general information about arduino_1

8/22/2019 General Information About Arduino_1

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Written by Bicycle Adapted Generator Team with assistance from Arduino Forum

ContentsGeneral Information about Arduino ............................................................................................................. 2

Quick notes about important pins ............................................................................................................ 2

Connecting the Arduino to Computer: ..................................................................................................... 2

How to Change ADC sample rate .............................................................................................................. 4

Sensors used in the Bicycle Adapted Generator Project .......................................................................... 4

Temperature sensor .............................................................................................................................. 4

Voltage Sensor ...................................................................................................................................... 4

Current Sensor ...................................................................................................................................... 5

RPM sensor ........................................................................................................................................... 5

Sample code from Bicycle Adapted Generator Project with detailed comments .................................... 6

PLX-DAQ .................................................................................................................................................... 9

Steps to using PLX-DAQ....................................................................................................................... 11


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General Information about Arduino

Operating voltage 5V

Digital I/O pins 54 (15 provide PWM output)

Analog input pins 16DC current per I/O pin 40mA

DC current for 3.3V pin 50mA

Flash Memory 256Kb

ADC sample rate 9600Hz but can be changed (see below for details)

Baud rate Up to 1Mbps

Note: 9600Hz ADC sample rate suggest each analog read will take about 100us

Changing the ADC sample rate up to 77KHz does not significantly affect precision of the value.

Arduino Mega can be powered via the USB connection or with an external power supply. (7-12V batteryrecommended) If external power supply has to be used, connect to the power jack on the Arduino board

or through VIN pin.

Quick notes about important pins

5V pinArduino outputs a regulated 5V on this pin. It can be used as a voltage source for sensors. Do

not make a mistake of supplying 5V voltage to this pin. It will damage the board permanently

3V3 pin3.3V pin. Same functionality as 5V pin

GNDGround pin of the Arduino. This can be used by the sensors for gnd connection

IOREFreference voltage from Arduino. Supplies certain amount of voltage set by the microcontroller

(which is controllable by C code)

For more information, please visit the Arduino website.

Connecting the Arduino to Computer:

First step is to configure your computer to recognize the Arduino. If you connect the Arduino to the

computer and skip this step, the computer wont recognize the Arduino and you wont be able to upload

the code to the microcontroller

1. Install the Arduino environment from the Arduino website. (download the file and extract on

the C drive.)

2. Connect the board to the computer. PWR LED should light up

3. Wait for the windows to try and install driver for the Arduino. It will fail


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4. Go to device manager on your Windows (click on start icon and right click computer. Then click

properties. You will see general information about your computer and see few link tabs on the

left. Click on the device manager)

5. Look under ports (COM & LPT). You will see a port named Arduino Mega (COMxx)

6. Right clock the port and choose update driver software7. Choose the browse my computer for Driver software option and navigate to Drivers folder

located inside your Arduino environment (from step 1)

Above steps will allow the Arduino to be properly recognized by your computer. Next, you need to let

the Arduino environment know that you are using Arduino Mega (see below image)


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How to Change ADC sample rate

Normally, the sample rate of ADC is preset to 9600Hz. The calculation to get the pre-set value is as

follows:

ADC clock speed = 16MHz

Pre-scale factor = 128

16MHz / 128 = 125KHz (clock speed)

Conversion time (analog to digital) = 13 ADC clocks

Pre-set sample rate = 125KHz / 13 = 9600Hz

By changing the pre-scale factor, you can increase the ADC clock speed and sample rate up to 1MHz and

77KHz separately. It is advised not to go over the 1MHz limit because of precision problems. Below is a

code to change pre-scale factor (tested by one of the people on forum on ATMEGA chip)

// defines for setting and clearing register bits#ifndef cbi

#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))#endif#ifndef sbi#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))#endif

// set prescale to 16sbi(ADCSRA,ADPS2);cbi(ADCSRA,ADPS1);cbi(ADCSRA,ADPS0);

Sensors used in the Bicycle Adapted Generator Project

-

Temperature sensor (TMP36)- Voltage sensor (Phidgets 1135)

- Current sensor (Phidgets 1122)

- RPM sensor (IR LED and Phototransistor from Solarbotics)

Temperature sensor

The sensor output varies from 0-5V

The sensor output follows the formula shown below:

Temperature in Celsius = [(Vout in mV)500] / 10;

For example if the sensor output is 1V, that means (1000500) / 10 = 50 Celsius.

