Introduction: PROJECT: Impulse

A third hand

Step 1: Tools and Parts List


  • 3D Printer (Lulzbot Mini and TAZ6)
  • Drill
  • Sandpaper
  • Super Glue
  • 3D Modeling Software (Autodesk Fusion 360)


Step 2: 3D Model

We used one of our teammate's hands as a reference model by taking the measurements of each finger segment as you can see in the picture above. Using the dimensions we measured, we were able CAD each finger and the palm.

After testing if each finger slides perfectly into the palm, we made holes in the palm to route the wires down to the forearm. The forearm was designed to slot into the palm perfectly. We also added humps on the forearm to offset the servos so that the nylon wires do not interfere with each other.

Step 3: Print

We used a Lulzbot Taz with the settings above to print out all the finger parts, palm, and forearm.

Step 4: Assemble

Sand the flat parts of each finger part and make holes larger if necessary. Then use superglue to put the segments together and use the M3 screws as joints for the segments. After doing this for every finger, slide the joints into the palm. To attach the forearm to the palm, we sandwiched the palm between two parts that make up the forearm. In order to have the flex sensors read the movement of your fingers, we glued them to the glove that the user would wear. After this, we attached the extension wires to the pins of the flex sensors by smoldering them to the pins. Finally, we used an Arduino Mega where we coded the hand to match the user's movements within the glove.

Step 5: Code

The code first defines where each servo and flex sensor is attached. Then it starts calibration mode which takes the minimum and maximum values from the flex sensors and maps them to the minimum and maximum values on the servo. The last part of the code tells the servo to move to a position based on the input value from the sensor.

Step 6: Final Test