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How to build a JRobot

Humanoid Bipedal 3D Printed Robot Kit

BUY JRobot

Before Assembly

There are many components to build the JRobot! Including Plastics, screws, servo motors and electronics parts.

Servo Motors

These are the most important parts. Servo Motors are used.

there are motors with different wire lengths.

  • A the short wires, use for the Body, and Legs (total 10 servo motors).
  • B the longer wires, use for Arms, the rotors of the motors are white in color (total 4 servo motors).
  • C the longest wires, use for Legs (total 4 servo motors)


Some tools we may use when build J-Robot.

from left to right, Screw Driver, Cutter

Tips There are 4 types of screw M (for motor), X, Y and Z
  • Screwdriver
  • All joints are done using screws. No glue is needed
  • Cutter
  • To remove the ears from the motors.
  • The cutting should be performing by instructors or by students under intensive guidance of instructors.

Kiddo Code

An App running on tablet computer to control robots

  • To adjust the default position.
  • To make poses.
  • Create action between poses.
  • Use Blockly coding to callout actions to play!


We will show you how to build the J-Robot step-by-step. Let’s start.

Body Core

Take the Body Core components and prepare 4 servo motors A

Body Core components

1. Put them inside the Body Core (two for the arms in left and right, two pointing downwards)

Put servo motors inside the Body Core

2. Insert the Central Partition

Insert the Central Partition

Body Back Parts

Body back and power switch

1. Attach the power switch to Body Back using screws Z x2

Put the power switch to Body Back

2. Body Back completed

Body Back completed


The Head components.

Upper head, Lower head, Eyes board and The hat (sometimes).

Notice The Head is quite difficult to build. The wire cable has to go through the neck.


1. Put on two screws X

The front looks like this

The Lower Head is assembled with the Eyes Boards.

2. The Wire cables go through the neck

3. Like this…

Now take out the Center Partitioner from the Body.

Notice Ask instructors or parents to help you.
4. Then make the wire cable goes through the Body.

5. Put on the screws Y onto the Lower Head and Body frame.

Again, diagonal screws first.

6. ….and four screws altogether.

7. Pull the wire cable until the board fits

8. At last, assemble the Head

The Head Completed

Body Core and Partition

1. Fix Body Partition: At last, we can fix the Body Partition using screws Y.

2. Put on 2 screws Y

3. Put on 2 screws Y

Body Front and Battery Pack

1. One wire goes from the upper side, the other from the lower side.

2. Put on the Chest. Hook onto the lower side first.

3. Apply screws X on the shoulders

4. ….both shoulders

Body Back and Electronic Board

1. Fix the Electronic Board to the Body.

Note that there are only 3 screws X

2. Now we connect the wires from motors to ESP board one by one.

IMPORTANT: All servo motors should be connected to the ESP board first.

Then switch on power to let them rotate to proper positions.

Then switch off and proceed to mechanical assembly.

Otherwise, the servo motors may burnt because of improper rotations.

Left Right
G14 — (not used) G16 — (not used)
G12 Shoulder G13 Shoulder
7 Hip 8 Hip
6 Arm 9 Arm
5 Hand 10 Hand
4 Upper Leg Sideway 11 Upper Leg Sideway
3 Upper Leg Front and Back 12 Upper Leg Front and Back
2 Knee 13 Knee
1 Lower Leg 14 Lower Leg
0 Foot 15 Foot

3. Right leg first

Note the BLACK wires are always on the outer side, white wires the inner side.

4. Right Arm

Note there is no wire connected to the FIRST slot!

5. Left Leg and Left Arm

6. The Eye Board from the Head

Note there is no wire connected to the FIRST slot!

7. The battery and the power switch

Right Leg

Upper Right Leg Upper Knee Lower Right Leg & Foot
Take the Right Leg components and prepare 5 servo motors; A x3 and C x2

Right Leg components

Upper Right Leg

Let’s try to build the Hip first

1. Apply first screw

In the photo, we use the flat screw X.

2. Apply diagonal screw

To apply screw correctly, make sure you do the diagonal screws first.

3. Apply other two

And then the other two.
Next layout the Upper Leg as shown.
The word “R1” should face outer sideways.
4. Prepare a servo motor A x1, put it in the Upper Leg housing.

After put servo motor in the Upper Leg housing.

5. Next put the Hip side arm with a Black Screw Z. Again, use the Servo Controller.

After put servo motor in the Upper Leg housing.

6. Connected Hip housing to the Body

Don’t forget to apply a Black Screw Z.

