EENG 200 Mobile Robot Details

Robot general description:

The Robots were used in the EENG 227 lab and were custom designed in the summer of 1999. They consist of a main circuit board, a three-wheel platform, and a prototype board. The three-wheel platform consists of two drive wheels and a third swivel wheel. The robot changes course by varying the speed and or direction of rotation of each drive wheel. The swivel wheel is for stability. The robot has an array of optical sensors, which are used to detect a black line on a white surface. Using analog control circuitry the robot can then be made to follow a closed course consisting of this black line. Much more complex strategies are possible by using the on-board Basic Stamp microcontroller and associated resources to create an analog/digital hybrid system.

The care and feeding of your robot:

1. Follow the cautions and warnings in the ProtoBoard connection section.
2. DO NOT change circuit wiring with the robot power on.
3. Review the robot schematics before attempting to connect your circuit to the robot.
4. When testing robot circuit, use a block to lift the wheels off of the test platform until ability to control motor speed is proven.
5. NEVER give the robot forward velocity when captured on the test platform.
6. Keep the charger plugged into the robot when working on the bench to maintain the battery.

Examples of student robots:

Note how the orderly wiring and component placement on these robots makes debugging easier.

Schematics: Circuit Descriptions

These schematics are of the Mobile Robot main circuit board.

Page 1: Power Schematic (Power available for student circuitry)

Page 2: Analog Schematic (Circuitry to operate the motors)

Page 3: Digital Schematic (Basic Stamp circuits)

Page 4: Sensor Schematic (Small sensor PC board)

Key elements:

• Basic Stamp Chip - The BS2-IC runs a variation of Basic. Programs are downloaded from the PC using the 9-pin "D" connector on the main circuit board. Sample programs are on each workstation in the Basic Stamp directory.

AtoDTEST.bs2 (Test program that demonstrates the use of the on board A/D converter)

LCDTEST.bs2 (Demonstrates the use of the robots LCD display)

DtoATEST.bs2 (Demonstrates the use of the D/A output)

AnalogSWTEST.bs2 (Demonstrates how to use the analog switches)

These programs can be integrated into student programs and modified to create custom functions on the robots.

• LCD display - A 2 line by 16 character display is available to display status information.
• Motor Controllers - A motor controller is used for each drive wheel. Each wheel's speed can be varied as well as it's direction of rotation.
• Battery - A +12V 1.3AH sealed lead acid battery is used to power the robot. This will give several hours of operation before needing to be recharged. When not using the robot it is recommended that the unit be left on charge.
• ProtoBoard area - A solderless prototyping area is provided on top of the robot. The ProtoBoard can accommodate a maximum wire size of #22. Anything larger can damage the board.

• Status LEDs - LEDs are used to indicate the right and left motor status. Green arrow for reverse and red square for stop.
• Test Points - Test points are provided for all supply voltages and the right and left motor speed voltages. This aids in the debugging of circuits.

TP1 (+5 VDC)

TP2 (+V Battery)

TP3 (Ground)

TP4 (+15 VDC)

TP5 (-15 VDC)

TP6 (Right speed)

TP7 (Left speed)

• Controls - A reset button S1 is provided to reset the BasicStamp. Power to the robot is controlled by on/off switch SW1

Important links for understanding and utilizing the Robot circuitry:

Basic stamp: Parallax, Inc. or Detailed Basic Stamp Information

LCD display: Scott Edwards Electronics Note: When viewing the web site there are old and new displays shown. The robots have a mixture of displays. The new display programs the same as the old one so use the manual for the old one as a programming reference.

D to A converter: MAX518

A to D converter: ADC0834

OpAmp: LM324

Voltage Comparator: LM311

Analog Switches: DG201

Motor Controller: KA8301 or BA6209

Phototransistor: QSD424

Transistor Driver: ULN2003A

ProtoBoard interconnection points:

Basic Stamp: Connectors JP4 and JP4A (DIGITAL I/O) are the Basic Stamp I/O connections.

When a program begins all of the pins are inputs. You must program a pin to be an output. Be sure the pin is wired correctly before applying power to circuit.

The maximum voltage on JP4 and JP4A pins is +5V

NEVER connect these pins to a negative voltage.

Motor Control: Connectors JP2 and JP2A (CONTROL) are the control lines for the right and left motors.

STOP RIGHT, REV RIGHT, STOP LEFT, and REV LEFT are all logic inputs

The maximum voltage on these pins is +5V

NEVER connect these pins to a negative voltage

SPEED RIGHT and SPEED LEFT are the motor speed controls

The maximum voltage on these pins is +15V

NEVER connect these pins to a negative voltage

ANALOG RIGHT and ANALOG LEFT are bi-directional motor speed controls. If the input to these pins is a negative voltage the motor will reverse direction at a speed indicated by the absolute value of the voltage.

The voltage range on these pins is +15V to -15V

The rest of connector JP2 and JP2A are for the spare LEDs and drivers.

Power Supplies: Connectors JP1 and JP1A (POWER) provide the power supplies needed to run the circuitry implemented on the ProtoBoard. Two pins on each connector are provided for each voltage. (+5, +15, -15, Vbattery, Ground)

Do NOT connect the different voltages to each other.

Analog Inputs (A/D): Connectors JP5 and JP5A (ANALOG IN) are inputs to the ADC0834 A/D converter.

The maximum voltage on these pins is +5V

Analog Outputs (D/A): Connectors JP3 and JP3A (ANALOG OUT) are outputs from the MAX518 D/A converter.

The maximum output voltage on these pins is +5V

NEVER connect these pins to any voltage supply.

Analog Switches: Connectors JP6 and JP6A are inputs and outputs to the DG201 analog switch.

The voltage range on these pins is +15V to -15V

Sensors: Connectors JP7 and JP8 are used to bring the sensor signals up to the ProtoBoard. JP7 and 8 are wired in parallel with JP7 usually being used to terminate the wires from the sensor board and JP8 serving as a connection to the ProtoBoard.

JP15 on the sensor board

Pin 1 is the anode of the IR LED string

Pin 2 is the collector of the phototransistor Q1

Pin 3 is the collector of the phototransistor Q2

Pin 8 is ground for the IR LED string and the emitters of Q1 and Q2

JP15 on the sensor board is connected to JP7 on the main board by a 4 conductor multicolored cable.

This cable connects the sensor board to the main board as follows:

JP15 pin 1 anode of IR LEDs	JP7 pin 8	JP8 pin 8
JP15 pin 2 Collector of Q1	JP7 pin 7	JP8 pin 7
JP15 pin 3 Collector of Q2	JP7 pin 6	JP8 pin 6
JP15 pin 8 Ground	JP7 pin 5	JP8 pin 5

JP8 on the main circuit board is where the student circuit is connected.