Experience with the new PI-2 

In this post i will share about my initial experience about PI-2,the latest model of Pi-family. Pi is really evolving and getting better with the time. Here are my experiences and observations.
1.BOOT TIME
The first difference you will find when you will make the Pi2 boot is there are 4 raspberries on the top of screen instead of 1 raspberry on B+ representing the quardcore nature of the processor. The time taken by Pi 2 to boot is significantly lesser than the B+.

2. NOOBS
If you have an older version of NOOBS you need to update it to run it on Pi2 since the ARM architecture is different on the two boards.The new version of NOOBS is compatible with the B+ model and the Pi2. However the new Noobs have very few operating systems to select from. Future releases will definitely and should definitely have more options.
However i had a queer observation i ran the new noobs on B+ and on Pi2 using the same SD card. When i run it on Pi2 and boot into the desktop i get the following message on screen.
GDBus.Error.org.feedesktop.Policykit1.Error.Failed: Cannot determine user of subject. Apart from this the operating system works fine.

3. RESOLUTION
since there is no bios on the Pi there is pain in getting the resolution right.The GPU reads the config.txt file everytime it boots up. I connected my Pi on a LG LED TV.And when i swap the Pi2 and B+ keeping the same SD card resolutions get disturbed. Had to fix it time and again if you also have such problem it can be fixed by firing Sudo nano/boot/config.txt. in the LX terminal . Paste the config.txt in your SD card if it is not there ,the file can be found on the raspberry pi official website. You will need to change a few values.
4. GAMES AND APPLICATIONS
I ran minecraft and the game play is much smoother on the Pi 2. Also the game loads faster. Similarly mathematica loads much earlier on Pi2. I also found the webpages load much better on PI

5. VIDEOS
Ran the sample video by using omxplayer /opt/vc/scr/hello_pi/hello_video/test.h264. The video runs great on both. Also ran a movie "book_of _life". To put the movie on pi i first put the file on the pendrive connected it to pi ,from the pendrive i copied it to the desktop.Changed the directory using cd/home/pi/Desktop. Then used omxplayer -o local book_of _life.mp3 to play it and have the audio through the 3.5 mm jack.I couldn't see any difference in the video playback on both the pi.

I have also done a video about the Pi ecosystem and comparison of the two Pi boards i used. I have made the video with the view that anybody who is not familiar with the Pi is able to have a understanding of what it is and for those who are already familiar with it i have info about the new things we are likely to see in the Pi ecosystem. Hope you will enjoy the video.





WHAT I DON'T LIKE ABOUT PI :


1. while booting the pi. The pi asks for username and password. After you enter the user name as Pi and then when you will try to enter the password you will see nothing appearing on the screen when you will press the keys on you keyboard.But actually if you have faith in yourself and you type raspberry and then if you will press enter you will find that you have successfully logged in. There should be stars****** on key press.


2. Pi doesn't have a power on /off button. Usually most of us connect our pi's adapter to a multisocket board but it is annoying to turn it off from there. It would be great if there is a button on pi to do this. Till it gets there on the board there is another solution for the people like me ,there comes a used cable that has a on/off button which can be used to as an alternate.


ABOUT THE PERIPHERALS I USED:

• I used a wireless keyboard and mouse for the first time,earlier i use to go with a wired one. For those who want to buy one ,Logitech MK220 works flawless on the pi,no hassel just plug and play. Moreover this is the cheapest one available right now.

• For wireless connectivity i used EDUP Mini Wireless N 11n Wi-Fi Nano USB Adapter. This is also just plug and play.

• One last thing, do use a good quality power adapter otherwise it might deter the quality of your experience,the B+ and pi2 has good brown out detection and the power LED blinks if there is not enough power available.

Processing:

What is there in the Processing software? 

Processing is a language and a development environment which came into existance in 2001.It is created by Ben fry and  Casey Reas at MIT media labs It is open and free to download development environment that can run on windows,linux and Mac.It is used by artists,designers,researchers and hobbists to create amazing visual arts and softwares.  

