Cornell University  Spring 2002 
Professor Bruce Land
Digital Hourglass
Akosua Kyereme-Tuah     Andrew K. Lee     Susan Li-Wen Lin
[Home]     [Hi-Level] [Hardware] [Software] [Results]
  • The digital hourglass performed well. By putting in two accelerometers, we were able to get a full range tilt angles. The hardest part of the project was getting the LCD to work. Because of our bad luck, we happened to pick a bad programming board each time we tried to get the LCD to work. But upon finally getting it to work, everything else involved coding issues.
  • Drawing the sand was complicated due to the LCD only being able to write bytes, rather than bits. While writing the algorithms, we just had to make sure that exceptions were checked for and taken care of.
  • Finding the position of the sand was done by visualizing the various possible sand positions and calculating it in relation to the area of the sand in the hourglass. We tested this part in Matlab and it worked beautifully.
  • One thing we had to be careful about was the data types. In doing simple mathematical equations, we had to make sure that the data types were the same. If they were not the same, then casting had to be done.
  • The accelerometer worked with no problems. We soldered the accelerometers on a board made by Professor Land and tested it with the oscilloscope. The main issue with the accelerometer involved having to output voltages that were less than the Aref (from the A/D on the STK200). We were able to lower some voltages, yet maintain a large enough range of voltages by simply putting in resistors.

The Complete Setup (Left: Two accelerometers on breadboard; Middle: LCD; Right: MCU)

Hourglass tilted at "90" degrees

Hourglass tilted at "45" degrees

  Next Time  

If time permitted or in future improvements of this project, the following additional features can be added:

  • Make a curved hourglass and be able to draw in curved sand positions.
  • Develop an algorithm that takes timing and amount of sand into consideration so that a real clock can be made out of the hourglass.
  • Package the hourglass so that it is a stand-alone component.
  • Add music (i.e. Jeopardy music) so that one can listen to sound as he thinks.