The main purpose of the meetings held on Friday (10.10.2008) and Sunday (10.12.2008) was to complete a schematic of the N.M.E system and to work on a program to control the Pico-Servo. The secondary objective was to repair the RC car once again. (Programming portion is on separate post).
After working many hours on the design of the PCB and the components needed, we came up with a schematic of the N.M.E system along with a rough layout of the Printed Circuit Board (PCB). The schematic is composed of ; Prop-plug, EEPROM, Cold Junction Compensator, Op amp, Parallax Micro controller, Analog to Digital Converter, Voltage regulator circuit, Servo controls Datalogger and Thermocouple fig 1.1.
Fig 1.1 Schematic Pin-out
The next step was to design the PCB layout fig 1.2. The layout was obtained by following carefully the details from our schematic.
This two drawings were then submitted to our advisor for revision. Our advisor's revision proved to be important, since a few errors were found and our component layout/organization skills are average. His revisions were used as a final documents fig1.3.
Jorge E Fontanez
N.M.E. Design Team
Our group encountered several problems while working on the servo. For our first attempt on the servo operation, we downloaded servo objects from the Propeller Object exchange on the propeller website. We used demo versions of the Servo32v3 & Servo4 objects. Both versions of the demo compiled successfully and made the servo move. We continuously tried interpreting and modifying the code, but it wouldn't give us our desired horn angles. (The horn is the piece attached to the top of the servo motor).
On October 14th & 15th, team member, Justin, tried individually working on the code of the servo. Progress was still unsuccessful.
In addition, we put the main code of the datalogger and ADC into two new seperate Cogs in the Propeller program so the devices may run efficiently. It makes the main PUB a lot simpler and more organized. The program compiled and operated successfully.
A major problem that occurred as we were working with the servo. Whenever we would add our servo program into the Propeller code, the datalogger would not function correctly. Whether we put the initiated servo program into a new cog or called it as a function, the servo would operate, but the datalogger was ignored. So trying to run the servo simultaneously with the ADC & datalogger was unsuccessful.
Definition and purpose of a Cog is described below:
(Referenced from Dr. Ducharme's Propeller Intro Power Point Presentation.)
-Each of the 8 microcontrollers is referred to as a Cog.
-The Cogs each have their own RAM for registers and program use (local variables)
-They share the same Main Memory using a common bus.
-They all have access to all the input/output pins P0-P31.
So currently we have 3 Cogs operating in our propeller chip. One Cog operates the main, second for the datalogger, and the third for the ADC.
Our group also purchased new set of wheels and other accessories for our R/C car.
N.M.E. Design Team
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