Assembling DIY robot kits is one of my favorite hobbies. You start with a box full of components organized in small plastic bags and end up with a mounting structure and several spare bolts!

In this tutorial, I present how to assemble a kit of a 17 degrees of freedom (DOF) humanoid biped robot, which has 17 servomotors: three in each arm, five in each leg, and one for the head.

This type of robot can be used as both a children's toy (for kids over 12 years who want to become familiar with robotics, mechanics, electronics, etc.) and for young people and adults who want to get more involved in software programming. It can even be used as a platform for research and development. While you may not be able to make a robot that practices parkour like Atlas, you can try to make your robot walk, imitate movements, or even play soccer!

In this tutorial, I present only how to assemble the kit and use the basic software, but the possibilities of control and programming are numerous (and can be explored in future projects).

About the kit: In this project, I used the Sainsmart kit.

Merits:

• Quality of the parts: the structure of the robot is entirely aluminum and presents good mechanical resistance. The material is susceptible to scratches during assembly but will hardly bend or break.
• Spare parts: the kit comes with several spare bolts and nuts. It is reassuring to know that a lost screw won't prevent you from finishing the assembly of the robot!
• Tools: all necessary tools for assembly are included in the kit. You do not need any additional equipment (unless you want to do some welding, as in my case).
• Electronic components: both the servomotors and the control board have been shown to be of excellent quality. The kit even comes with a remote control that can be used to control the movements of the robot, which wasn't explored in this tutorial.
• Software included: for beginners, the software provided by the manufacturer will help you to test simple movements and program sequences of movements without needing any programming knowledge!

Flaws:

• Documentation: the kit doesn't have good documentation available online, which can be a bit frustrating at first. Some parts of the manual are only available in Chinese and often refer to kits other than the one used here.
• Parts missing: despite the spare parts, it could come with a few more spacers to mount the circuit and the front structure of the robot's body.
• Power supply: The kit does not come with batteries or a specific power supply for powering the motors (between 5 and 7.4V). It took some time to get the batteries right for the project.

Step 1: Tools and Materials

The following tools (find links from the original article) and materials were used in this tutorial:

• SainSmart 17-DOF Biped Humanoid Kit: This awesome kit has everything you need to build a humanoid robot: 17 servos, metal structure, bolts, nuts, etc. It already comes with the tools needed for assembling the chassis, which is great for beginners! Electronics and cables are also included.
• Soldering iron and wire: You'll eventually need it to solder the battery pack and the on/off button. So consider having a good soldering iron and wire nearby.
• 18650 3.7V batteries (x4): I used these to power the whole circuit. These servos use between 5 and 7.4V. I used two 3.7V batteries in series for powering them and two packs in parallel for more current.
• 2S 18650 battery holder (x2): It can hold two 18650 batteries in series and can be easily attached to the back of the robot.
• 18650 battery charger: Your batteries will eventually run out of power. When that happens, a battery charger will come to your rescue.

Step 2: Arms

Assembling the robot arms is the easiest and quickest part.

The following parts will be used on each arm:

• U-shaped profile (x2)
• C-shaped profile (x2)
• Hand (x1)
• Servos (x2)
• Bolts (x10)
• Nuts (x8)
• Screws (x14)
• Disk-type servo horns (x4)

The video above illustrates how to do the assembly.

For each arm, the following steps should be performed:

1. Attach one pair of U-shaped profiles (back-to-back) using four bolts and nuts. Use the Phillips screwdriver in the kit to tighten the screws. In the end, you will have a profile in the shape of H.
2. Fit a servomotor inside on one side of the H-shaped profile. Fix the motor using seven screws—three on the side of the servo motor with the metal shaft and another four on the side of the servomotor with the plastic shaft.
3. Fit the second servomotor to the other end of the H-shaped profile, similar to the previous step. Position the servos so that both have the metal axis facing the same side.
4. Fit the servo drive horn to the axes. Use the appropriate discs (with some internal teeth) and screws for fixing on the metal shafts. The discs on the plastic side are free.
5. For wrist mounting, connect the metal profile of the hand to the C-shaped profile using four screws and nuts.
6. Attach the hand to one end of the arm. The C-shaped profile must be connected so that its two ends fit externally on the two discs of one of the servos. Align the holes and secure with three screws on each side.
7. Repeat the steps above for the other arm.

In the next part, I show you how to mount the robot's legs.

Step 3: Legs

The mounting of the legs of the robot is the most time-consuming part due to the number of motors used. The following parts are used on each leg:

• Foot (x1)
• C-shaped profile (x5)
• U-shaped profile (x2)
• Hips (x1)
• Servos (x4)
• Bolts (x44)
• Nuts (x16)
• Screws (x25)
• Disk-type servo horns (x8)

The video above shows how to assemble the legs. The following steps must be performed:

Attach the first servomotor to the foot of the robot. The servo fits in the center of the foot (there will be a rounded part for the shaft socket) and must be secured using six screws (three on each side).

Place a horn on each side of the servo, remembering that the disks are different for the plastic and metal shafts.

Join two C-type profiles (back-to-back) with a rotation of 90 degrees with respect to each other. Use four bolts and nuts to connect these two parts. After mounting, this piece will be used in the ankle of the robot.

Attach the ankle to the servomotor installed at the foot of the robot. One of the C-shaped profiles should be attached to the two servo disks using three screws on each.

For the leg and thigh of the robot, the same type of assembly will be used. For the leg, attach a C-shaped profile to a U-shaped profile using four bolts and nuts. A servomotor should be placed inside the end where the U-profile is and secured with seven screws (three on the metal shaft side and four on the opposite side). Repeat this assembly twice.

Connect the ankle to the leg of the robot. The servo of the leg should be connected to the free end of the C-shaped profile at the ankle, using six screws for connection between the two parts.

The thigh assembly should be performed in the same way as the leg, connecting the existing servo in the thigh to the free end of the C-profile of the leg.

To connect the leg to the body (shown in the next step), it will be necessary to mount the hip. Connect the hip (rectangular part) to a C-shaped profile using four screws and nuts.

A servo must be connected facing the hip piece. This part has a rounded cavity to fit the servo shaft. Use six screws to secure the servo. Then connect the horns to the axles using screws when necessary.

Lastly, connect the hip to the thigh, just as in the previous sections.

In the next step, I present how to mount the body of the robot and perform docking of the arms and legs.

Step 4: Body

Mounting the body is the last part before you can start playing with the electronics. It's a quick process!

The following parts are used here:

• Plain body part (x2)
• Rounded body part (x1)
• C-shaped profile (x2)
• Servos (x4)
• Bolts (x24)
• Screws (x25)
• Disk-type servo horns (x8)

The video above shows how to assemble the body.

To assemble it, the following steps must be performed:

1. The body assembly starts by fixing the four servo motors in the body structure (flat triangular-shaped aluminum part). Install two motors on each shoulder and two motors on the pelvis using screws for fastening.
2. Install the second body plate on top of the servos, using screws for fixing. Pay attention to the screws on the inside, close to the shoulders.
3. Place the horns on the four servos, using screws in the gears.
4. A C-shaped profile must be attached to each shoulder using four screws to attach it to the servo horn.
5. Position the robot arms, fitting them onto the C-shaped profile at the end of each leg to the motors of the pelvis. Secure the legs using six screws.
6. Position the arms, fitting the servo at the end of each arm to the C-shaped profile of the robot's shoulder. Attach them using six screws for each arm.
7. Install the servo of the head between the two