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GREYBOT V.1 ATMEGA 16 BASED ROBOTIC PLATFORM

USER MANUAL

Designed by:

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INDEX

Sr.No Content Page No.

1. Product Description 4

2. Features 5

3. Technical Specifications

3.1 Micrcontroller

3.2 Programming

3.3 Indicators

3.4 Locomotion

3.5 Power

3.6 Sensors

3.7 Operational Modes

3.8 Communication

3.9 Dimensions

3.10 Software Support

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4. Block Diagram 8

5. Using GreyBot V1.0

5.1 Powering Up GreyBot

5.2 Power Management System on GreyBot

5.3 Regulated Supply for onboard payload

5.4 Battery Charging Procedure

5.5 Motion Control

5.6 PWM for Velocity Control

5.7 Micocontroller Pin Connections

5.8 Infrared Proximity Sensor

5.9 Line Follower Sensor

5.10 LCD Interfacing

5.11 User Programmable Pins

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5.11.1 LED’s

5.11.2 Buzzer

5.11.3 Swi0tches

5.12 Battery Voltage Swing

6. Optional Interfaces

6.1 Servo Motor

6.2 Ultrasonic Sensor

6.3 Combination of Servo Motor and Ultrasonic Sensor

6.4 Magnetometer Interface

6.5 Bluetooth Module Interface

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7. Contact 21

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1. Product Description

GreyBot V.1 is a low-cost robot designed by GreyRobotics that will help you get acquainted with

robotics and embedded system platform. With its unique software and hardware design, you will

be able to design and run various robotic based applications both simple and complex. It is a

versatile platform created for the use of beginners as well as researchers so as to ease their work.

Hobbyists and enthusiasts can earn expertise in robotics by developing algorithms and test them

on GreyBot. Its architecture allows you to control the robot using AVR microcontroller. It is

powered using high performance, rechargeable Lithium Ion battery of 3.7V/2.5A rating. Auto cut-

off battery charger is provided for charging the robot. It comes along with our easy to use Line

Follower Sensor Array which can be used for developing the path following algorithm for the bot.

Long distance Infrared Proximity Sensor is provided. High speed motors help you to give the robot

its locomotion. Motor control is achieved using H-bridge motor driver. The onboard 16x2

alphanumeric display along with user switches can be used to select various operating modes of

the robot. Also, it has user programmable LED’s and buzzer.

The robot has additional pins to interface Magnetometer, Ultrasonic Sensor, Servo Motor and

Bluetooth module as per the user application. We also provide an inbuilt firmware for basic testing

and functioning of the robot. The robot can be programmed using ISP port.

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2. Features

▪ Comes along with a Line Follower Sensor Array of 6 developed by GreyRobotics for

path following application.

▪ Long Distance IR Proximity Sensor for obstacle detection

▪ Two user programmable LED’s.

▪ Two user programmable Switches.

▪ User programmable buzzer as audio output device.

▪ LCD display for easy user access.

▪ On board motor driver.

▪ User accessible PWM pins for speed control of motor

▪ Lithium Ion battery with auto cut-off charger.

▪ ISP port for programming.

▪ Direct plugin HC-05 Bluetooth facility (optional).

▪ Pins available for interfacing of Magnetometer, Servo Motor and Ultrasonic Sensor

(optional).

▪ Easy to mount slot for Servo Motor (optional).

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3. Technical Specifications

3.1 Microcontroller –

ATMEL ATMEGA16

3.2 Programming –

Using USB ASP Programmer via ISP port.

3.3 Indicators –

▪ 16x2 Character LCD

▪ 2x User Programmable LED

▪ 1x Power Indicator LED

▪ Buzzer

3.4 Locomotion –

▪ Two DC geared motors (200-300 RPM)

▪ Caster wheel as support

▪ Top Speed: 0.5m/second

3.5 Power –

▪ Single 3.7V Li-On battery

▪ Smart charger with indicators

▪ On board power boost module

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3.6 Sensors –

• IR Proximity Sensor

• Line Follower sensor array 6 developed by GreyRobotics

• Ultrasonic range sensors (Optional)

• Magnetometer (Optional)

3.7 Operational Modes –

▪ Test Mode

▪ Line follower mode

▪ Standalone (Autonomous Control)

▪ Distributed (multi robot communication)

3.8 Communication –

▪ Bluetooth module.

▪ USB to TTL for serial communication.

3.9 Dimensions –

▪ 140x130x100 mm

3.10 Software Support –

▪ Compiler - ATMEL Studio, WINAVR

▪ Burner - AVRDudess

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4. Block Diagram

Figure 1: System Block Diagram of Greybot

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5. USING GREYBOT V1.0

Figure 2: Top View

Figure 3: Bottom View

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5.1 Powering up Greybot –

Greybot is powered by 18650 series single cell lion rechargeable battery. Battery has 3.7volt and

2.5Ah capacity. For safety during transportation, robot’s battery connector is disconnected.

Connect battery to the connector. Before connecting the battery pack or inserting 2 pin relimate

connector in the given socket, make sure that the Power Switch of the robot is off. You need to

charge the battery before your first use. Use the charging module provided along with the robot

accessories. Refer to the battery charging procedure section of the manual.

