Robotic Arm — Arduino + RAMPS 1.4

A 4-DOF belt-driven robotic arm running on an Arduino Mega 2560 + RAMPS 1.4 shield, with three NEMA17 + A4988 joints and a 28BYJ-48 (or servo) gripper. The shoulder uses a parallel linkage, so the heavy motors stay at the base and the printed parts don't have to carry them.

📺 It in motion: https://youtu.be/T5URUtJ1Zg4

Mechanical build, BOM, printable parts and step-by-step assembly live with the project on Printables / the maker portal. This repo is just the firmware.

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What's in here

robotArm_v0.81/
├── robotArm_v0.81.ino     ← main sketch (open this in the Arduino IDE)
├── config.h               ← board + feature selection (gripper, controller, axes)
├── pinout/
│   ├── pinout.h           ← default pin map (Arduino Mega + RAMPS 1.4)
│   ├── pinout_uno.h       ← Uno variant
│   └── pinout_wemosD1R32.h← Wemos D1 R32 / ESP32 variant
├── config_esp32.h         ← ESP32 build overrides
├── RampsStepper.{h,cpp}   ← stepper wrapper for A4988 on RAMPS
├── endstop.{h,cpp}        ← homing
├── byj_gripper.{h,cpp}    ← 28BYJ-48 + ULN2003 gripper driver
├── servo_gripper.{h,cpp}  ← alternative hobby-servo gripper
├── controller_ps4.{h,cpp} ← optional PS4 manual controller
├── controller_wiimote.{h,cpp} ← optional Wiimote manual controller
├── command.{h,cpp}        ← serial command parser
├── queue.h                ← move queue
├── interpolation.{h,cpp}  ← linear interpolation between target poses
├── robotGeometry.{h,cpp}  ← inverse kinematics for this arm
├── fanControl.{h,cpp}     ← 12 V cooling fan
└── logger.{h,cpp}         ← serial logger

config.h_samples/           ← reference configs (incl. upstream ftobler config)

Hardware target

Part	Default
MCU	Arduino Mega 2560
Driver shield	RAMPS 1.4
Joint motors	3× NEMA17 + A4988 (X / Y / Z = base / shoulder / elbow)
Gripper	28BYJ-48 + ULN2003 (default) — or hobby servo, see config.h
Homing	3× limit switches (one per stepper joint)
PSU	12 V / 4 A via 2.1 mm DC jack
Cooling	12 V 5010 fan

The Uno and ESP32 (Wemos D1 R32) pinouts are checked-in but the Mega + RAMPS combination is the supported reference build.

Pin assignments

Authoritative pin map: robotArm_v0.81/pinout/pinout.h for Mega/RAMPS, and pinout_uno.h / pinout_wemosD1R32.h for the alternative boards.

TODO (maintainer): hoist the X/Y/Z/E step+dir+enable pins, the three endstop pins, the gripper pins and the fan pin into a table here so visitors don't have to open the header.

Build & flash

Arduino IDE

1. Install the Arduino IDE 1.8.x or 2.x.
2. Tools → Board → Arduino Mega 2560.
3. Open robotArm_v0.81/robotArm_v0.81.ino.
4. Install the libraries the sketch #includes through Tools → Manage Libraries…
   • TODO (maintainer): list the exact libraries here once verified against the #include lines in the .ino — likely candidates given the file layout: AccelStepper, Servo, and (only if you enable that controller) PS4Controller / a Wiichuck library. Do not install controller libs you don't use.
5. Connect the Mega over USB, pick the right port, and Upload.

Configuring before you flash

Open robotArm_v0.81/config.h and pick:

• Board / pinout — uncomment the matching pinout include
• Gripper — 28BYJ-48 stepper or hobby servo (mutually exclusive)
• Manual controller — none / PS4 / Wiimote (optional; the arm also works headless over serial)
• Axis direction flips and steps-per-degree — match these to your microstepping jumpers on the RAMPS board

The config.h_samples/ folder has reference configs you can diff against if your build behaves oddly.

Running it

After flashing, open the Serial Monitor at the baud rate set in the sketch (TODO: confirm — Serial.begin(...) in robotArm_v0.81.ino).

The firmware accepts a queued command stream parsed by command.cpp — see that file for the exact syntax it understands. The queue.h + interpolation.cpp pair suggests G-code-style buffered moves with linear interpolation between targets, but please confirm against command.cpp before relying on specifics.

If you wired up a PS4 pad or a Wiimote and enabled it in config.h, the arm can also be jogged manually — pairing instructions live in the relevant controller_*.cpp.

Homing

On startup the firmware drives each motorised joint toward its limit switch. Make sure all three switches are wired and triggering before you power up — an un-homed axis with a missing endstop will crash into the frame.

Troubleshooting

• Sketch won't compile, complaining about a missing library — check the #include lines at the top of robotArm_v0.81.ino and the controller_*.h files; install whatever's missing through the Library Manager.
• Steppers buzz but don't turn — A4988 Vref not set, or microstepping jumpers under the drivers don't match config.h. Set Vref to ~0.7 V for a NEMA17 first, then tune.
• Joint runs the wrong way — flip its INVERT_* flag in config.h (or swap one coil pair on the motor connector).
• Endstop never triggers / triggers permanently — RAMPS endstop headers are 3-pin (S / – / +); a swapped connector latches the input. Test with a multimeter in continuity mode.
• Gripper stepper just hums — 28BYJ-48 coil order on the ULN2003 is IN1-IN2-IN3-IN4; getting the order wrong gives vibration without rotation.

Credits

This codebase shares structure with ftobler/robotArm (see config.h_samples/config_sample_V0.61/ftobler_original/). If this repo is derived from that project, the upstream license applies — TODO (maintainer): confirm the lineage and add a proper attribution + matching LICENSE file.

License

TODO (maintainer): commit a LICENSE file. If this is derived from ftobler/robotArm it inherits GPL-2.0; if it's an independent rewrite, pick one (MIT / GPL-3.0 / CC-BY-NC-SA for the docs, etc.) and reference it here.