the battery on the No. 1 board.

Servo CALIBRATION Test

Check the assembly of the 4 servos according to the picture as shown.

Open the program simple_robot.ino and go to Line 39. Set #define CALIBRATION as able and disable the other two. Then select the correct board and port, and upload the sketch.

If the robot is not fully upright, the angle can be manually calibrated. Go to Line 15 to rectify it.

The basic principle of calibration: increased values can rotate the servo shaft clockwise and vice versa. For example, if the right leg is toe out, you need to decrease the upper-right servo’s angle; if it is toe in, you need to increase the angle.

Tips for calibration: #. The calibration method for the left leg works the opposite way for right leg. #. If the right foot’s sole faces outward, you need to decrease the lower-right servo’s angle; if its sole faces inward, you need to increase the angle. #. The calibration method for the left foot works the opposite way for right foot.

Ultrasonic Connecting

Connect pin TRIG of the ultrasonic to pin 4 of the board, ECHO to pin 3, VCC to VCC and GND to GND.

Wire Arrangement

Twine the servo wire and 4-Pin anti-reverse cable on the No. 1 board.

So far the robot has been assembled successfully, it’s easy if you follow our steps closely. Hope you enjoy the fun of the bot, thanks for watching.

Example¶

Here, we provide you with two sample programs to play Sloth:

Simple Robot¶

In this code we write mobile obstacle avoidance for the robot. After the program is burned, sloth will go straight ahead. If it senses an obstacle ahead, it will step back and turn to find a new direction.

Open the program simple_robot.ino under the path of DIY_4-DOF_Robot_Kit_-_Sloth\Code\simple_robot.

(This is also the program what we use to install and calibrate the servo.) Go to Line 39 again, set #define RUN as able and disable the other two, then upload the code to the SunFounder Nano board.

After burning successfully, unplug the USB cable and slide the power switch to ON.

You will see the robot moving forward. When encountering an obstacle, it will make a turn and then go forward again.

Dancing¶

In this code, we write the basic actions of sloth and compose them into a dance. Open the program Dancing.ino under the path of DIY_4-DOF_Robot_Kit_-_Sloth\Code\Dancing. Go to Line 196, select the RUN function by rectifying #define.

After burning successfully, unplug the USB cable and press the power button on the servo control board. You will see the robot dancing.

Note

The program also needs to be calibrated in the same way as Servo CALIBRATION Test in Assembly. If there has been a precise calibration, you can modify the parameters in line 22 directly.

Q&A¶

Q1: How can we know the servo is damaged?

In Servo Test step, if the servo rocker arm shake, get stuck or can not rotate smoothly, with an abnormal sound, we can judge it as a damaged one.

Q2: Why the Sloth reboots in running?

If the Sloth is in lower power, rebooting will happen, please charge the battery in time.
It could be the servos are lacking for power. Open the program and go to Line 12, 13. vel is the servos rotating speed in initialization or moving forward; vel_Back is the servos rotating speed in moving backward; delay_Forward, delay_Back are the delays between two moving forward loops and moving backward loops.
- If rebooting happens in moving forward actions, you can decrease the value of vel and increase the value of delay_Forward. For example, decrease vel value to 10, and increase delay_Forward to 1500.
- If rebooting happens in moving backward actions, you can decrease vel_Back and increase delay_Backward. For instance, decrease vel_Back to 8, and increase delay_Backward to 1500. You can adjust to a proper value as you want. Then click Upload.

Q3: Sloth walks too slowly when it moves forward. How to solve this?

A3: Sloth’s default speed is middle speed, the related sketch is vel(mid), delay_Forward(mid) = (20, 750). You can change the speed value as shown below to adjust the walking speed.

change the value of vel and delay_Forward in line12 and 13 to as shown:

vel = 50, delay_Forward = 500

Then click Upload.

Note

If you adjust the robot to a high walking speed, it may fall down and break. Thus it’s better to do some protection for the Sloth.

Q4: Sloth walks too slowly when it moves backward. How to solve this?

Considering the structure of Sloth, it’s better do adjust a slow speed for backward walking. If you want to adjust the walking speed, refer to Q3 to adjust the value. DO NOT adjust a high speed for walking backward to avoid possible falling down.

Q5: How to make the sloth more stable in walking?

Cut to get two paper cushion for the robot feet, and stick them on the Sloth soles to maintain enough friction for a stable walking.

Q6: What is macro definition (``#define``)?

The #define creates a macro, which is the association of an identifier or parameterized identifier with a token string. After the macro is defined, the compiler can substitute the token string for each occurrence of the identifier in the source file.

You can use the #ifdef directives anywhere #if can be used. The #ifdef identifier statement is equivalent to #if 1 when identifier has been defined. It’s equivalent to #if 0 when identifier hasn’t been defined, or has been undefined by the #undef directive. These directives check only for the presence or absence of identifiers defined with #define, not for identifiers declared in the C or C++ source code.

In sloth code, we use #define and #ifdef to start corresponding functions.

Q7: Why is my sloth not working and the battery is getting hot?

Warning

Due to an unfortunate manufacturing error, the polarity of some battery connectors has been reversed, which may cause overheating when using 9V battery.

To prevent any safety risks or damage to the product, please carefully check the polarity of the battery connectors before inserting a 9V battery.

If you find that the battery connector is reversed, please do not attempt to complete the installation. Instead, please contact our customer support team. We will replace it for you as soon as possible.

Email: cs@sunfounder.com

Summary¶

In this manual, having learned the related components for building the robot kit, you’ve gone through the assembly of the mechanical parts and electrical modules with the knowledge of Arduino as well as a brief introduction of the key parts like servo, ultrasonic, etc. Also you’ve got a lot of software and coding, which lays a solid foundation for your futrue journey of exloring open-source field.

The SunFounder DIY 4-DOF Robot Kit is not only a toy, but more a meaningful development kit for Arduino. After all the study and hands-on practice of the kit, you should have a better understanding of Aduino. Now, get started to make better work!

Copyright Notice¶

All contents including but not limited to texts, images, and code in this manual are owned by the SunFounder Company. You should only use it for personal study, investigation, enjoyment, or other non-commercial or nonprofit purposes, under the related regulations and copyrights laws, without infringing the legal rights of the author and relevant right holders. For any individual or organization that uses these for commercial profit without permission, the Company reserves the right to take legal action.