It has something for everyone no matter which domain of programming you fall into,if you are a android developer you can develop apps on it,if you work with core java you will find that in this too,similarly if you work in python there is also a python mode which has been added recently.Similarly if you want to work with OpenCV or want to create web servers or want to play with audio files or create GUI and interect with hardware like arduino or kinect,it has it all. whats brillient about this language is it has its own syntax and style but also gives you ability to make use of methods of some other specific domains like javascript,java,scala,actionscript, python,android, etc

Many people don't know but  Arduino IDE has come out from processing. Thats why there is a striking similarity between the two IDE.

This is one of the most versatile software environment that i have seen so far. It also gives you the ability to export your source code as an application that can run on  Linux,Windows and Mac. This is a great feature for creating applications for an end user.

Downloading and installing  Processing:

Processing is free to download. You can download it for your operating system from the following link download processing

After you download the zip file you will need to extract it. After you extact it you will find a folder that that will have the following content

You need not wait for any installation process to occur just double click on the processing icon and you are ready to write your first program.

When you will run it for the firsttime. It will create a procesing folder in your Libraries/Documents on a windows machine. 

Your source codes are called sketches in processing and all your source codes will be saved in a folder within  this folder . The name of the subfolder will be same as that of your source code.

Now you are all set  to write your first code.

Example: Replicating a graphics in processing

I have a picture that i will replicate with a processing code. The picture is as below and is taken from  http://www.clker.com/clipart-25665.html

// This code is written by Deepankar Maithani
//IMPORTANT
//The top left corner of the processing window is considered as (0,0) coordinate all the coordinate values are set with respect to that.

void setup()
{
size(600,600); // size of processing window  
background(255);// set color of background to white
noFill();// upcoming figures will only have boundries
strokeWeight(10); // width of boundries
  
  ellipse(150,300,150,150);//back tyre
  ellipse(150,300,30,30);// back smaller inner circle
  ellipse(390,300,150,150);//Front tyre
  ellipse(390,300,20,20);//front smaller inner circle
  ellipse(260,320,50,50);// paddle axle
  
  arc(150, 300, 180, 180, 4.1015, 5.8468, OPEN);// back mudguard
  arc(390, 300, 185, 185, 4.1887, 5.8468, OPEN);// front mudguard
  line(235,262,340,220);// connecting line back to front mudguard
strokeWeight(10.0);width graphics
strokeJoin(ROUND);// the characteristic  of join 
beginShape();
vertex(150, 285);// chain upper part. 
vertex(260,295);// 
endShape();

line(260,345,150,315);//chain lower part. done without  the vertex
strokeWeight(10);
  beginShape();
vertex(390, 290);// draws handle bar
vertex(320,150);
vertex(300,165);
vertex(280,160);
endShape();
line(250,250,220,200);
beginShape();// draws rider's seat
vertex(195,200);
vertex(240,200);
vertex(190,180);
vertex(195,198);
endShape();

}

void draw()
{
  
  // empty cause it is just a static graphics
  
}

NOTE: use ellipse command to draw the back tyre if you want exactly the same picture i like it this way

OUTPUT

Example 2 Displaying Sensor Value from arduino in Processing Window

Arduino Code: Upload this code to Arduino board

//This code written by Deepankar Maithani
const int  pot=A0;// Connect the middle pin of pot to this pin
int reading;// variable for storing the pot values
void setup() 
{
//initialize serial communications at a 9600 baud rate
Serial.begin(9600);
}
void loop()
{
reading=analogRead(pot);// reading the analog value
Serial.println(reading);// printing it on serial this line sends the data to processing
delay(1000);// stop for 1s
}

Processing Code:

