Building EMG Prosthetics: Arduino & 3D Print

Learning Goal: Design and prototype a low-cost, EMG-controlled prosthetic hand utilizing myoelectric sensors, an Arduino, and 3D-printed tendon-driven mechanical linkages.

Prerequisites

• Basic computer literacy (downloading and installing software).
• Access to a 3D printer (or a 3D printing service) and PLA filament.
• Basic electronics toolkit (breadboard, jumper wires, soldering iron is helpful but optional).
• No prior coding experience is required; we will build your programming foundation from scratch.

Estimated Study Time

• Total Estimated Hours: 28 hours (includes video instruction, hands-on physical prototyping, software debugging, and calibration exercises).

Module 1: Intro to Myoelectric Signals & Muscle Anatomy

In this module, you will explore how muscle contractions generate electrical signals (EMG) and learn the physiological basis of myoelectric control. Understanding how action potentials propagate across muscle tissue is critical for choosing optimal electrode placement on the forearm to capture clean, reliable signals for your bionic hand.

Recommended Videos

Introduction to Electromyography (EMG)

@NatalyMedina-ICE10:003777

Introduction to Electromyography (EMG)

Electromyography (EMG) is a biomedical technique that detects, analyzes, and utilizes electrical signals (myoelectric signals) produced by muscle activation through ion exchange across muscle membranes; these signals are captured using electrodes and processed through differential amplification, filtering (typically 50-150 Hz), and analog-to-digital conversion for clinical diagnosis of neuromuscular disorders like ALS and muscular dystrophy, as well as for controlling robotic prostheses, though

@NatalyMedina-ICE · 10:00

• Why this video: This video introduces the biological basis of myoelectric signals. It explains how ion exchanges across muscle membranes generate detectable surface potentials. This scientific groundwork is vital to understand what your sensors are actually capturing.
• Knowledge Checkpoint:
  • Explain how muscle fibers produce biopotentials during a contraction.
  • Distinguish between surface electromyography (sEMG) and needle EMG.
  • Define the amplitude and frequency ranges typical of surface EMG signals.

Electromyography (EMG) Basics, Muscle Hypertrophy, Denervation, Rigor Mortis - Muscle Physiology

@MedicosisPerfectionalis14:55195159

Electromyography (EMG) Basics, Muscle Hypertrophy, Denervation, Rigor Mortis - Muscle Physiology

Electromyography (EMG) records the electrical activity of muscles and their supplying motor neurons, using cathode ray oscilloscopes instead of metal needles to detect millivolt fluctuations. In neurogenic disease, denervation causes compensatory hypertrophy of surviving motor units, resulting in increased amplitude during weak contractions and fasciculations/fibrillations; in myopathy, motor units shrink, decreasing amplitude and duration. Muscle hypertrophy refers to increased muscle fiber siz

@MedicosisPerfectionalis · 14:55

• Why this video: This video provides clinical and anatomical depth regarding how motor neurons stimulate motor units. It bridges the gap between neural commands and actual mechanical muscle twitching, helping you strategically decide where to place skin electrodes over target muscle bellies.
• Knowledge Checkpoint:
  • Define a "motor unit" and describe its role in EMG signal generation.
  • Describe the phase relationship between motor unit action potentials (MUAPs).
  • Identify which forearm muscles (e.g., flexor carpi radialis) are activated when making a fist gesture.

The surprising reason our muscles get tired - Christian Moro

@TEDEd00:285719765

The surprising reason our muscles get tired - Christian Moro

When the brain sends a signal, motor neurons release acetylcholine, which triggers pores on the muscle cell membrane to open. Sodium ions flow into the cell while potassium ions flow out. This flux of charged particles creates an electrical signal called an action potential that spreads through the muscle cell, stimulating the release of stored calcium.

