Tekstvak: Electronic circuits

The microcontroller is the heart of the robot. We used the PIC16F876 (the 28 pin version). To avoid ‘double booked’ pins in the program, we made a list of the used pins: 

Note: After some hours searching, we found out pin 26 of the microcontroller didn’t work. 
The digit0 of the highest wide IRsensor was therefore placed on pin 27.
There are some other things to consider by making the scheme for the controller, like voltage, PICkit, crystal...
The microcontroller (and other parts in the electronic circuits) must be powered by 5V. To create this voltage out of the battery pack of 12V, we used a voltage regulator LM 7805.
Note: The voltage regulator will become very hot, so it’s a good idea to provide a (large) heat sink. 

Clock frequency
The microcontroller runs on a specific frequency. This clock frequency is delivered by an oscillator (crystal). All the operations of the microcontroller run at this signal. Make sure to place the oscillator as close as possible to the microcontroller to avoid noise. OSC1 and OSC2 are pins 9 and 10 of the microcontroller. The circuit is as follows:

We are using InCircuit Serial Programming (ICSP), which means we can program the microcontroller without removing the chip from the board. The connections needed for this microchip looks like in the figure below. 
The used pins of the microcontroller are:

And at last we also integrated a reset button, in case the program is blocked or stopped. (MCLR = pin 1, Vdd = pin 20)

In Traxmakr it looks as follows: 

Note: The width of the microcontroller isn’t correct, which made the connection a bit difficult.

Tips for designing PCBs
Check the dimensions of the desired components first, it will save you a lot of time fixing wrong placed holes on the PCBs!
To save time during chemical etching of the PCB, leave as much as possible bottom layer (blue in our figures). Make sure you keep the GND the biggest, because you’ll make antennas otherwise.
To make the connections with the other boards, make sure they are combined at the border (at least with 2 or 3 connections together).  
Note: The PCB files can be downloaded on the page ‘Results and thanks’.

Matthias Borremans, Joost Geeroms, Frank Jonckheere and Sara Van Rossem

Design and building of a football playing robot

   i, BallL
(handsome) intelligent Ball Locatorh

Project Mechatronics 2009-2010                   VUB