CE 351 2020 Fall
Lab 3: SSD Control
Nic Theobald
nstheobald@fortlewis.edu

SSD Control

Introduction
Arduino can simplify the control of outside systems. With only a few pins, LEDs can be flashed, transistors can be activated, and signal can be generated. However, the arduino only has so many pins. Microcontroller boards that have fewer pins can greatly benefit from pin reduction techniques such as shift registers and digital decoders.

Materials
Material List
Item
 X
Arduino IDE
 1
22 OHM R
 11
Arduino
 1
LED
 8
SSD
 1
4 dig SSD
 1
Shift Register
 1
Digital Encoder
 1

Abbreviated Methods
The single SSD was connected to the arduinos digital pins out. The pins were turned on and off in order to flash the SSDs. Next the SSD was connected to a Digital Decoder that took in a 4 bit binary number and used its internal logic to switch on an off its own pin outs. Next, the SSD was connected to a shift register that required a clock signal, a data pin, and a latch pin. The shift register output pins were connected to the SSD. The same was used for the four digit SSD.

Results

Task: Flashing Pin 13

The first step in this lab was to flash pin 13...

Figure 1: Manually displaying numbers on SSD.

Task 1: Manual Switching

The arduino was directly connected to the SSD through 220 OHM resistors. Numbers could be displayed by connecting and disconnecting pins manually.
 
Figure 2: Manually displaying numbers on SSD.

Task 2: Digital Decoder Switching

The Digital Decoder was then added to reduced the number of pins and to make the number changing process a little more automated. A bit mask was used to interpret the desired number and set the appropriate arduino pins to HIGH or LOW.


Figure 3: Bit mask used to assign High and Low values to Arduino pins.



 
Figure 4: Using Digital decoder to display numbers on SSD.

Task 3: Shift Register Switching

The SHift Register was then added to reduced the number of pins to 1 and to make the number changing process even more automated. A following code was used to determine the desired sequence and set the appropriate arduino pins to HIGH or LOW.

.
Figure 5: Shift register IC and Schematic.


Figure 5: Code for controlling shift register

 
Figure 6: Using Shift Register to Sequence Leds
A single digit SSD was then put in the place of the LEDs.


Figure 7: Code for controlling shift register


Figure 8: Using Shift Register to Sequence SSD

The single digit SSD was then replace by a four digit SSD and the code was changed to display "2019". The following code was inserted into a four loop in order to change the delay over time (for visualization purposes). The code worked by sending 2 to all of the digits but at the same time only activating digit one. Then it would send 0 to all of the digit but only activate digit 2, and so on...


Figure 9: Using Shift Register to flash 2019.


Figure 10: Flashing of "2019" at ever increasing delays.


Figure 11: Flashing of "2019" at constant super fast speed.


Discussion
This lab ultimately demonstrated the power of using shift registers and digital decoders. Both devices are massively useful in the optimization of output signals.