@TEDEd · 00:28

• Why this video: Although brief, this animated lesson visualizes the cellular action potential—explaining how sodium-potassium pumps open and trigger voltage shifts. This structural perspective allows you to visualize the micro-currents that your MyoWare sensor will amplify.
• Knowledge Checkpoint:
  • Diagram how sodium and potassium ions flow across muscle cell membranes to trigger contractions.
  • Explain how a loss of ionic balance affects the amplitude of myoelectric output during muscle fatigue.

Module 2: 3D Printing & Tendon-Driven Mechanical Design

In this module, you will study the mechanical architecture of 3D-printed bionic hands. Rather than using rigid metal gears, low-cost prosthetics utilize "tendon-driven underactuated mechanical linkages." You will study structural configurations, support material removal, and the mechanical physics of underactuated grasping.

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e-NABLE Talon Hand 2.0 - Tutorial Part 1

@eNABLEVolunteerCommunity41:2511606

e-NABLE Talon Hand 2.0 - Tutorial Part 1

This tutorial demonstrates the complete process of preparing and assembling 3D printed prosthetic hand parts, including removing support material using various tools (fingernails, files, pocket knives, pliers), filing and sanding surfaces for smooth motion, installing snap pins and cables, and attaching elastic tensioners to enable natural finger movement.

@eNABLEVolunteerCommunity · 41:25

• Why this video: A comprehensive, hands-on tutorial on processing 3D-printed prosthetic components. It teaches crucial techniques for cleaning print imperfections, clearing out internal tendon channels, and prepping polymer knuckles for assembly.
• Knowledge Checkpoint:
  • Identify the safety precautions and tools needed for post-processing 3D-printed parts (e.g., reaming holes, removing support structures).
  • Explain why clearing out internal channels is vital for low-friction tendon movement.
  • Describe how layer-line orientation in FDM 3D printing affects structural stress limits in finger segments.

How to Build Your Own Biomimetic Bionic Hand

@WillCogley15:00203647

How to Build Your Own Biomimetic Bionic Hand

This video demonstrates how to construct a biomimetic bionic hand using 3D-printed components, modified servo motors, and custom electronics. The key mechanical principles include: (1) modifying standard servos (like DS939 MG) for continuous rotation by removing internal gears and potentiometer limitations; (2) creating tendon-driven finger movement using fishing line cables routed through 3D-printed pulleys; (3) assembling a modular forearm and wrist structure with multiple servos; (4) integrat

@WillCogley · 15:00

• Why this video: An elite showcase of building a highly articulated 3D-printed hand. This video breaks down the mechanical kinematics of modifying standard servos, routing lines, and using flexible joints as structural restoration springs.
• Knowledge Checkpoint:
  • Distinguish between biological joints (IP, MCP, CMC) and their mechanical equivalents in a prosthetic hand.
  • Explain how elastic joints function as a passive extension mechanism to open the fingers when the pull-tendon relaxes.

Lecture 1 \| MIT 6.832 Underactuated Robotics, Spring 2009

@mitocw01:14:11166257

Lecture 1 \| MIT 6.832 Underactuated Robotics, Spring 2009

An underactuated system is a mechanical system where the control input cannot accelerate the system in every direction, meaning the rank of the input matrix F2(q, q̇, t) is less than the dimension of the state vector q; this concept is crucial in robotics because most interesting problems—walking, flying, and manipulation—are inherently underactuated, requiring control strategies that exploit the system's natural dynamics rather than simply overriding them with high-gain feedback.

@mitocw · 01:14:11

• Why this video: A high-level theoretical masterclass on underactuated systems. You will learn the mechanical physics of having fewer control inputs (actuators/servos) than degrees of freedom, which is the foundational design pattern of adaptive, conformable robotic grips.
• Knowledge Checkpoint:
  • Define what makes a mechanical system "underactuated."
  • Explain why underactuation is an advantage when grasping irregular three-dimensional objects.

Module 3: Arduino & EMG Sensor Hardware Foundations

Here, you transition to physical electronics. You will learn to safely set up your microcontroller, power your circuit safely, interface the analog pins of an Arduino Uno, and hook up a professional-grade muscle sensor (like the MyoWare) without creating ground loops or short circuits.