5.2 Power management system on the Greybot –

Greybot is powered by using a single cell li-ion rechargeable battery. When it is fully discharged

voltage drops to about 3V. Battery pack should not be discharged below 2.8V. Power management

block on the Greybot performs following functions:

1. Regulated supply for onboard payload.

2. Battery charging when robot is powered off and when external battery charger is connected.

5.3 Regulated supply for onboard payload –

Switching regulated technique is used to provide power supply to the GreyBot. It performs boost

regulation to get a constant output voltage irrespective of any changes in the input supply voltage.

It boosts up the battery voltage to 8.2V and then using a linear regulator this voltage is stepped

down to 5V.

5V System: Powers microcontroller, logic circuit and sensors.

8.2V System: Powers Motor driver.

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5.4 Battery Charging Procedure –

Before connecting the battery pack or inserting the 2 pin relimate connector in the socket provided,

make sure that the power Switch of the robot is off. You need to charge the battery before its first

use. Use charging module provided along with the robot accessories. Connect its one end to the

charging port of the robot and the other end to the USB terminal of a laptop or computer.

The battery status can be monitored through the status LED of the charging module (TP4050)

which switches from RED to YELLOW on full charge. On full-charge, it will automatically cut

off the supply from the charger. GreyBot is now ready to run!

5.5 Motion control –

Greybot comes with 250 RPM DC geared motors in differential drive configuration along with a

caster wheel for support. Robot has a top speed of about 0.5m per second. Using this configuration,

the robot can turn with zero turning radius by rotating one wheel in clockwise direction and other

in counterclockwise direction. Robot’s motors have built-in clutch for protection of the motor’s

gears from non-continuous wheel stalling. Motion control involves direction control and velocity

control. Motors are controlled by L293D Dual motor driver which can provide up to 600mA of

current to each motor. To change the Direction of the motor, appropriate logic levels (High/Low)

are applied to L293D’s direction Control pins. Velocity control is done using Pulse Width

Modulation (PWM).

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5.6 Pulse Width Modulation for velocity control –

Pulse width modulation is a process in which duty cycle of constant frequency square wave is

Modulated to control power delivered to the load i.e. motor. Duty cycle is the ratio of ‘T-ON/ T’.

Where ‘T-ON’ is ON time and ‘T’ is the time period of the Wave. Power delivered to the motor

is proportional to the ‘T-ON’ time of the signal. In case of PWM the motor reacts to the time

average of the signal. PWM is used to control total amount of power delivered to the load without

power losses which generally occur in resistive methods of power control.

Figure 4: Pulse Width Modulation (PWM)

Above figure shows the PWM waveforms for motor velocity control. In case (A), ON time is

90% of time period. This wave has more average value. Hence more power is delivered to the

Motor. In case (B), the motor will run slower as the ON time is just 10% of time period. In the

figure 3.10 area marked with the red border are the LEDs connected to the input stage of

The L293D motor driver. Area marked by Blue border shows LEDs connected to the output of

The motor driver. Orange border marks position encoder output LEDs. Yellow border marks left

And right motor connectors.

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5.7 Microcontroller pin connections –

Microcontroller Pin Function

Microcontroller

Pin

Function

PB3(OC0) Pulse width modulation for the left motor (velocity control)

PD7(OC2) Pulse width modulation for the right motor (velocity control)

PC4 Left motor direction control

PC5 Left motor direction control

PC6 Right motor direction control

PC7 Right motor direction control

Table 1: Motor Pin functionality

DIRECTION LEFT

PC4

LEFT

PC5

RIGHT

PC6

RIGHT

PC7

PWM

PB3- PD7

FORWARD 1 0 0 1 As per velocity

requirement

REVERSE 0 1 1 0 As per velocity

requirement

LEFT (Left Motor Forward, Right

Motor Stop)

0 0 0 1 As per velocity

requirement

RIGHT(Left Motor Stop, Right

Motor Forward)

1 0 0 0 As per velocity

requirement

HARD LEFT (Left Motor

Reverse, Right Motor Forward)

0 1 0 1 As per velocity

requirement

HARD RIGHT (Left Motor

Forward, Right Motor Reverse)

1 0 1 0 As per velocity

requirement

STOP X X X X 0

Table 2: Pin Functions for Motion Control

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ACTION MOVEMENT ACTIOPN MOVEMENT

FORWARD

SOFT LEFT

REVERSE

SOFT RIGHT

HARD LEFT

STOP

HARD RIGHT

Table 3: Directions of Motor

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5.8 Infrared proximity Sensors –

Infrared proximity sensors are used to detect proximity of any obstacles in short range. IR

Proximity sensors have about 20cm sensing range. In the absence of any obstacle there is no

reflected light, hence no leakage current will flow. Through the photo diode and output voltage of

the photodiode will be around 5V. As obstacle comes closer, more light gets reflected and falls on

the photo diode and leakage current flowing through the photo diode starts to increase which

causes voltage across the diode to fall. IR LED consume about 25mA current. IR sensor is

connected to ADC Channel 7.