// This software is written by Deepankar Maithani

import processing.serial.*; // this library handles the serial talk 

Serial myPort;  // Create object from Serial class
String data="" ; // empty string to gather the pot values
PFont  myFont;  // object from the font class
void setup()// this runs just once
{
size(500,500); // size of processing window
background(0);// setting background color to black
myPort = new Serial(this, "COM12", 9600);// giving parameters to object of serial class,put the com to which your arduino is connected and the baud rate
myPort.bufferUntil('\n');// gathers data till new line character
myFont=loadFont("Arial-Black-48.vlw");// font type see the data folder of your sketch
textFont(myFont,70);// font size


}
void draw()
{
  background(0);//refreshing background everytime the draw runs
  textAlign(CENTER);// alighn text to the centre of coordinates
  fill(255);// fill white color to text
  text(data,350,155);// display the data at 350,155 coordinate
  textSize(40);// size of text
  fill(#4B5DCE);// fillinf blue color on the text 
  text("Pot. Reading",155,150);
   noFill();the upcoming rect will not have anything inside
   stroke(#4B5DCE);// color of boader of rectangle
   rect(5,100,400,80); rectangle
  
}
void serialEvent(Serial myPort)// whenever serial event happens it runs
{
  
  data=myPort.readStringUntil('\n'); gathering data from pot in a variable
}

Demo of above softwares in action

For more info about the methods and API you can visit processing website orProcessing forum

Arduino to Processing by Deepankar Maithani is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Product Ergonomics

Ergonomics is a discipline that deals with the understanding of interactions among humans and other elements of  a system,this discipline plays an important role in enriching the  end user experience  of a product.  For the success of any product it is very important that the user finds your product easy to use,aesthetically pleasing and safe. when we see anything around us our brain makes a decision about how safe it is how appealing it is depending upon our earlier experiences and number of other factors.

Ergonomics is divided into three categories 1. Physical Ergonomics 2. Cognitive Ergonomics & 3 Organisational Ergonomics.I will focus on the earlier two categories in this post.

Physical Ergonomics deals with the Human body's response to the physical and physiological loads while the cognitive ergonomics makes sure that any system comply with the human cognitive strengths like we can't see too small texts  and should avoid our cognitive weakness whereever it will hinder the good interaction between the system and humans. For example on a mobile phone the size of the keys of dialler should be large enough for comfortable pressing of keys,the colour of font should be such that it is easy to read. sometimes our weakness is used as a benefit like the phenomenon of persistence of vision is used to create a moving picture.

Here i will share about this important aspect of product design process . There are many physical design features that are there on a product, reason for the existence of some of them are very easy to interpret logically while others need a more investigative  and through understanding. Below are some of the examples from our day to day life products to understand the importance.

1. Bucket design

Below is a picture of two buckets that i took long back in my house. The water caring capacity of both of them is same. But the designers of the one on the left have made some extra curves and that has added extra value  to the product by increasing the ease of use of the product. If you would try to lift a bucket full of water  and pour water in another container these curves will assist you to have a better grip and reduce the chances of spilling the water.

2. Laptop Keys

The picture below is of  a laptop keyboard. If you look at the key 'F' and 'J' closely you will find that there is a dash/hyphen embossed on these keys.This is found on every keypad. The reason for this is that when you get pro at typing you don't look at the keys while typing rather you look at the screen this row of keys  is the home row,these protruding/embossed  hyphon helps in giving you an idea about the position of your fingers on the keyboard with actually moving your eys off the screen by just the fel of touch.

3. Colour of  Bag's Interior

The bag shown below is a SLR camera backback. If you see it closely you will find that the fabric used to make the interior of the  bag at the right is a bright orange colour and this colour is used because most of the camera accessories are black in colour so if you drop say a memory card in the bag it would be very easy to find it in the contrasting orange background.. While  the bag on the left is black from inside so if you accidental drop your SDcard it would be hard to find it and a more vigilant  search would be required.