Voltage Sensor

Unlike other sensors used for this project, the specification sheet did not reveal the relationship

between sensor output voltage and its actual readings. The formula had to be calculated through

measurements and resources in the lab. (Steps shown below)


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1. Arduino readings range from 0 to 1024 (which corresponds to 0 to 5V). Voltage sensor reading

varies from -30 to 30V. When zero voltage was detected, Arduino read 512. The output of the

voltage sensor range from 0.5 to 4.5V. Small table shown below shows the relations ship

between these values

Arduino readings 102 512 922Voltage sensor

readings

-30 0 30

Voltage sensor output 0.5 2.5 4.5

2. By looking at above table, the relationship between voltage sensor reading and Arduino

readings can be seen. Calculation with small explanation is given below

Arduino reading of 922 -> refers to 30V on voltage sensor

Arduino reading of 512 -> refers to 0 V on voltage sensor

Assuming linear relationship (why shouldnt it be)

922512 = 410 units30 V / 410 = 0.073 volts per unit

Formula for voltage

(Arduino reading512) * 0.073 = Actual voltage measured by sensor

The formula above may change slightly for each sensor

Current Sensor

The current sensor formula wasnt provided and relationship between its output voltages to actual

sensor readings had to be figured out again using method in the voltage sensor section

Formula

Actual current measured by sensor = (Arduino reading - 512) * 0.074;

RPM sensor

A circuit consisting of IR emitting diode and phototransistor is used to calculate the rpm (shown below).

The idea was to detect the falling edge of the output. Normally, the output is kept at 0V until

interruption occurs between IR diode and phototransistor. The moment interruption is detected, the

output is pulled up to 5V until interruption disappears.


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Sample code from Bicycle Adapted Generator Project with detailed comments

Below is a sample code from Bicycle Adapted Generator (comments are shown in green or red)

Pay Special attention to the Red comment text about early initialization of the analog pin and how to

communicate properly with the PLX-DAQ program. (Further information about the PLX-DAQ described in

the next section)

int tspin = 0; //The variables declared here refer to pin number that Arduino will read from

int tspin_1 = 1; // for example tspin = 0 will read in information from analog pin 0 (shown later)

int tspin_2 = 2;

int current = 3;

int volt_read = 4;

int current_5 = 5;

int current_6 = 6;

int voltvalue = 0; // The variables decloased below are used for calculations. You do not have to declare

them here but I prefer to keep them in one place

float volt = 0;

int ampvalue = 0;

float amps = 0;

int ampvalue_5 = 0;

float amps_5 = 0;

int ampvalue_6 = 0;

float amps_6 = 0;

int reading_1 = 0;

int reading_2 = 0;

float aref_volt = 5; //reference voltage that Arduino will read the values in

float d_ratio = 1023.00; // resolution of the Arduino (12 bit resolution => 2^12)

float tot_data;

int ledPin = 13; // digital pin 13 will supply voltage to IR LED for rpm readings

volatile byte rpmcount;

unsigned int rpm;

unsigned long timeold;

void rpm_fun()

{

//function for generating rpm values. rpmcount refers to number of interruptions possible

rpmcount++;

}

void setup() //initialization of the arduino


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{

Serial.begin(9600);

