Introduction to the Robotic Hand Project
Building a gesture-controlled robotic hand is one of the most exciting and impressive projects you can undertake in electronics. Whether it is for a B.Tech major project, a prosthesis prototype, or just for fun, this tutorial will teach you how to map the movements of your own hand to a 3D-printed robotic hand using an Arduino and flexible bend sensors.
Components Needed
To follow along with this tutorial, you will need a few core components. You can grab all of these directly from our trusted hardware partner, KSP Electronics, with fast shipping across India!
- Spectra Symbol Flex Sensors (80mm) (You need 5 of these, one for each finger)
- Arduino UNO R3 (DIP Version)
- MG996R or SG90 Servo Motors (5 pieces)
- PLA PRO+ Daisy White Filament (For 3D printing the hand structure)
- Jumper Wires Combo and a Breadboard
- Fishing line or strong nylon thread (acting as tendons)
Step 1: 3D Printing the Hand
First, you need the mechanical structure. We highly recommend using the open-source InMoov robotic hand files found on Thingiverse. Print the palm, fingers, and servo bed using a strong material. Our absolute favorite is the Daisy White PLA PRO+ because it prints fast and leaves a flawless, clean finish that mimics bone structure beautifully.
Step 2: Understanding the Spectra Symbol Flex Sensor
The magic of this project lies in the Spectra Symbol Flex Sensor. This is a variable resistor. When it lays flat, its resistance is around 10K ohms. As you bend it, the resistance increases up to 30K or 40K ohms. By creating a voltage divider circuit with a static 10K resistor, the Arduino can read this bending motion as an analog voltage (0 to 1023).
Step 3: The Circuit
Connect each Flex Sensor to an Analog Pin (A0 to A4) on the Arduino UNO. Make sure to use a 10K pull-down resistor for each sensor. Connect your 5 servo motors to the digital PWM pins (Pins 3, 5, 6, 9, 10). Note: Do not power 5 servos directly from the Arduino 5V pin! Use an external power supply like an 18650 battery pack for the servos, ensuring you share the common GND with the Arduino.
Step 4: The Arduino Code
Here is a basic snippet to map the flex sensor to a servo motor. You will replicate this for all 5 fingers.
#include <Servo.h>
Servo thumb;
int flexPin = A0;
void setup() {
Serial.begin(9600);
thumb.attach(3);
}
void loop() {
int flexValue = analogRead(flexPin);
// Map the analog value to a servo angle (0 to 180)
int servoPos = map(flexValue, 700, 900, 0, 180);
// Constrain to prevent servo jitter
servoPos = constrain(servoPos, 0, 180);
thumb.write(servoPos);
delay(20);
}Conclusion
Once you sew the sensors into a glove, every time you bend your finger, the Arduino reads the resistance change and pulls the corresponding servo motor, clenching the robotic fist! This is a fantastic introduction to biomechatronics. Make sure to source high-quality Flex Sensors from KSP Electronics, as cheap clones often break after just a few bends.