5.9 Line follower sensor –

Array of 6 analog Line Follower Sensor developed by GreyRobotics are used for detecting white

line on the ground surface. White lines are used. To give robot sense of localization. White line

sensor consists of a highly precise IR photo Trans-receiver module for line sensing and IR LED

for the illumination. Due to the directional nature of the photodiode it does not get affected with

ambient light unless it is very bright. When the robot is not on a white line, amount of light reflected

is less hence less leakage current flows through the photo diode. In this case, the line sensor gives

an output in the range of 4 volts to 5 volts. When the sensor is on a white line, more light gets

reflected resulting in considerable increase in the leakage current which causes voltage across the

sensor to fall between 1.5 to 0.1V.

Table 4: Pin Functions for the Motion Control

Sr. Symbol Parameter

1 Vcc Supply voltage

2 Gnd Common circuit ground

3 A0-A5 Analog output pins

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5.10 LCD Interfacing –

Figure 5: 16x2 LCD Interfacing

Microcontroller LCD PINS Description

VCC VCC Supply voltage (5V).

GND GND Ground

PB0 RS Register Select

PB1 R/W READ /WRITE

PB2 EN Enable

PB4 - PB7 D4 - D7 Bidirectional Data Bus

Table 4: 16X2 LCD Pin Outs

To interface LCD with the microcontroller in default configuration requires 3 control signals and

8 data lines. This is known as 8-bit interfacing mode which requires a total of 11 I/O lines. To

reduce the number of I/O ports required for LCD interfacing we can use 4-bit interfacing mode

which requires 3 control signals with 4 data lines. In this mode higher nibble and lower nibble bits

of commands/data set needs to be sent separately. Figure 5. shows LCD interfacing in 4-bit

Mode.

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5.11 User Programmable Pins –

5.11.1 LED’S

User can use two LED’s as output indicators. They can be used for indicating completion of

various states in the program code. The LED’s are connected on PINC2 and PINC3. These pins

are configured as ACTIVE HIGH.

5.11.2 Buzzer

Robot comes along with a 3 KHz piezo buzzer. By setting up the jumper pins, user can select

buzzer or else ultrasonic sensor. It can be used for debugging purpose or as attention seeker for a

particular event. The buzzer is connected to PD5 pin. It is configured in ACTIVE HGH mode Ref

fig 6

Figure 6: Buzzer/Ultrasonic sensor selection jumper

5.11.3 Switches

Two user programmable switches have been provided as inputs. They can be used as external

hardware interrupts. They are available on PIND2 (INT0) and PIND3 (INT1). The switches are

initially pulled high. When the switch is pressed, the pins are pulled down to 0v.

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5.12 Battery voltage sensing –

A resistor network is used to scale down the battery voltage below 5V and given to the

ADC6 pin of the microcontroller. Voltage divider network will give half of the

Battery voltage value to the ADC6 of the microcontroller. If ADC is used with 10-bit resolution,

use the following formula for getting the battery voltage level:

Battery voltage = 2 x ADC 6 value of 10-bit resolution x 5V/1024

6. OPTIONAL INTERFACES

Figure 7: Additional Interfaces of Greybot

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6.1 Servo Motor –

Servo motor is an optional interface on Greybot. 0.9kg torque micro-gear servo motor can be

interfaced. It operates on PWM signal which is generated by the timer control section of

ATMEGA16 microcontroller. User can program servo motor by PD4 pin (OC1B Register). Servo

motor can be easily fixed into the servo slot of level-1 stack of GreyBot. Also, any device can be

used to mount on the servo motor shaft to provide it a rotational motion. For example, an Ultrasonic

Sensor can be mount on the servo to help robot detect obstacle in various directions.

6.2 Ultrasonic sensor –

HS-04 Ultrasonic sensor can be interfaced on GreyBot. PIND5, PIND6 are used to connect the

sensor. It provides long distance obstacle detection to find out obstacles in the travel path of the

robot.

6.3 Combination of servomotor and ultrasonic sensor –

Ultrasonic sensor can be mount on a top of a servo motor and by rotating servo motor as well as

simultaneous scan of an ultrasonic sensor, user can get 180-degree scan its surrounding

environment. This feature can be used in robotic localization.

6.4 Magnetometer interface –

Magnetometer works on I2C interface. Greybot provides 2 pins PC0 (SDA), PC1 (SCL). It

provides orientation of a GreyBot. It reads 0-360 Degree values, so robot can calibrate its exact

orientation. It helps the user to localize the robot in space.

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6.5 Bluetooth Module Interface –

HC-05 Bluetooth module can be interfaced with GreyBot. That is used to communicate with

laptop, cellphone and other robots. User can test SWARM algorithm using this feature.

Bluetooth module is directly connected to UART section (PD0-RX, PD1-TX) of GreyBot.

Figure 8. GreyBot V1.0

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7. Contact Us At:

GreyRobotics

Mumbai, India.

Visit us at: www.greyrobotics.in

Mail us at: greyrobotics@gmail.com

For more updates connect with us:

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https://www.youtube.com/channel/UCAHPFIXMrRD0IOKjdPTFpnw

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