electronics design laboratory lecture #8ecee.colorado.edu/ecen2270/lectures/lecture08.pdf• either...

Electronics Design LaboratoryLecture #8

ECEN 2270 1Electronics Design Laboratory

Notes• Starting Experiment 4 this week – “Robot Speed and Position Control”• This lab requires you to have BOTH wheels running by the Lab 4 demo

date• Tuesday this week

– Turn in prelab 4.A and complete 4.A

– Redo Labs 2B and 3 on the second wheel

• Thursday this week: – Have speed control working on both wheels

– Start 4.B: connecting Arduino microcontroller board to your speed control circuitry and coding the microcontroller

• Lab 4 demo is Thursday the week after (see Lab calendar)

Electronics Design Laboratory 2ECEN 2270


Speed Sensor and Filter

GND

5VDC

0-5V Speed Output proportional to actual motor speed

Vspeed

ForwardController

Reverse Controller

0-10V

0-10V

0-5V Speed Output proportional to desired motor speed

+-Speed errorForward

NOT Forward

Experiment 1 & 2

Experiment 3a

Experiment 3b

Experiment 4

Board Layout


GND GND GND GND 10V10V5V5V

GND 10V

10VGND

5V Linear Regulator

Speed Control (2 per wheel)Speed Sensor

(1 per wheel)

Encoder 1Encoder 2

PWM 1 Vref 1PWM 2 Vref 2

CWCC

10VGND

10VGND

B1 - LeftB2 - Left

B1 - RightB2 - Right

DC1DC2

DC1DC2

10VGND

5VGND5V

Encoder 1 PowerEncoder 2 Power

10V from power supply

5V Generated by Arduino


Arduino Power System

VIN

5V3.3V

PWRIN

USBVCC

• Three power inputs: USB (provides 5VDC), VIN pin (7-12VDC) and a barrel jack (9-12VDC)

Outputs, generated by Arduino onboard power system

7-12V, External Supply. Bench-top, batteries, etc.

9-12V, Center Positive Barrel Jack

USB 5V. Up to 500mA

5V D-

D+GND


Arduino Power System

PWRIN

GND

5V

Linear Regulator

47uF 47uF 100nF

GND

3.3V

10kΩ

10kΩ

Linear Regulator

1uF

3.3V

LP2985-33DBVR5V

GND100nF

5V

• Need to select which power input to use, and generate 5VDC and 3.3VDC

Decoupling Capacitors

3.3V Linear Regulator

5V Linear Regulator

MC33269D-5.0

VIN

PWRINUSBVCC

VIN

VINUSBVCC

Max(VIN,PWRIN)

High if VIN or PWRIN is supplied

Either USBVCC or 5V

uC power


+ -

Motor Drivers

Encoders

5VDC

10VDC

Arduino Power System• Either batteries or a DC Power Supply

will generate 10VDC, which we will connect to the VIN pin.

• Make sure to use decoupling capacitors on the 10VDC line.

• Not using decoupling caps will waste a bunch of your time since motors are noisy and may cause trouble for your microcontroller if the power supply is not clean.

Arduino UNO Systems


USB-B port

ATmega328P 8-bit uC

ATmega8u2 USB To Serial

Clock Generator

Status LEDsDigital IO(GPIO)

Reset Button

Analog IO

16MHz Clock

Power System

• The Arduino is built around an 8-bit microcontroller• Communication with the ATmega328P is achieved through a USB interface• Since the ATmega328P does not ‘talk’ USB, a serial to USB conversion must be made

Arduino UNO Systems


ATmega328P 8-bit uC

ATmega8u2 USB To Serial

Power System

• The Arduino is built around an 8-bit microcontroller• Communication with the ATmega328P is achieved through a USB interface• Since the ATmega328P does not ‘talk’ USB, a serial to USB conversion must be made

Digital Inputs/Outputs: GPIO


ATm

ega3

28P

8-bi

t uCGPIO: General Purpose Inputs/Outputs. These are digital

outputs, so only voltages of 0V or 5V may be generated. Pins marked with (~) may be used to output PWM signals. Maximum current of 40mA per output. Pins default to Inputs

100MΩ

5V

GPOIX5V

{0,1}

5V

RA

RB

{0,1}

{0V,5V}0V-5V

20kΩ

PULLUP

INPUT/OUTPUT

5V

Internal ATmega328P Hardware

digitalRead(GPIOX)

digitalWrite(GPIOX,{HIGH,LOW})

pinMode(GPIOX,mode)

Program Code

Digital Inputs/Outputs: GPIO


ATm

ega3

28P

8-bi

t uCGPIO: General Purpose Inputs/Outputs. These are digital

outputs, so only voltages of 0V or 5V may be generated. Pins marked with (~) may be used to output PWM signals. Maximum current of 40mA per output. Pins default to Inputs

As Digital Outputs…

5V0V

digitalRead(GPIOX) returns 1digitalRead(GPIOX) returns 0

digitalRead(GPIOX) returns 1VGPIOX

t

5V0V

VGPIOX

tdigitalWrite(GPIOX,HIGH)

digitalWrite(GPIOX,LOW)digitalWrite(GPIOX,HIGH)

As Digital Inputs…

As PWM Outputs… analogWrite(GPIOX,duty_cycle)

=

PWM

on

Tt255Integerduty_cycle

t

5V0V

VGPIOXTPWM

(duty_cycle/255)*TPWM

Analog Inputs


ATm

ega3

28P

8-bi

t uC Analog Inputs: 6 Analog inputs are available. These pins

convert an analog voltage in the range 0V-AREF to an integer in the range 0-1023. The value read by the ATmega328 can be calculated as:

Analog reference AREF defaults to 5V. It takes approximately 100 µs to preform an analog read. Analog inputs A0-A5 can be configured to act exactly like the GPIO pins if needed.