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Tutorial 01 for Arduino: Getting Acquainted with Arduino

@sciguy1412:242614181

Tutorial 01 for Arduino: Getting Acquainted with Arduino

Arduino is an open-source hardware prototyping platform based on Atmel ATmega microcontrollers, designed for electronics projects and automation. This tutorial covers the complete Arduino setup process: hardware components needed (Arduino board, USB cable, power supply, breadboard, LEDs, resistors, motors, sensors), software installation from arduino.cc, and the Arduino IDE environment. The core programming concepts include the sketch structure with void setup() for initialization and void loop(

@sciguy14 · 12:24

• Why this video: The ultimate introductory guide for microcontrollers. This video walks through installing the Arduino IDE, connecting your board, and running your first upload, ensuring your local development workspace is fully validated.
• Knowledge Checkpoint:
  • Identify key hardware features of an Arduino Uno (e.g., ATmega328P, digital pins, analog pins, power pins).
  • Successfully write, compile, and upload a basic sketch using the Arduino IDE.
  • Differentiate between digital inputs (HIGH/LOW) and analog inputs (0 to 1023 resolution).

DIY Electromyography using MyoWare EMG Muscle Sensor & Arduino

@HowtoElectronics10:2080066

DIY Electromyography using MyoWare EMG Muscle Sensor & Arduino

Electromyography (EMG) is a technique for measuring electrical activity in skeletal muscles during contraction; this video demonstrates how to create a DIY EMG device by interfacing the MyoWare Muscle Sensor with Arduino, which detects the electrical signals generated by muscle fibers when they contract and converts them into measurable voltage outputs that can be displayed as waveforms or numeric values.

@HowtoElectronics · 10:20

• Why this video: An incredibly direct tutorial demonstrating how to wire the popular MyoWare muscle sensor to an Arduino's analog input pin, place sEMG pads on skin surfaces, and plot the voltage output.
• Knowledge Checkpoint:
  • Diagram the three core electrode connections: reference, end-muscle (muscle belly), and mid-muscle.
  • Explain how to power the MyoWare sensor safely to prevent electrical shock and reduce 50/60 Hz mains power noise.
  • Open the Arduino Serial Plotter to visualize changes in sEMG amplitude during muscular contraction.

EMG Muscle Sensor Module with Arduino

@SaravananAL06:43129359

EMG Muscle Sensor Module with Arduino

An EMG (Electromyogram) sensor measures muscle electrical activity through surface electrodes, producing a signal that indicates muscle contraction or relaxation; this module requires a dual power source of +9V and -9V connected to an Arduino board, where the signal pin connects to analog input A0, allowing real-time monitoring of muscle activity through serial plotter and enabling applications in medical equipment, robotics, and gaming through signal mapping to control external devices like ser

@SaravananAL · 06:43

• Why this video: A deeper hardware explainer demonstrating alternative raw EMG boards that require dual-rail power supplies (+9V, -9V, and Ground). It details how operational amplifiers (Op-Amps) and differential amplifiers reject common mode noise.
• Knowledge Checkpoint:
  • Explain the concept of "Common Mode Rejection Ratio" (CMRR) in bio-amplifiers.
  • Create a dual-battery power supply routing to achieve positive and negative voltage rails for analog conditioning circuits.

Module 4: Arduino Coding: Servos, EMG Thresholding, and Noise Filtering

This module focuses on software engineering. You will program your Arduino to read raw analog data, smooth out raw high-frequency fluctuations, establish dynamic activation thresholds, and translate muscle signals into smooth servo movements.

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Electronic Basics #25: Servos and how to use them

@greatscottlab00:41976965

Electronic Basics #25: Servos and how to use them

To control a servo using an Arduino, connect the servo to a separate power supply and use pin 9 along with the Arduino Servo library. The library generates the required PWM signal automatically. By varying the input signal between 0.5 milliseconds to 2.5 milliseconds, the servo can achieve its full 180° rotation range.

