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Bluetooth Controlled Robotic arm

Created by: arnav.upadhyay40
1 devlog
1h 10m 32s

A wireless 4-DOF robotic arm built with Arduino Nano, HC-05 Bluetooth module, and four MG90S servo motors. Controlled via a smartphone app over Bluetooth serial. Features custom ASCII packet parsing and smooth incremental servo motion (1°/10ms). I…

A wireless 4-DOF robotic arm built with Arduino Nano, HC-05 Bluetooth module, and four MG90S servo motors. Controlled via a smartphone app over Bluetooth serial. Features custom ASCII packet parsing and smooth incremental servo motion (1°/10ms). Includes full circuit schematic and Arduino sketch. Open-source hardware project.

This project uses AI

Used Claude in Readme.md (around 30%)

Demo Repository

README

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arnav.upadhyay40
arnav.upadhyay40 shipped Bluetooth Controlled Robotic arm
1 day ago

Shipped this project!

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The most significant challenge was building the serial parsing logic robustly. Incoming data arrives as a raw ASCII string, so digits had to be converted manually by subtracting 0x30, while comma separators had to be detected without being converted — requiring careful two-counter indexing to avoid off-by-one errors or buffer overflows. Power instability was another real hurdle: running four MG90S servos simultaneously caused voltage dips that would reset the Arduino. Adding the 1000 µF bulk capacitor and introducing the stepped 10 ms refresh cycle resolved this by distributing the effective load. Finally, calibrating servo direction took physical trial and error — the base and gripper are mounted in orientations that invert their motion relative to the app’s slider, which is why the firmware applies a 180 - angle transform specifically for those two joints.

arnav.upadhyay40
arnav.upadhyay40 worked on Bluetooth Controlled Robotic arm
1 day ago
1h 10m logged

Working on this project provided hands-on experience across several domains. On the hardware side, I learned how to correctly wire multiple servo motors to a shared 5V rail and how the 1000 µF decoupling capacitor is critical for preventing voltage brownouts when servos draw surge current simultaneously. I gained a solid understanding of how the HC-05 module bridges Bluetooth SPP communication to the Arduino’s UART, and why TX/RX lines must be disconnected during firmware upload. On the firmware side, I developed a deeper appreciation for custom serial protocol parsing — handling raw byte streams character by character, stripping ASCII offsets, and using delimiter/terminator bytes to frame multi-value packets. I also learned the value of smooth motion control: stepping the servo 1 degree every 10 ms dramatically reduces mechanical stress and produces far more natural movement than jumping directly to a target angle.

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