4. Antimicrobial properties of copper

Copper is known to have antimicrobial properties and thus restricts the growth of microbes on its surface ,keeping this property in mind and keeping in mind that copper is a fairly expensive metal it is used at specific locations on products used in hospitals to help stop infections spread. Infact this property of copper is put to use Indian houses  from years. You would easily find people keeping  drinking water  in copper utensils. You can read more here

4 Engine Fins

The engine of a motor bike specially the air-cooled engines have fins on it. Adding these fins would increase the amount of material required in manufacturing the engine but still they are added so that the surface area of engine can be increased and hence better heat dissipation is achieved resulting in better performance of engine

5. Train Wheels

The wheels of trains are a part of cone (technically called frustum) rather than being a cut out part of cylinder because this helps in reducing the hunting oscillations (sidewise oscillation) which would make the train ride uncomfortable.

So these examples perfectly explains that the  physical features of body of a product,the curves,the bends and the material plays a great role in the better interaction of product and humans. 

Product ergonomics by Deepankar Maithani is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Constant current LED driver

LEDs have become ubiquitous these days you can find them in different roles like being used as indicators, home and office lightning solutions, in music synced lightening systems at clubs, signboards  etc. Today i will share about a constant current driving circuitry to make some LEDs glow with DC power sources.

Why do we need a driver circuit?

The first thing that might come to your mind is why do we need a driver circuit when you can just simply connect a coin cell battery to make an LED glow and  for higher voltage sources you can easily drop the voltage to desired value by using a resistor.

The use of a dedicated circuit is necessary because using the above mentioned method won’t provide a consistent and robust solution. The current through the LED is sensitive to even small changes in voltage across the LED and the temperature of LED so using the above mentioned way may provide different LED performance in different environmental conditions. The inefficiency using a resistor to drop the voltage would even be magnified while driving a high wattage LED.

Constant current LED circuit built around IRFZ44

The circuit below shows a reliable way of lighting an LED. This circuit allows us to decide a particular value of current that will flow through the LED by adjusting the value of R2 resistor.Depending upon how much current is allowed to pass through the LED the intensity of LED is adjusted.

How does the Circuit works and deciding the values of  current setting resistance?

when the value of current flowing through the LED to the R2 becomes high enough to provide a drop of 0.7 V across the base emitter junction of the transistor the diode gets turned on and the extra current goes to ground through the diode. This feedback mechanism leads to a constant current flowing through the LED.

Deciding the value of  R2

Value of current through the LED = 0.5/R2

value of power dissipated across =0.25/R2

R1 hould be a high value quater watt resistance say 100k.

Benefits of using this circuit

• consistent LED performance over large range of supply voltage
• low dropout ie the output voltage can be just 0.6 volt higher than the input voltage
• cheap circuit

Important Points

• Because the transistor T1 is thermal sensitive the current set point is also thermal sensitive so choosing a transistor with low thermal senstivity will give more accurate results like 2N5088BU
• Care should be taken that the power dissipated by Q1 is within the range specified in data sheet power = voltage across Q1 x current through the LED
• For maximum efficiency the LED should be configured such that the voltage is near the supply voltage.

Constant current LED driver by Deepankar Maithani is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The Journey of Electronic Products from idea to customer's hand

It require interdisciplinary expertise to bring an idea from concept to life. There is a need to bring people with background as diverse intellectual background like manufacturing,design,core electronics, management   together and work together. To survive in today's competitive market you have to give a feature rich product to your customer and that too at lowest possible price. In today's era of globalisation the markets are now open for everyone and while this leads to opportunity to serve more customers it also poses the difficulty of surviving the competitive market. One of the strategy that the companies adopt is to accomplish different parts like say the software from firms in India and for manufacturing needs get the job done in china and this way the price of the final product comes down.