//analogReference();//This is a code that can be used to increase the accuracy reading of arduino by

changing analog voltage reference (instead of 5/2^12 you can change this to 3.3 for 3.3/2^12)

attachInterrupt(0, rpm_fun, FALLING); // Function for detecting interrupt. Number 0 refers to digitalpin 2 of the arduino. Everytime falling edge is detected from digital pin 2, the function rpm_fun will run

//Turn on IR LED

pinMode(ledPin, OUTPUT);

digitalWrite(ledPin, HIGH);

rpmcount = 0;

rpm = 0;

timeold = 0;

Serial.println("CLEARDATA"); //Serial.println are modified to allow PLX-DAQ program to understand the

data coming off the Arduino

Serial.println("LABEL, ,rpm, temp, amps_1, volts_1, amps_2, amps_3"); //Column labels for each data

}

void loop()

{

detachInterrupt(0); // stop reading the interruption from digital pin 2

rpm = 31*1000/(millis() - timeold)*rpmcount; //formula to calculate rpm

timeold = millis();

rpmcount = 0;

attachInterrupt(0,rpm_fun,FALLING); //start reading the interruption

int reading = analogRead(tspin);

float voltage = reading * aref_volt;

voltage /= d_ratio;

float temperature = (voltage - 0.5)*100; //formula to calculate temperature

Serial.print("DATA,TIME,"); //initialize the recording of data in PLX-DAQ. Will record the data in each

column of excel separated by comma. Also will record time for each data measurement

Serial.print(rpm); Serial.print(","); //record rpm and move on to next column (comma)

Serial.print(temperature); Serial.print(",");

reading_1 = analogRead(tspin_1); // Initialize the analog pin to charge the sample and hold capacitor

early

delay(100);//Delay to allow charging of the capacitor

reading_1 = analogRead(tspin_1);

float voltage_1 = reading_1 * aref_volt;


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voltage_1 /= d_ratio;

float temperature_1 = (voltage_1 - 0.5) * 100;

reading_2 = analogRead(tspin_2);

delay(100);reading_2 = analogRead(tspin_2);

float voltage_2 = reading_2 * aref_volt;

voltage_2 /= d_ratio;

float temperature_2 = (voltage_2 - 0.5) * 100;

ampvalue = analogRead(current);

delay(100);

ampvalue = analogRead(current);

amps = (ampvalue - 509) * 0.074; //formula for calculating current

Serial.print(amps); Serial.print(",");

voltvalue = analogRead(volt_read);

delay(100);

voltvalue = analogRead(volt_read);

volt= (voltvalue - 570) * 0.0685; //formula for calculating voltage

Serial.print(volt); Serial.print(",");

ampvalue_5 = analogRead(current_5);

delay(100);


amps_5 = (ampvalue_5 - 511) * 0.074;

Serial.print(amps_5); Serial.print(",");


delay(100);


amps_6 = (ampvalue_6 - 511) * 0.074;

for(int k=0;k


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PLX-DAQ

The program PLX-DAQ (it is actually excel macro) is designed to receive data from the propeller

(microcontroller from company Parallax) and export the data into an excel spreadsheet.

Since it uses Serial transmission and USB cable to transfer data, I used this program and modified the

Arduino code slightly to let PLX-DAQ understand the data it receives from Arduino.

An example of the excel spread sheet using PLX-DAQ is shown below.(using some the sample code

above)