@greatscottlab · 00:41

• Why this video: Clarifies how hobby-grade servo motors use Pulse Width Modulation (PWM) signals to control the internal potentiometer position loop. Essential for understanding how we command the physical tendon tensioners.
• Knowledge Checkpoint:
  • Describe the standard PWM signal duty cycle needed to move a hobby servo from 0 to 180 degrees.
  • Write basic code utilizing the official Arduino <Servo.h> library.
  • Explain why powering a servo directly from the Arduino's 5V rail can cause system resets or brownouts.

MyoWare Servo Tutorial - EMG Arduino Circuit

@Frank-yb4zd07:0163946

MyoWare Servo Tutorial - EMG Arduino Circuit

This tutorial demonstrates how to control a servo motor using the MyoWare muscle sensor by Advancer Technologies, which reads muscle signals from the bicep and translates them into servo movements through an Arduino UNO board. The circuit connects the MyoWare sensor to the Arduino's 3.3V output, ground, and A3 analog input, while the servo connects to pin 9, 5V, and ground. The Arduino program reads muscle activation values from A3 and moves the servo to different positions based on a threshold

@Frank-yb4zd · 07:01

• Why this video: Directly integrates the concepts of reading muscle sensor voltage levels and transforming those raw variables into servo motor rotation commands.
• Knowledge Checkpoint:
  • Implement a conditional control loop (if-else statement) to trigger servo movement when EMG levels cross a static limit.
  • Use the Arduino map() function to proportionally control the servo angle based on muscle contraction intensity.

How to design and implement a digital low-pass filter on an Arduino

@curiores11103:27188169

How to design and implement a digital low-pass filter on an Arduino

This section introduces Butterworth filters as a solution to the transition band limitations of first-order filters. The Butterworth filter offers greater attenuation and progressively narrower transition bands with increasing order, approaching the ideal filter response. The mathematical formulation uses a polynomial in the denominator of order n, with coefficients following a specific recursion formula established by Stephen Butterworth in 1930. The first coefficient is always set to 1, and su

@curiores111 · 03:27

• Why this video: Introduces the math and code structures required to program a digital filter. Because EMG signals are inherently noisy, software low-pass filters prevent your servo motors from jittering randomly.
• Knowledge Checkpoint:
  • Explain why raw ADC data requires digital smoothing in real-time embedded systems.
  • Implement a first-order low-pass recursive formula in C++: $y[n] = \alpha \cdot x[n] + (1 - \alpha) \cdot y[n-1]$.

Tutorial 11 for Arduino: SD Cards and Datalogging

@sciguy1401:00340561

Tutorial 11 for Arduino: SD Cards and Datalogging

Raw sensor data often contains noise and anomalies that obscure meaningful trends. Applying a moving average filter smooths the data by averaging each point with neighboring points. In Excel, add a trendline with moving average option and adjust the period (number of points to average) to filter out noise while preserving the underlying trend. Periods around 10 often work well for smoothing sensor data.

@sciguy14 · 01:00

• Why this video: While centered on datalogging, this segment introduces the algorithmic implementation of a "moving average filter" using circular buffers.
• Knowledge Checkpoint:
  • Write a custom Arduino loop that continuously averages the last 10 raw analog readings to eliminate transient voltage spikes.

💡 Supplemental Coding Guide: EMG Threshold Calibration & Noise Filter

To address the common gap of writing clean signal processing algorithms, study and write this template code into your Arduino IDE. It sets up a rolling moving average filter and dynamic calibration process:

#include <Servo.h>

Servo tendonServo;

const int emgPin = A0; // Muscle sensor analog pin const int numReadings = 15; // Size of the smoothing window int readings[numReadings]; // Array for moving average int readIndex = 0; // Current index in array long total = 0; // Running sum int smoothedEMG = 0; // Filtered output value

int thresholdMin = 150; // Calibrated baseline rest value int thresholdMax = 600; // Calibrated max contraction value

void setup() { Serial.begin(9600); tendonServo.attach(9); // Connect servo PWM to digital pin 9