7. Apply other two

They will look like this

Right Knee

8. Knee Prepare another servo motor A and put it inside the Upper Leg housing pointing downwards.

It will fit

9. Connect the Knee side bar

Then connect the Knee side bar

10. Connect the join

11. Put on the Black Screw Z

12. Connect another join

13. Put on two Silver Screw Y

They will look like this

14. Put on the Knee servo motor A

Right Knee Completed

Right Lower Leg & Foot

Prepare the Lower Leg, Ankle and Foot parts

Note that there are 2 servo motors C with LONG wires for each of the Leg.

15. Put on the servo motors C

16. Use BLACK screw to tighten the foot sidebar. Z

17. Put on the Foot.

Make sure there is allowance space.

18. Tighten two screws X

Use screws that come with the motors.

19. Use BLACK screw Z to tighten the Lower Leg outer part to motor.

20. Connect with the Bar

21. Put on the screw X

22. Connect to the Knee motor with BLACK screw Z

23. Add the inner Lower Leg

24. Put on screw X

Right Leg Completed

Now the Right Leg should look like this

Left Leg

Refer to the method of Right Leg. Now build the Left Leg.

Take the Left Leg components and prepare 5 servo motors; A x3 and C x2

Left Leg components

The finished Legs should look like this.

Rear View
Front View


This is the layout of the Arms components. The shoulder core and side, the Arm itself and the hand.

Note the shoulder 4-screw mount is the same as the Hip.

Two servo motors B are needed for each Arm. Note that the rotors of the motors are white in color.

1. Put them in…

2. …and the other

The Hand

3. Assemble the Hand with the sidebar and the arm motor.

Note that there are two types of silver screws. SHORT M and LONG Y.

The SHORT one is for the motor, the LONG ones are for the plastic.

The Shoulder

4. Put the Shoulder Side Bar (marked with RH or LH) onto the Upper Arm motor.

See this movie of tuning. Make sure the normal position is correct and there is clearance.

Now, the Shoulder Core.

5. Put the Disc atop the Shoulder Core.

6. Put on the dedicated screws X.

Diagonal first

And then the other two screws, totalling 4 screws .

7. Again, use controller to tune the normal position.

See this movie of tuning.

8. At last, connect both shoulder parts together Y.

Don’t forget to tighten with screw and make sure the wires go through the joints correctly.


The Arm Completed

The same building method for the Left Arm

Back Cover

We are almost done. Make sure the motor “Home Positions” are tuned, otherwise, do not cover the electronic board! If in doubt, go back to here.

1. Prepare the Back Cover .

2. Right Arm wires and power switch go into this slot.

3. Left Arm wires

4. Wires of the Legs.

Note that no Cable Ties should be seen from outside.

5. Hook onto the lower side.

6. Apply 2 screws X onto shoulders.

7. Use Kiddo Code to try again.

Wi-Fi Configuration

After power on J-Robot, if its LED keeps flashing in GREEN color for more than 15s, its WiFi is probably not configured properly. Run the “Auto WiFi Config” option in Kiddo Code and then follow the on-screen instruction to configure J-Robot WiFi.

The requirement for J-Robot’s WiFi is as follows

  • 2.4 GHz WiFi, IEEE 802.11n protocol, WPA/WPA2 authentication
  • IPv4 network
  • Allow to access Multicast 234.x.x.x on port 7001, where x is 1 to 100
  • Allow to access UDP broadcast on IP address on port 6000

Make sure iPad is using same Wi-Fi that J-Robot is using.

Tune Home Position

Home position of J-Robot the should be tuned to stand up straight pose as indicated in the below diagrams.

After home position tuning is done, power off and on the J-Robot and wait until its LED change to green to check if home position is set properly.

Arms down

Hand/knee are aligned like this

3 screws on the line; around 95 degrees and robot learns to front a bit

Feet are parallel @ side

Feet are parallel @ front


Log into Kiddo Code, open J-Robot Chapter for tuning home positions..

After J-Robot runs motions for dozens of minutes, its home position may be drifted a bit. You may need to tune home positions from time to time.

  1. Tap the “Home” segmented control button
  2. Tag a joint number (1 ~ 18) on the J-Robot image
  3. Move the slider at the bottom to a value to set the joint to home position, or tap on the text field below the slider to input the new value directly

Caution: If setting a joint to an extreme value such that its servo cannot be rotated to the target angle, you will hear a hissing sound and the servo will be burnt easily, especially for the knee and hip joints. Therefore, when you hear a hissing sound, you must not let J-Robot to stay on this pose for long.
Press “JRobot” button

Tag “Joint Calibration”

Tag a joint number to calibrate.