TTL Tilt Sensor

Current Part:

2 Axis Accelerometer
Dual or Single Color 8x8 LED
(3) LM339 Quad Comparator
74-244 Octal Buffer
74-238 De-Multiplexer
74-193 Binary Counter
(3) 74-126 Quad Buffer
(3) 74-04 Hex Inverter
74-02 Quad 2-Input NOR
555 Timer
(2) 20 Pin Sockets
18 Pin Socket
(3) 16 Pin Sockets
(9) 14 Pin Sockets
Green LED
7805 +5v Regulator
1uF Capacitor
0.1uF Capacitor
(2) 4.7kΩ Resistor Network
10kΩ Resistors
(2) 2.2kΩ Resistors
(2) 1kΩ Resistors
330Ω Resistors
(5) 100Ω Resistors
100kΩ Variable Resistor
9v Connector
Battery Holder
Wire Wrap
Wire Wrap Tool

Parts List Details
           There's a lot of parts to this project so there's probably one or more that you've never seen before. Don't worry! I've taken the liberty to describe the most important parts in more detail below.

           Protoboard is a type of prototyping board that has holes every 2.54mm (0.1") which is the same pitch as PDIP TTL logic IC's and IC sockets. This means the pins fit perfectly into these boards and from there we can wire wrap the circuit together.

2 or 3 Axis Accelerometer (ADXL 335)
           For this project, I used an ADXL 335 accelerometer on a breakout board. This device is simple, supply between 1.5v - 3.5v and ground and then start watching the output. For this sensor, 0 g-forces on any axis will mean an output of (Supply Voltage)/2. So if we input 3v for power to this accelerometer, the 0g voltage output would be 1.5v for X and Y axis.

Dual or Single Color 8x8 LED Matrix

           This is the LED output display that will represent the tilt magnitude in a recognizeable way. It can display both red and green colors, but must be driven one column at a time. The pinout does not give instantaneous access to all LEDs at once, because of this we need to build a state machine for each LED column.

74-244 Octal Buffer
           Since we want to output the tilt magnitude for X and Y axis, one of the axis will show up on the LED matrix on the same column. This means input to the LED matrix will happen at the same time, so we can use this extended logic buffer for the entire column, with only 1 enable signal.

555 Timer
           The 555 timer is used to drive the state machine very fast, so that the POV (persistence of vision) effect occurs on the LED matrix making the LEDs appear to always be on.

74-193 4-Bit Binary Counter
           This 4-bit binary counter is used to drive the 8 state machine in the 74-238. The A/B/C outputs from this counter are fed into the de-multiplexer constantly changing the state over and over.

74-238 De-Multiplexer
           The de-mux in this project acts as the state machine output. The 74-238 is the same as the 74-138 except that state ouputs are logic high, which is great because the logic buffers we are using are logic-high enabled. For anything that isn't logic-high enabled, we can pass the de-mux output through a hex inverter.

74-126 Quad Buffer
           The 74-244 octal buffer will be used for one display axis, but for the other axis we need to have individual buffers and LED drivers because they occur in different columns. Each buffer in the 74-126 will represent a unique state enabled from the state machine, lighting up certain LEDs on the horizontal axis.