rpm amps_1 volts_1 amps_2 amps_3

5:13:12 65535.00 2.52 8.15 0.07 9.4

5:13:13 90.00 3.11 8.56 0.07 4.44

5:13:14 150.00 2.81 8.36 0.07 8.44

5:13:15 120.00 2.81 8.43 0.07 9.79

5:13:16 150.00 3.18 8.56 0.07 -0.75

5:13:17 120.00 2.74 9.25 0.07 3.915:13:18 120.00 2.89 8.63 0.07 9.8

5:13:19 120.00 3.03 8.43 0.07 8.55

5:13:20 150.00 2.89 8.77 0 1.09

5:13:21 150.00 3.03 9.11 0 8.46

5:13:22 150.00 2.96 9.32 0.07 2.63

5:13:23 150.00 3.26 8.84 0 6.76

5:13:24 150.00 3.18 8.77 0 8.14

5:13:25 180.00 3.03 8.84 0.07 9.58

5:13:26 150.00 3.03 8.84 0 7.31

5:13:27 150.00 2.96 9.18 0 8.99

5:13:28 180.00 2.89 9.11 0.07 9.96

5:13:29 150.00 2.81 9.32 0 6.96

5:13:30 180.00 3.11 9.11 0 6.19

5:13:31 150.00 2.89 9.45 0 7.06

5:13:32 150.00 3.11 9.32 0.07 6.56

5:13:33 150.00 2.81 8.77 0 11.7

5:13:34 120.00 3.11 9.18 0 5.08

5:13:35 150.00 3.26 9.38 0 4.73

5:13:36 150.00 2.96 9.45 0.07 5.92

5:13:37 150.00 2.89 9.73 0.07 11.24

5:13:38 180.00 3.18 8.97 0 7.22

5:13:39 150.00 3.18 9.38 0.07 7.3

5:13:40 180.00 3.18 9.86 0 2.96

5:13:41 150.00 3.4 9.73 0 4.98

5:13:42 180.00 3.33 10 0 5.38

5:13:43 150.00 3.11 9.8 0.07 4.66

5:13:44 150.00 3.18 10 0.07 4.52

5:13:45 150.00 3.03 9.86 0 3

5:13:47 150.00 3.33 9.66 0 -1.62

5:13:48 180.00 3.18 9.66 0 9.81

5:13:49 120.00 3.18 9.93 0 2.55


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5:13:50 150.00 3.48 10.55 0.07 3.57

