TTL Tilt Sensor

Project Info
Author: Chris
Difficulty: Medium-Difficult
Time Invested: 9 Hours

Take a look at the above
tutorials before continuing
to read this tutorial.
           The last project I built, the Masochist's Video Card reminded me of how fun pure TTL digital design can be and since the 7400 contest seems to be allowing multiple entries, I figured why not build something else?
           The accelerometer is an interesting sensor that is now extremely tiny thanks to MEMS technology. Specifically, the accelerometer senses gravity, and since earth has a constant 1 g-force always pulling toward the center, we can use that reference to find the tilt of any object. With some digital design and LEDs added to the mix we can even build a tilt sensor as I will show you in this article.

Tilt Sensor via Accelerometer - Demonstration

Tilt Sensor via Accelerometer - Setup

Tilt Sensor via Accelerometer - Board

Purpose & Overview of this project
           The purpose of this project is to build a working tilt sensor. The tilt sensor should have 3 core components:
  •     [1] A Custom Comparator Based Analog to Digtal Converter
  •     [2] An 8-State Machine To Drive The LED Matrix
  •     [3] Logic Buffers To Connect The A/D To The LED Matrix Display
These 3 components form the entire system design, with the first 2 being independent of each other and the last component combining both sides of the circuit. In order to 'display' tilt in a recognizeable way, the only LEDs that will be used, will be the center two, horizontally and vertically like a '+' sign.
           The custom analog to digital converter should use a multiple resistor voltage divider for reference voltages. It should be designed in a way so that the reference voltages reflect various 'degrees' of tilt from the accelerometer's analog output. The 8-state machine should use a 555 timer, a 74-193 binary counter and a 74-238 de-multplexer. The state outputs should be used as enables signals into the LED driving logic buffers. This will allow the LED matrix to reflect the current tilt magnitude based off of the a-to-d output.