Robots made easy
- 2. Peel Training Day Robots Made Easy
- 3. Using the PICAXE Microcontroller This presentation will show you: How to connect the PICAXE on breadboard How to hook up sensors How to wire up drive motors How to download a program
- 4. We will be using the PICAXE 20-X2, however there are many kinds of PICAXE microcontrollers. They start as small as 8 pin and all the way to 40 pins.
- 5. PICAXE 20-X2 Made by Revolution Education and uses Microchip PICs Has a program loaded on the chip that allows the program to be written in a form of BASIC and can be downloaded using a serial port and three wires. Each pin can be set up to perform several tasks. Can run over a voltage range 2.1V to 5.5V
- 6. The Breadboard Hook up power and ground. Hook up serial port circuit. Hook up line following circuit. Hook up servo motor. Hook up motor driving circuit.
- 7. Sensors The line following sensors (OPB703WZ) works by detecting infra-red light. The diode emits IR light which bounces off the surface. The reflected light then turns on the photo transistor relative to the amount of light reflected. The circuit then provides an analog value which is then read by the microcontroller and converted into a digital value.
- 8. Sensor on White Surface If the surface the light is reflecting off of is white, more IR light is reflected thus turning the transistor on fully. This will bring the output close to 0V. (So the theory goes…)
- 9. Sensor on Black Surface However, if the IR light is being reflected of a dark surface, the amount of IR reaching the photo transistor will be greatly diminished resulting in the transistor being almost off and the output from the circuit being close to 5V.
- 10. Motor Control with L293D Half-H Driver Make an H-Bridge with the two drivers. External diodes not required with L293D. Ground pins: 4, 5, 12 & 13. Pins 1, 8, 9 & 16 to +5V. Pins 1 & 7 control motor connected to pins 3 & 6. Pins 10 & 15 control motor connected to pins 11 & 14. Motor should have a 0.1uF capacitor across the terminals (not shown here). Pin 2 or 15 Pin 7 or 10 Motor Direction L L Stop L H CW H L CCW
- 11. Servo Servos is a three wire DC motor that can be directed to a specific position by sending a specific pulse width. The standard servo can travel a max of 180°, whereas a modified servo can continuously move in a direction of CW or CCW depending on the pulse width sent. PICAXE has a special command that will let you set the position of the servo. Servo has three wires: Black – negative, Red – positive and White – signal. For sample commands see page 19 of PICAXE Manual 3. Also page 30 for the thermistor.
- 12. Writing the Program There are two methods of writing a program. 1) The flowchart method and 2) the program language method.
- 13. Simple Line Following Program
- 14. Downloading the Program. Make sure: Code is written without any syntax errors. Power is on. Cable is connected to the serial port and the PICAXE. Correct PICAXE is selected. Correct com port (serial port) is selected.
- 15. Thanks for coming out!