( )

= 1023IntegerVALX

AREFVA

AX 0V-5V

EXTERNAL 5V

ADCIN

REFAREFOUT 0-1023

Internal ATmega328P Hardware Program Code

analogRead(AX)

analogReference(mode)

Analog Inputs


ATm

ega3

28P

8-bi

t uC Analog Inputs: 6 Analog inputs are available. These pins

convert an analog voltage in the range 0V-AREF to an integer in the range 0-1023. The value read by the ATmega328 can be calculated as:

Analog reference AREF defaults to 5V. It takes approximately 100 µs to preform an analog read. Analog inputs A0-A5 can be configured to act exactly like the GPIO pins if needed.

( )

= 1023IntegerVALX

AREFVA

5V

0VSample 1 Sample 2 Sample 3

Sample 1: 2.6VSample 2: 2.7VSample 3: 1.3V

analogRead(AX) returns

VAX

=

=

1023

0.56.210236.2IntegerVV

AREFV

analogRead(AX) returns 552 analogRead(AX) returns 266

531

As Analog Inputs…

Robot Control with the Arduino


GPIO: General Purpose Inputs/Outputs. These are digital outputs, so only voltages of 0V or 5V may be generated. Pins marked with (~) may be used to output PWM signals. Maximum current of 40mA per output. Pins default to Inputs

Analog Inputs: 6 Analog inputs are available. These pins convert an analog voltage in the range 0V-AREF to an integer in the range 0-1023

( )

= 1023IntegerVALX

AREFVA

USB input used for programming and

debugging

Power system connected as seen previously

• Outputs to robot: Stop/Go controls (2 per wheel) Speed reference (1 or 2 total)• Voltages: 5VDC for speed sensing circuits and 10VDC for Motors/Encoders• Inputs from robot: On/Off and Encoder Pulses

ATm

ega3

28P

8-bi

t uC

Robot Control with the Arduino


ATm

ega3

28P

8-bi

t uC

10VGND5V

ENCODER_L( 2)ENCODER_R( 3)

ON/OFF( 6)CW_L( 7)CC_L( 8)

REF_L( 9)

REF_R(10)CW_R(11)CC_R(12)

LED(13)

Input from bench supply or battery

Output used to supply +5V circuitry (Labs 2 and 3)

• Outputs to robot: Stop/Go controls (2 per wheel) Speed reference (1 or 2 total)• Voltages: 5VDC for speed sensing circuits and 10VDC for Motors/Encoders• Inputs from robot: On/Off and Encoder Pulses

Programming• Plug-in USB cable• First-time use only:

install USB driver (if need be)

• Start Arduinodevelopment environment

• Open an example: File Examples1.Basics Blink

• Click Upload• http://arduino.cc

Extensive on-line reference, examples, blog, forum, …


“Blink” example


/*BlinkTurns on an LED on for one second, then off for one second, repeatedly.

*/

void setup() {// initialize the digital pin as an output.// Pin 13 has an LED connected on most Arduino boards:pinMode(13, OUTPUT);

}

void loop() {digitalWrite(13, HIGH); // set the LED ondelay(1000); // wait for a seconddigitalWrite(13, LOW); // set the LED offdelay(1000); // wait for a second

}

Commands in setup are executed only once, at the beginning

Commands in loop are executed repeatedly

Speed Control Setup for One Wheel


Pin 7

Pin 8Pin 9

Pin 6 ON/OFF switch

Power supplies:+10V from bench power supply (or from battery)+5V from Arduino board

+5 V

1K

1K

1K

ON

OFF

o1

o2

Speed control code example


/*ECEN2270 motor speed control example (left wheel only)*/

// define pinsconst int pinON = 6; // connect pin 6 to ON/OFF switch, active HIGHconst int pinCW_Left = 7; // connect pin 7 to clock-wise PMOS gateconst int pinCC_Left = 8; // connect pin 8 to counter-clock-wise PMOS gateconst int pinSpeed_Left = 9; // connect pin 9 to speed reference

// setup pins and initial valuesvoid setup() {

pinMode(pinON,INPUT);pinMode(pinCW_Left,OUTPUT);pinMode(pinCC_Left,OUTPUT);pinMode(pinSpeed_Left,OUTPUT);pinMode(13,OUTPUT); // on-board LEDdigitalWrite(pinCW_Left,LOW); // stop clockwisedigitalWrite(pinCC_Left,LOW); // stop counter-clockwiseanalogWrite(pinSpeed_Left,100); // set speed reference, duty-cycle = 100/255

}

void loop() {digitalWrite(13,LOW); // turn LED offdo {} while (digitalRead(pinON) == LOW); // wait for ON switchdigitalWrite(13,HIGH); // turn LED ondelay(1000); // wait 1 seconddigitalWrite(pinCW_Left,HIGH); // go clockwisedelay(3000); // for 3 secondsdigitalWrite(pinCW_Left,LOW); // stop

}

Lab 4 Part A• Clean up Lab 3 circuit, make sure you have a speed sensor

and two feedback controllers for both wheels• Play with the Arduino. Test the Blink program, and run any

other test programs that look interesting• At the end of part A, you should be able to use the Arduino

for speed control of both wheels• Make sure you know which direction the wheels will spin!


electronics design laboratory lecture #8ecee.colorado.edu/ecen2270/lectures/lecture08.pdf• either...

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