// Initialize all readings to zero for (int thisReading = 0; thisReading < numReadings; thisReading++) { readings[thisReading] = 0; }

// Perform dynamic calibration on boot (5 seconds) Serial.println("Relax muscles. Calibrating baseline rest..."); delay(1500); int baselineSum = 0; for(int i=0; i<100; i++){ baselineSum += analogRead(emgPin); delay(10); } thresholdMin = (baselineSum / 100) + 30; // set baseline slightly above average rest Serial.print("Baseline Min Set to: "); Serial.println(thresholdMin); }

void loop() { // 1. Calculate Moving Average to filter out high-frequency noise total = total - readings[readIndex]; readings[readIndex] = analogRead(emgPin); total = total + readings[readIndex]; readIndex = readIndex + 1;

if (readIndex >= numReadings) { readIndex = 0; }

smoothedEMG = total / numReadings;

// 2. Map filtered signal to servo rotation output (0-180 degrees) int servoAngle = map(smoothedEMG, thresholdMin, thresholdMax, 0, 180); servoAngle = constradictValue(servoAngle, 0, 180); // clamp bounds

tendonServo.write(servoAngle);

// Debugging output for visual plotting Serial.print("Raw_EMG:"); Serial.print(analogRead(emgPin)); Serial.print(","); Serial.print("Filtered_EMG:"); Serial.print(smoothedEMG); Serial.print(","); Serial.print("Servo_Angle:"); Serial.println(servoAngle);

delay(15); // standard control loop pacing }

int constradictValue(int val, int minVal, int maxVal) { if (val < minVal) return minVal; if (val > maxVal) return maxVal; return val; }

Module 5: Prosthetic System Assembly, Calibration & Testing

In this final module, you will physically compile all previous steps into a unified system. You will assemble your 3D-printed segments, route physical tendon lines, connect passive return springs, mount your servo motor horns, and execute a clinical calibration loop.

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3 Stringing Hand \| Kwawu 3.0 Prosthetic Arm Assembly Instructions

@JacquinBuchanan08:012290

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When stringing a prosthetic hand, pull the string through the Whipple tree and tie it off at the finger ends while holding the fingers in their maximum open position, ensuring the string is pulled as tight as possible to achieve even tension across all fingers and create a flat, functional hand.

@JacquinBuchanan · 08:01

• Why this video: An exceptional procedural guide showcasing exactly how to thread, pull, tension, and secure high-strength dacron or monofilament lines through a 3D-printed prosthetic forearm structure.
• Knowledge Checkpoint:
  • Describe how to lock the finger joints in a "fully open" baseline position during tendon tensioning.
  • Identify optimal knots (such as bowlines or tensioner knots) to prevent tendon slippage under high tensile load.

How to Make an Iron Man Suit \| 3D Printed MK85 Cosplay - Part 2

@FranklyBuilt01:0172294

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For attaching finger segments in 3D printed hands, cut thin strands of stretchy elastic bands (available cheaply on Amazon or eBay) and glue them along the back of each finger joint using super glue. The elastic provides tension that keeps fingers in their natural position while allowing full range of motion. This method creates a comfortable, flexible connection that mimics natural hand movement.

@FranklyBuilt · 01:01

• Why this video: Demonstrates the highly practical method of attaching thin elastic bands along the dorsal side of 3D-printed finger segments to act as a physical joint return spring.
• Knowledge Checkpoint:
  • Explain why a reliable elastic joint-return mechanism is needed in single-tendon underactuated systems.
  • Select appropriate elastic materials (e.g., elastic sewing cords, silicone bands) and bond them securely to PLA surfaces using CA glue.

Star Wars BB-8 Droid v3 #5 \| Head Control Arm \| James Bruton

@jamesbruton01:0775465

Star Wars BB-8 Droid v3 #5 \| Head Control Arm \| James Bruton

The servos use standard nylon servo horns, which are tough and durable. A camera-shaped piece is printed to attach to the servo horn, with a hole in the end that allows the studing to rotate fully. The studing is screwed into the gimbal assembly, and nuts and washers are used to tighten the grip and provide proper spacing between bearings to prevent magnets from pulling against the motor.

