System Overview



This is the system overview of the project. Different parts of the system will be explained below.


LED Controller                                                      LED Testing

                                                                                  

                                        By 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 LED.

                                        The LED testing pictures displays three LEDs at different current steps controlled by the LED controller. The left is
                                        barely on , while the middle one is on at half of the rated current and the right one is at full blast.    

 

LCD Odometer function                                                LCD Testing

                   
    
                                        For the Odometer on the gauge, we required an LCD that could fit in the limited size on the gauge face. Size being our
                                        biggest consideration, we opted for the 7-Segment, 7 digit TN LCD. It has fewer connections to the microcontroller.
                                        Also the microcontroller we chose has a LCD module built in it making it easier to program this LCD. There are four
                                        bias 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.



          Display Breakdown                                       Display Testing          

                                                              

                                        The Base 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.
                                        The black acrylic was chosen as it gives a good contrast with the green LEDs.

                                        The Acrylic light guide directs sits in the groves on the base layer. The main purpose of this guide is to direct the light but
                                        still be bright enough to be seen. So we chose a clear acrylic for the light guide. The squares at the end of each guide sits
                                        on the LEDs on the PEC. Each strand is 10 MPH.

                                        The Top piece sits on the top of the light guide. There are groves on the botton of the top piece matches with the light guide
                                        strands. So the light guide is tightly fit between the bottom layer and top piece. The top layer protects all the inner layers and
                                        shields the user from the LED brightness.

                                        The testing picture on the right shows our initial design of the light guide. The strands were separate which made it
                                        difficult to implement. So we moved from this design to the single acrylic light guide design.

                                        
EEPROM Emulation
 

                             
                                        The Microcontroller we chose didnt have any EEPROM. To compensate for that we used the EEPROM Emulation.
                                        This Method took a chunk of the flash memory and treated it like EEPROM. This worked for us because we had
                                        plenty of extra memory, and because we only needed to store a small amount of data (3 bytes). The emulation required
                                        some extra files that microchip made readily available
                                        
                         

PCB Fabrication

           

                                     The left picture is a view our board level schematic which we made using EAGLE, a layout editting software. This
                                     board has two layers; the top is 3.3V and the bottom is tied to ground. The PCB contains our PIC processor, LCD,
                                     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 connector
                                     is on the bottom).