InMoov Single FingerInMoov Single Finger

VIDEO AT BOTTOM OF POST

I’ve been following the InMoov project for a while, and was waiting for a good time to jump in and start working on one. When the Single Finger starter project was posted on Thingiverse, I decided that it was the perfect place to start.

This project requires:

  • Arduino Uno
  • 3D Printer
  • Servo Motor
  • Fishing Line
  • 2.8mm and 3.2mm drill bits
  • Dremel Tool for sanding
  • 3mm nuts and bolts
Printed PartsPrinted Parts

The first step is printing out the parts. I printed out the base and the finger joints at a .25mm layer height, but I printed out the gear that attaches to the servo at a .1mm layer height. This allows the gear to slip onto the teeth of the servo gear a little easier.

The Arduino and servo motor in placeThe Arduino and servo motor in place

When assembling the finger, the instructions on the InMoov blog call for a 3mm and a 3.5mm drill bit, which are difficult to find. Drill out the finger joints first with an easier to find 2.8mm bit, then switch to the 3.2mm bit to prevent the plastic from cracking or separating.

I used a Dremel tool to shave down a bit on the inside of the finger joints; this allows them to move in and out a little smoother. The finger should move freely before it is all hooked up, and should not have any catches or burrs in the joints preventing it from moving smoothly.

Rubber feet affixed to the bottomRubber feet affixed to the bottom

I added rubber feet to the bottom of the base to prevent it from sliding around while it is running.

Servo close-upServo close-up

I was unable to find the HobbyKing servo used in the original build, so I substituted a HiTec HS-311 servo. It is a very close physical match, and it seems to function just as well as the HK version.

Fully extendedFully extended

Programming the Arduino is something that can be a little tricky. I used the “Servo Sweep” code from the Arduino tutorial database, and modified it to work for this specific application. The speed and range of the servo can be controlled using this code, and can be tailored to your particular application. I wanted to test the full range of the servo, so my code rotates the servo motor the full 180 degrees.

Arduino wiringArduino wiring

I chose to cut the connector off of the servo, and wired it directly to the Arduino. The servo is powered from the 5V/Ground pins, and control is sent via Pin8. Power to the Arduino can be supplied either through USB or the onboard 9V connector, although I haven’t tested the 9V input yet.

Finished ProductFinished Product

The finished product looks and feels pretty solid. The servo is fast and tight, and the parts all have a good fit to them. I don’t know how long the fishing line will last, as it is only rated at 30 lbs. The original instructions called for 200 lb. fishing line, so we’ll see how long this will last.

ATTRIBUTION:

Arduino Sweep Code: http://arduino.cc/en/Tutorial/Sweep
InMoov .STL Files: http://www.thingiverse.com/thing:67709
InMoov Blog: http://inmoov.blogspot.com/