@jamesbruton · 01:07

• Why this video: Demonstrates practical mechanical linkages using standard nylon servo horns. It showcases how to attach structural wire or high-tension lines directly to rotating servo horns without stripping the delicate plastic output gears.
• Knowledge Checkpoint:
  • Safely drill out holes on a nylon servo horn to match tendon diameters without weakening the structural integrity of the horn.
  • Calculate the linear travel range of a tendon based on the radius of your mounting servo horn ($C = 2 \pi r \cdot \frac{\theta}{360}$).

⚙️ Step-by-Step System Assembly & Tensioning Guide

Because full system integration has historically limited video coverage, follow this step-by-step engineering SOP to complete your build:

1. Clean print channels: Take a $1.5\text{ mm}$ steel rod or guitar string and push it through the routing channels inside each finger segment to clear out layer anomalies, printing dust, and loose supports.
2. Install the joint return cords: Cut strips of $1.5\text{ mm}$ elastic cord. Glue the elastic cord along the back knuckles (dorsal side) of each finger using cyanoacrylate (super glue) and accelerator. When you fold a finger manually, the elastic cord should stretch and immediately pop the finger back open when released.
3. Route the main pull-tendon: Securely tie a heavy knot at the distal fingertip print cavity using a non-stretch $50\text{ lb}$ braided Dacron fishing line. Route the string down through the internal pathways of each joint, emerging at the base of the wrist.
4. Mount the servo motors: Zero out your servo motors by uploading a temporary script driving them to $0^\circ$. Install the custom 3D-printed tension brackets or nylon servo horns onto the splined output shaft.
5. Attach and tension the lines: Ensure the hand is fully extended by the elastic bands. Pull the tendon lines taut until there is zero slack in the fingers. Tie off the lines to the furthest hole of your servo horn, and lock the knot using a drop of nail polish or super glue to prevent fraying.
6. Integrate and Calibrate: Connect your MyoWare muscle sensor electrodes to your dominant arm, power up the Arduino with an external 6V power source (for the servo), and adjust your thresholdMax value to match your individual muscle contraction envelope.

Course Map

This map outlines the recommended sequential pathway through the curriculum modules.

Key People Index

• Paul McWhorter (@paulmcwhorter): Renowned systems engineer and electronics educator. His direct, zero-jargon programming tutorials provide the absolute reference path for physical computer-science basics.
• Will Cogley (@WillCogley): An open-source mechanical designer specializing in complex, low-cost biomimetic bionic hands and mechanical tendon linkages.
• Dr. Russ Tedrake (MIT): Pioneer of underactuated control systems and robotic locomotion theory at the MIT Dynamic Design Lab.
• James Bruton (@jamesbruton): Former toy designer and legendary robotics builder known for showing highly intuitive, low-cost mechanics for tendon linkages and servo attachments.

Final Self-Assessment

Complete this comprehensive checkpoint to verify your engineering and soft-skills competence:

• Explain how muscle contractions translate to millivolt potentials detectable on the skin.
• Determine optimal electrode placement over muscle bellies versus non-conductive bony regions.
• Correctly adjust slicing parameters (such as wall count and infill density) to print durable structural hand pieces.
• Post-process internal printed tendon paths to minimize mechanical friction.
• Wire an analog EMG sensor without creating a hazardous ground loop or brownout condition.
• Program a working moving average digital filter to clean high-frequency sensor noise.
• Implement calibration variables within your code to customize the activation envelope of your prosthetic hand.
• Rig a tendon line using monofilament/braided Dacron line with proper tension locking knots.
• Build a robust passive elastic joint return mechanism.
• Demonstrate a complete myoelectrically-controlled physical grip cycle (fist contraction maps directly to prosthetic grip close).