Below is a block diagram representation of Product design cycle:

The process starts with an IDEA that may be a completely new product idea or an improvement or enhancement to the existing idea. After this a comprehensive research is carried out to determine the feasibility of the idea and decisions like which existing technology is to be used out of the pool of technologies is made. Sometimes a product is practically feasibly by one technology and is not with another or out of the two technology one provides same performance but cheaper final product so every care should be taken during this phase because this is going to be the basis of product performance.

Once the research phase is over and you come out with a circuit that you are going to use to implement the feature  the prototyping is done,you take into account the erogonomics of the products and refine the look and feel of the product and then multiple design reviews are done to make sure everything is working as it should be,once the performance of product is satisfactory here, the next step is to analyse the manufacturing capabilities and things like what processes needs to be outsources what can be one in-house are decided,then documentation is created these includes the documents supplied to the user as user guides and the directions and information to be provided to the customer support people. 

Agency compliance ensure that the company followed all the rules and regulation like the environmental regulations and safety measures are taken. Agency compliance is another major step and sometimes it pose to be a hurdle and cause of delay of product release  one very recent example that i came across is the delay in the release of  official touch screen for raspberry pi due to the compliance.  There are FCC agency compliance for America and CE for the European countries and you need to have a compliance certificate to sell your product in these countries. 

After all this you bring the product to market, and right marketing of the product is very important these days. If you look around yourself you will easily find many examples of some innovative and out of the box marketing strategies that the companies are adopting.  There is great craze among people for some products like a new iphone launch and samsung's galaxyS4 . People stand in queue for whole night to get hold of the first phone. Samsung   introduced the concept of virtual queue when it launched the S4 where the customers were turned into marketers. Rather than physically standing in queue to get the phone an on-line queue was made and the more you tweet and comment about the product the more you will move ahead in the queue. 

Finally after the product is sold you need to give good customer service so that you make sure the customer is happy with your product. 

The Journey of Electronic Products from idea to customer's hand by Deepankar Maithani is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Arduino Tips & Tricks

Interfacing Gas Sensors with Arduino

Gas sensors commonly available in the market are the MQ series gas sensors. Different sensors in this series have different target gases for detection.But they all have more or less same structure and parts.Every gas sensor has a  heating coil and a surface with coating of some compound which is sensitive to the presence of a target gas.

Below is the picture depicting the structure of  MQ-2 which is a combustible gas sensor.

 These sensors require a 5V supply to power the heating coil .Since there is no electronic circuit inside them they can also be powered up using the AC.  These sensors can draw current upto 130 to 150 mA so these shouldnot be powerd using the Arduino. In case of the MQ-2 the sensitive material used in detection is Tinoxide. Mq2 is sensitive to LPG propane and Hydrogen.Below is a table with different gas sensors and their target gas.

CONNECTIONS WITH ARDUINO

As always now we will interface the sensor with the arduino Uno. The picture below shows the pins and how to connect it.

The polarity is not important in this sensor connect any one of the H pin to ground and the other one to the VCC. 

The MQ-2 sensor is not breadboard friendly,also it is difficult to solder wire directly on pins,I have designed a board on eagle to ease this out. I have also incorporated a LM35 temperature sensor.If you want to read out it interfacing you can read my previous post here

You can find the design files and gerbers on my github repository here Board,Gerbers. As always free to use and remix

SOURCE CODE:

float temp;
int gas;
int tempPin = A0;
int gasPin=A1;

void setup()
{
  Serial.begin(9600);
  
}

void loop()
{
  temp = analogRead(tempPin);
  gas=analogRead(gasPin);
  temp = temp * 0.48828;
  Serial.print("Temperature=")
  Serial.print(temp);
  Serial.print(',');
  Serial.print("Gas Sensor output")// 
  Serial.print(gas);// Stable readings comeout after 2 3 minutes
  delay(1000);

}

CALIBRATION:

The real challenge in dealing with the Gas sensors is the calibration,if you just want to use the gas sensor to know between high concentration of gas and low concentration  and then do something based on this ,for this much whatever we have seen so far is sufficient enough. But when you precisely want to know that what ppm of gas is there it is very important to correctly calibrate the sensor. For MQ2 it is recommended to expose the sensor to know value of target gas say 1000ppm and then observe the output and then with this data an algorithm is made to calculate the exact concentration of gas. But the problem is how to create an environment with known value of a gas. This would require a Lab with all the necessary equipments.

