Magician
Robot Controller
The Magician robot controller is a low cost, Arduino compatible controller for beginners
with everything you need to get started all on one board.
Features:
• USB interface and ISP socket for easy programming.
• ATmega8 controller preloaded with the Arduino boot loader (upgradeable).
• Dual motor controller rated at 800mA for each motor.
• Motor control circuit can be disconnected to provide additional digital pins.
• 8x 3 pin servo compatible outputs.
• 6x analog inputs with +5V and ground for powering sensors.
• Servo power selectable between battery voltage or 5V regulated.
• LDO +5V regulator rated at 1.5A when used with a heatsink.
• Reverse polarity protection diode rated at 3A to protect servos.
• Quality screw terminals for power and motor connections.
• Power switch, power LED, reset button and D13 LED.
Arduino Compatibility
The Magician controller uses the ATmega8 processor and comes preloaded with the
Arduino boot loader. The ATmega8 is the chip used by the original Arduino and has
enough program memory to suit beginners (8K). This chip can easily be replaced with an
ATmega168 or ATmega328 to increase memory size while maintaining Arduino
compatibility. This manual assumes you will use the Arduino IDE for programming the
controller.
USB Interface
The USB interface allows the controller to be easily programmed with the Arduino IDE and
a USB cable. When programming the controller can be powered directly from the USB
cable although the USB power will not power the motor control circuit.
Motor Control Circuit
The Magician robot controller has two motor control circuits called “H” bridges. These “H”
bridges will control the speed and direction of small DC brushed motors as used in most
toys.
Each motor is controlled by two digital outputs. The left motor direction is controlled by D7
while it’s speed is controlled by D9. The right motors direction is controlled by D8 while the
speed is controlled by D10.
If your robot does not used DC brushed motors
then you can remove the 4 jumpers next to pins
D7-D10 giving you one male and one female
header for each pin.
D9 and D10 can generate PWM signals when the
servo command is not used.
Digital / Servo pins
There are 8x digital pins configured especially for use with servos. These pins can still be
used as standard digital I/O pins but they also have power pins for servos. +V can be
selected between Vcc (+5V) from the regulator or Vbat from the battery allowing servos to
be powered directly from the battery.
These pins do not have to be for servos. They can also be used with LEDs, simple
switches or digital sensors in which case the voltage select jumper should be set to Vcc
(+5V) to prevent damage.
Note each pin has a maximum current limit of 40mA making them unsuitable for driving
relays or motors directly. When driving LEDs a current limiting resistor of about 270 ohms
should be used in series with each LED. Digital pins D2 and D3 can also be used for
external interrupts.
Analog Inputs
These pins are labeled A0 – A5 and are normally used to measure voltages between 0V
and 5V. There are many sensors available that have analog outputs. If you use a 5V
sensor then it can be powered by the Vcc and ground pins next to the analog input pins.
Note: Some analog sensors do not have the +5V pin in the center of the plug. You must
swap the power wires on the sensor cable to prevent damage to the sensor.
Digital and Analog pins
When the controller is switched on for the first time or reset then all pins except D13 are
converted to inputs. D13 is set to output so that the boot loader can operate it. You will
notice that the LED on D13 flashes when a new program is uploaded. It is recommended
that D13 be used for outputs only for this reason. If you want to use a pin for an output
then you must configure it as an output.
Analog pins A0 – A5 can also be selected as digital pins D14 – D19 allowing them to be
used as digital I/O pins.
All controller pins have an internal 20K pullup resistor available. To enable this pullup
resistor, write a “1” or “HIGH” to that pin while it is configured as an input.
Power Supply
This controller is designed to work with battery voltages from 6V to 9V. Voltages over 9V
will prevent the motor control circuit from functioning correctly. Voltages less than 5.5V can
cause the 5V regulator to become unreliable. A reverse polarity protection diode will
protect your controller if the power is accidentally reversed.
The 5V regulator uses a large copper track on the board for a heatsink and when running
from a 6V battery can easily handle up to 1A of current. If necessary the regulator can be
stood upright on the PCB with a heatsink attached. The maximum current rating of the 5V
regulator is 1500mA.
Software and USB Drivers
The Arduino language is a simplified version of C++ which is easy to learn making it ideal
for students and hobbyist. This software is free and available for Windows, Linux and Mac
OSX. You can download it from:
http://arduino.cc/en/Main/Software
The USB interface drivers are also available for Windows, Linux and Mac OSX. Download
the latest drivers from:
http://www.silabs.com/products/mcu/Pages/USBtoUARTBridgeVCPDrivers.aspx
Magician
Robot Controller
