Buying List

U.S.-based vendors, year 2012
Item Vendor Price Unit
Arduino MEGA 2560 Arduino $50 1
Encoder (1250 CPR) US Digital $75 1
Encoder (500 CPR) US Digital $65 1
Motor (0-COPAL50-6) Robot MarketPlace $25 1
Motor Controller (0-PL1372) Robot MarketPlace $35 1
Large Pulley (1375K53) McMaster $15 1
Small Pulley (1375K21) McMaster $10 1
Belt (1679K84) McMaster $1 1
Battery (9V) convenient sotre $4 1
Mechanical parts self made - -
Total cost: approximately $280

Machenical Structure

The mechanical parts was made by a 3D printer. The Autodesk Inventer design files are available in DOWNLOAD section. I and my MakerBot 3D printer:

3Dprinter

This photo was taken when I just finished assembling the 3D printer--MakerBot Thing-O-Matic. It took me 26 hours continuously working on the assembly. (April 1st, 2012)

Pendulum Base

Part1.ipt and Part2.ipt construct the pendulum base. The 500 CPR encoder is fixed in the left, and the motor is under the large pulley.

Arm

Part3.ipt and Part4.ipt construct the arm. A copper rod is in between Part3 and Part4 to make the arm more rigid.

Pendulum

Drill a hole to the pendulum, and connect to the encoder shaft directly.

Electrical Diagram