is the system overview of the project. Different parts of the system
will be explained below.
implement the LED controller, the microcontroller pins required to
independently drive a large amount of LEDs
are reduced to the amount required to communicate
commands to the LED controller. Through those commands, we
will look to
controll the on/off state of each LED, along with its intensity. In
addition, the LED controller will lower
the amount of total circuitry
by avoiding switch transistors and bias resistors for each
testing pictures displays three LEDs at different current steps
controlled by the LED controller. The left is
, while the middle one is on at half of the rated current and the right
one is at full blast.
For the Odometer on the gauge, we
required an LCD that could fit in the limited size on the gauge face.
Size being our
consideration, we opted for the 7-Segment, 7 digit TN LCD. It has fewer
connections to the microcontroller.
microcontroller we chose has a LCD module built in it making it easier
to program this LCD. There are four
levels on the LCD and the voltage difference between the Segment drives
and Commons defines if the segment on
the LCD are on or off.
We used the
LCD PICDEM board to do our testing. In the picture on the right you can
see the LCD displaying 8888.
This was while we were
figuring out what segments were controlled by which combinations of
segment drives and Commons.
layer has holes that fit directly on the LEDs and LCD on
the PCB. Also there are groves milled into the acrylic
for the light
guide to fit into the base layer, to get the light guides really close
to the LEDs. This layer isolates every LED.
acrylic was chosen as it gives a good contrast with the green LEDs.
light guide directs sits in the groves on the base layer.
The main purpose of this guide is to direct the light but
bright enough to be seen. So we chose a clear acrylic for the light
guide. The squares at the end of each guide sits
LEDs on the PEC. Each strand is 10 MPH.
piece sits on the top of the light guide. There are groves
on the botton of the top piece matches with the light guide
the light guide is tightly fit between the bottom layer and top piece.
The top layer protects all the inner layers and
user from the LED brightness.
picture on the right shows our initial design of the light guide. The
strands were separate which made it
implement. So we moved from this design to the single acrylic light
Microcontroller we chose didnt have any EEPROM. To compensate for that
we used the EEPROM Emulation.
took a chunk of the flash memory and treated it like EEPROM. This
worked for us because we had
extra memory, and
because we only needed to store a small amount of data (3 bytes). The
files that microchip made readily available
The left picture is a view
our board level schematic which we made using EAGLE, a layout editting
board has two layers; the top
is 3.3V and the bottom is tied to ground. The PCB contains our PIC
2 LED controllers, the 23 LEDs, voltage regulator and other
components like the resistors and capacitors. The components
in Red are on the top and the blue are on the bottom. As it
is visible in the picture, only the LEDs are on the top and
all the other components are on the bottom, thus not
cluttering up the surface that the base layer of the acrylic would
be sitting on. The
green pins are the header pins used to program the PIC.
The picture to the right is
the bottom of the board after we soldered the components to the board.
The PIC is in the center,
while the 2 LED controller on
the top. At the
bottom is the ribbon cable for the LCD (LCD is on the top but its