5:13:51 180.00 3.33 11.23 0 1.16

5:13:52 150.00 3.63 10.75 0.07 5.37

5:13:53 150.00 3.7 10.82 0 1.1

5:13:54 180.00 3.4 10.96 0 2.49

5:13:55 180.00 3.4 11.85 0 4.72

5:13:56 150.00 3.26 11.3 0.07 2.66

5:13:57 150.00 3.33 12.4 0.07 -1.18

5:13:58 150.00 3.4 11.03 0 8.98

5:13:59 120.00 4.07 11.37 0 4.99

5:14:00 150.00 3.85 12.95 0 0.46

5:14:01 120.00 3.18 11.44 0 8.99

5:14:02 120.00 3.7 11.85 0.07 7.93

5:14:03 150.00 3.85 10.82 0.07 4.78

5:14:04 150.00 3.7 13.43 0.07 0.36

5:14:05 120.00 3.85 13.01 0.07 -1.21

5:14:06 150.00 3.7 12.47 0 2.03

5:14:07 150.00 3.7 11.03 0.07 5.56

5:14:08 120.00 4 12.74 0 0.42

5:14:09 120.00 3.33 13.01 0.07 2.94

5:14:10 150.00 3.85 12.6 0.07 0.48

5:14:11 150.00 3.77 12.47 0.07 1.03

5:14:12 150.00 3.92 11.99 0 3.13

5:14:13 150.00 3.7 12.26 0 2.6

5:14:14 150.00 4 12.26 0 2.7

5:14:15 120.00 4.14 11.51 0.07 1.33

5:14:16 150.00 4.22 12.67 0 -1.07

5:14:17 150.00 4.14 13.08 0 3.72

5:14:18 120.00 3.48 13.49 0 1.155:14:19 180.00 3.92 13.29 0 0.18

5:14:20 120.00 3.55 11.44 0.07 6.72

5:14:21 120.00 4.29 12.74 0 -0.73

5:14:22 150.00 3.85 13.01 0 1.57

5:14:23 120.00 3.77 9.8 0 -0.21

5:14:24 120.00 2.96 13.36 0.15 2.53

5:14:25 90.00 4 11.85 0 -0.8

5:14:26 120.00 3.03 10.96 0.07 5.06

5:14:27 90.00 3.26 13.36 0 -1.58

5:14:28 120.00 2.74 7.47 0 -2.33

5:14:29 60.00 3.4 8.7 0.07 0.38

5:14:30 120.00 2.59 12.33 0 3.7

5:14:31 90.00 4.14 12.74 0 -2.37

5:14:32 120.00 2.52 8.97 0 4.2

5:14:33 120.00 2.22 7.74 0.07 0.05

5:14:34 60.00 2.52 9.86 0 0.24

5:14:35 90.00 3.77 11.03 0 -1.2

5:14:36 120.00 2.81 7.33 0.07 0.16

5:14:37 90.00 2.44 9.93 0 0.61


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5:14:38 90.00 3.03 12.6 0 -0.04

5:14:39 120.00 3.4 9.8 0 0.47

5:14:40 90.00 3.26 13.15 0.07 -0.49

5:14:41 120.00 3.92 10.21 0.07 -0.13

5:14:42 120.00 2.07 6.78 0 -1.76

5:14:43 60.00 2.96 11.3 0 0.73

5:14:44 120.00 4 12.12 0 -0.7

5:14:45 90.00 2.29 6.37 0.07 -2.51

5:14:46 90.00 3.48 8.29 0 0.05

5:14:47 90.00 2.66 11.71 0.07 2.12

5:14:48 120.00 4 12.4 0 -2.11

5:14:49 90.00 2.96 7.67 0 -0.15

5:14:50 90.00 2.29 8.36 0 1.29

5:14:51 90.00 3.7 13.15 0.07 -0.35

5:14:52 120.00 3.18 8.22 0 0.68

5:14:53 120.00 2 8.84 0 3.1

5:14:54 90.00 3.92 12.54 0 -1.94

5:14:55 90.00 3.92 10.55 0.07 -2.13

5:14:56 90.00 3.26 7.88 -0.07 0.15

5:14:57 120.00 2.59 11.44 0 0.67

5:14:58 90.00 4 12.26 0 -0.61

5:14:59 90.00 2.96 7.67 0.07 0.65

5:15:00 120.00 3.4 13.01 0 -0.89

5:15:01 90.00 3.77 10.14 0 -1.12

5:15:02 120.00 2.96 11.92 0 3.69

5:15:03 120.00 4 12.47 0 -0.4

5:15:04 90.00 2.81 8.36 0.07 0.58

5:15:06 120.00 3.77 13.56 0 -1.1

5:15:07 90.00 3.26 8.08 0.07 -0.255:15:08 120.00 2.81 10.75 0 5.45

5:15:09 120.00 3.85 11.23 0 -0.68

5:15:10 90.00 3.03 7.81 0 2.76

5:15:11 120.00 3.77 13.22 0 -1.35

5:15:12 90.00 3.55 9.8 0.07 0.51

5:15:13 120.00 3.7 12.95 0 -2.3

5:15:14 120.00 3.85 9.52 0.07 0.67

5:15:15 120.00 2.89 12.54 0.07 2.48

5:15:16 120.00 3.48 8.01 0 -0.06

5:15:17 30.00 0 -11.17 0 -0.03

Steps to using PLX-DAQ

1. Install the PLX-DAQ program (from the internet or from the attached files)

2. Run the PLX-DAQ from the start menu and allow the macro to run in the excel spread sheet

3. If all is well, you will see a screen similar to image below


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4. Simply click connect (pay attention to baud rate shown on the settings above and from the

Arduino which is declared using Serial.begin(9600) code in the setup section. Make sure these

two are equal)

5. If the Arduino code is set up correctly, you should see the data being recorded every second.

Please refer to red comment text in the sample code for more information about

communication between PLX-DAQ and Arduino.

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