• Pictures courtesy of Peter Wen

I worked with Soheil Koushan, Mahan Nekoui and Peter Wen to design a tachometer (a device that measures the speed of a spinning object). The project had three main constraints:

  1. The device cannot come in contact with or impede the motion of the object it is measuring.
  2. Programmable chips cannot be used.
  3. The entire project must cost less than $150.

Our tachometer measures revolutions per second, revolutions per minute and revolutions since last reset. The device is accurate to a tenth of a revolution and displays four significant digits.

I was chiefly in charge of the digital logic of the tachometer (basically whatever’s inside the big black box). The circuit was designed to have only basic electrical components and 4000 series ICs to comply with the constraints. My circuits calculated and displayed the appropriate reading based on a digital pulse from the sensor. I also designed the physical layout of the tachometer, supervised the soldering of the circuitry and performed troubleshooting of the device.

Our project proposal can be found here (contains preliminary circuit diagrams and sketches). The operations manual can be found here.

If I were to redo the project, I would implement a synchronous circuit design and remove the very rudimentary delay that I implemented at 3 am the day the proposal was due. A more robust multiplication unit was omitted since create one from logic gates would be prone to difficulty while soldering and would take up too much space.