RA01 · 4-axis desktop robotic arm
A real 4-axis robotic arm your students build with a screwdriver, drive with two joysticks, and program in the browser.
4 axes ~160 mm reach 9 V 1 A USB
Inside the machine
4
axes of motion
160 mm
working reach
10
hands-on labs
13
weeks of curriculum
Every plate laser-cut and numbered, every servo labeled, every screw accounted for. Students build it in one session with the included screwdriver. No soldering.
Color
Ships in black, with three more colors for class-set orders.
Two thumb joysticks sit right on the controller board, so the arm works before anyone writes a line of code. When the class is ready, the same board reflashes from the browser. The joystick program is just the first firmware it runs.
servo pins 9 / 8 / 7 / 6 9 V 1 A center-positive USB CH340
The upper arm is a parallelogram linkage, the same mechanism a desk lamp uses. It keeps the gripper pointing the same way as the arm extends, so there is no wrist to solve.
That is the whole reason a Grade 9 student can write real inverse kinematics for this arm. Six axes needs matrices. Four axes with a fixed wrist needs atan2 and the law of cosines, trigonometry a student already has, doing an actual job.
The frame is laser-cut black acrylic with 80, 80 and 68 mm links. A cracked link is a small, cheap plate that swaps out in minutes, not a reason to retire the arm.
inverse_kinematics.cpp
// L1 = 80 mm, L2 = 80 mm, the two arm links
float d = sqrt(x*x + y*y);
float a1 = atan2(y, x);
float a2 = acos((L1*L1 + d*d - L2*L2)
/ (2 * L1 * d));Blocks on Monday. This, by June. Same arm, same browser.
No. The editor, the simulator, the compiler and the USB connection all run in the browser. That is deliberate: school IT departments do not have to approve anything, and it works on a managed Chromebook.
Yes, all of it. Every graded lab runs on a simulated ATmega328P in the browser, and Arm Studio has a Simulate mode that animates the arm from the same maths the real one uses. The hardware turns a passing program into a working machine. It is the reward, not the gate.
It is how most classes run it. Four students each write and grade their own programs in the simulator, then take turns proving them on the shared arm. Nobody waits for hardware to make progress.
No. It has four, and we would rather say so. An earlier version of this page claimed six, which was wrong. Four axes with a parallelogram linkage is the right amount of geometry for school: solvable with trigonometry a student already has, and still genuinely inverse kinematics.
No. Blocks are the on-ramp. One button turns any block program into the real Arduino C++ it represents, which the student can then edit, compile and flash. By module 4 most students have stopped using blocks entirely.
The browser standard for talking to USB devices (Web Serial) only exists in Chrome, Edge, Opera and ChromeOS. On Safari or an iPad everything works except driving a physical arm. Blocks, code, the simulator and the graded labs are all fine.
Black as standard; clear, blue and orange frames available for class sets.
| Axes | 4: base yaw, shoulder, elbow, gripper |
| Links | 80 / 80 / 68 mm, parallelogram four-bar keeps the gripper level |
| Working reach | ~160 mm |
| Frame | Laser-cut acrylic in black; blue, clear and orange available |
| Board | ATmega328P + CH340 USB-serial, dual-joystick shield |
| Servo pins | 9 / 8 / 7 / 6 |
| Power | 9 V 1 A DC, center-positive 5.5 × 2.1 mm, no lithium cells |
| Connectivity | USB; IR and Bluetooth (HC-06) supported, not included |
| Programming | Browser blocks, Arduino C++, or live serial commands |
| Browser support | Chrome, Edge, Opera, ChromeOS for USB control; any browser for the simulator |
| Safety | Grades 5-12 (about 10-18), adult supervision for assembly; contains small parts, not for children under 3 |
The arm, the browser studio, and a semester of curriculum. One box, one budget line.