There are other factors that may also impact the sensor reading like humidity and temperature. Also there is a concept of burn in time which says that the sensor should be made to run for  of 18 to 24 hours after which it starts giving reliable readings. 

Quick Tip: In case you make the ADC to work with external reference or internal reference of 1.1 you might need to reduce the value of load resistance.Thats why i have kept a potentiometer in my hardware design so that it can be tweaked as needed.

Arduino Tips & Tricks

Understanding Sensing & Interfacing Temperature Sensor with Arduino.

Sensors are very important part of electronic systems. A sensor is a transducer whose purpose is to sense /detect some  some characteristics of its surroundings and provide a suitable corresponding output in the form of  electrical signal.

Example: Blood Sugar Detection Machine

There is a commonly available blood glucose measurement machine which is used by the patients. For measuring the blood sugar first you  prick the skin and put it on the strip that comes with the machine,there is a protein on  the strip which when  comes in contact with the blood sugar produces electrons and hence a voltage is created which is then read by the machine,the machine is pre calibrated to give a corresponding reading. 

Different sensors may have different ways of sensing a same characteristic. In a general  in any sensing device we make use of change in inductance,capacitance or resistance to get the desired output,however the technology used in the sensor affects some important features of a sensor like response time,accuracy,repeatability,lifetime. Power consumption is another important factor that needs to be taken care of while selecting a sensor,because lesser power consumption will give more up time.

ADC

When we talk about the sensors the next thing without which we cannot live are the ADC. These convert the analog voltage into digital voltage. There are many types of ADC available  like Counter type ADC,Parallel comparator type ADC(this is the fastest ),Successive approximation type ADC, Dual slope integrated type ADC. Each one of above have its pros and cons. The atmega328P on the arduino have a 10bit sussesive approximation type ADC. I am not going to go into the details of how it works,you can go here  if you want to read more.

CALIBRATION

This is the next buzz word you will here while dealing with the sensors,right calibration of sensor is very important for accurate measurement,different sensors  may require different ways for calibration,some sensors also come precalibrated.

 As a hobbiest it might not be super critical thing and we can do away with it at times  but on more important areas and in serious implementations like in bio medical instrumentation (like the example above)it is very important to have right calibration. 

HANDS ON 

Interfacing LM35

LM35 has a measurement range of -55*c to 150 *c. It is commonly available sensor that you can find for a price range between 35 to 45 INR. Below is a picture with its pin description.

STEP 1:

Connect the sensor to arduino as below.

STEP 2:

writing the software:

we have to read the analog value at the pin A5 of the arduino and the multiply it with a magic number

int val;
int tempPin = A5;
float reading,temperature
void setup()
{
  Serial.begin(9600);
}
void loop()
{
  val = analogRead(tempPin);
  reading= (val*4.88)
  temperature= reading/10;
  Serial.print("TEMPRATURE = ");
  Serial.print(temperature);
  delay(1000);

}

The magic is in these two lines below but where did these lines come from? Lets understand

  reading= (val*4.88)
  temperature= reading/10;

The ADC on the arduino gets a 5v as reference if you dont change it 

First thing we have done here is we have calculated the step size

Stepsize= Vref/2^n     n=no of bits  here we have a 10bit ADC on arduino.

stepsize= 5/1024 =0.0048828 = 4.88mV

from data sheet of LM35 we know for every 1 degree C rise there is increase of 10mv in the output.

temperature= (analogRead(A0)*4.88mV.)/10mv

If you want to increase the accuracy you can  decrease the Vref. Hope you enjoyed the post and gained something out of it.