Ashish Adhikari

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  1. The very first program you write when you start learning a new programming language is: "Hello World!". The program itself does nothing more than printing a “Hello World” text on the screen. So, how do we get our Arduino to display the "Hello World!"? In this video, I will be showing you how to get started with the small 0.91 (128x32) and 0.96 (128x64) I2C OLED displays. There are 100s of tutorials on the web explaining the same thing in different ways, but I couldn't find one that tells me all about the OLED display and how to use it in different scenarios. It took me some time to work it all out. So, I thought I should create a tutorial on what I have learned and combine all the features and ways the OLED displays can be used in our projects. Step 1: Things We Are Going to Learn Today In this video we will be talking about: - What is an OLED display? - Then we will have a closer look at the 0.91 (128x32) and 0.96 (128x64) I2C OLED displays - Next we will talk about installing the Adafruit Library to your Arduino IDE - Then we will connect NodeMCU and Arduino to an OLED display - Next we will have a look at the code and display some graphics and text on it - We will also talk about applying Custom Fonts and displaying Images - Then we will connect Multiple OLEDs to a micro-controller using I2C Multiplexer - Finally, we will talk about few common errors people make while using the OLED displays Step 2: Hardware Requirement For this tutorial we need: - A Breadboard - A 0.91" (128x32) and 0.96" (128x64) I2C OLED displays - Arduino UNO/NANO (whatever is handy) - NodeMCU - TCA9548A I2C multiplexer - Few Connecting Cables - and a USB cable to upload the code Step 3: What Is an OLED Display? OLED or organic light-emitting diode is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound (millions of small LED lights) that emits light in response to an electric current. OLEDs are used to create digital displays in devices such as television screens, computer monitors, portable systems such as mobile phones, hand-held game consoles and PDAs. An OLED display works without a backlight because it emits visible light. There are many types of OLED displays available in the market based on their - Sizes - Color - Brands - Protocol - SPI (Serial Peripheral Interface) or I2C - Passive-matrix (PMOLED) or active-matrix (AMOLED) control scheme In this tutorial, I am going to talk about connecting the blue color 0.91 (128x32 OLED) and 0.96 (128x64 OLED) I2C OLDE displays to an Arduino NANO and NodeMCU. I2C bus technology uses only 2 pins of the MCU so we have heaps available for other sensors. Step 4: Closer Look Lets have a closer at these two displays. At the back of these displays there are heaps of SMD capacitors and resistors soldered on-board; but, since its an I2C device we only care about these 2 pins (SCL and SDA) The display connects to Arduino using only four wires – two for power (VCC and GND) and two for data (serial clock SCL and serial data SDA), making the wiring very simple. The data connection is I2C (I²C, IIC or Inter-Integrated Circuit) and this interface is also called TWI (Two Wire Interface). - The on-board pins can be in different order, so always triple check before hooking it up to your project. - Operation voltage is between 3v to 5v but, it is best to use the guidance from the manufacturer's datasheet. - Sometimes we need to use 2 displays in our projects. So, how can we achieve this? The trick is to have a configurable address on your display. This unit has a configurable address between 0x78 and 0x7A. Just by unsoldering the 0Ohm resistor from one side and hoking it up to the other side or just by putting a global solder we can change the address. We will talk about it in depth when we hook up multiple displays to an Arduino in the later section of this tutorial. In picture these displays look very big. But, practically speaking they are tiny. They are made of 128 x 32/64 individual OLED pixels and do not require any back-light. Just have a look at this and see how small it is. Even though they are small they can be very useful in any electronic projects. Step 5: Library There are several libraries available to control these displays. In past I have used the "u8glib library" but I find the AdaFruit library very easy to understand and use in our projects. So, I am going to use the AdaFruit library in this tutorial. To control the OLED display you’ll need the "adafruit_GFX.h" library and the "adafruit_SSD1306.h" library. There are two ways you can download and install the library to your Arduino IDE. Method 1 Go to the "Library manager" and search "adafruit_SSD1306" and "adafruit_gfx" Select the latest version and hit the Install button. Once installed you can use these libraries in your program. Method 2 These two libraries can be also be downloaded from github (you need both): I will provide the links in the description below. The display library: The GFX library: Once downloaded, copy the Adafruit_SSD1306-master folder from the downloaded zipped file into the Arduino libraries folder. This folder is usually found at Documents > Arduino > libraries on Windows systems. On Linux it is usually found at home folder > Arduino > libraries. Finally in the Arduino library folder, rename the Adafruit_SSD1306-master folder to Adafruit_SSD1306. Even if you don’t rename that’s fine. Now, lets have a look at the "Adafruit_SSD1306.h" file Two things we need to know in this library: 1. If you want to use the smaller display use the default 128_32 otherwise for the bigger display comment the 128_32 and uncomment the 128_64 2. If you have soldered the 0x7A Address on the board (which we will talk about later) then use the 7 bit 0x3D address for the bigger displays, otherwise use the default 0x3C address. For the smaller displays the address is 0x3C. Step 6: Wiring 128 X 64/32 OLEDs Lets start by connecting the NodeMCU to the display. The first and most important thing to note is that some of the displays may have the GND and VCC power pins swapped around. Check your display to make sure that it is the same as the image. If the pins are swapped, make sure to change the connections to the Arduino or NodeMCU. - NodeMCU OLED Wiring OLED VCC – NodeMCU 3.3V OLED GND – NodeMCU GND OLED SCL – NodeMCU D1 OLED SDA – NodeMCU D2 - Arduino Uno OLED Wiring OLED VCC – Arduino 5V OLED GND – Arduino GND OLED SCL – Arduino Uno A5 OLED SDA – Arduino Uno A4 - Arduino MEGA 2560 OLED Wiring OLED VCC – Arduino 5V OLED GND – Arduino GND OLED SCL – Arduino MEGA 2560 pin 21 OLED SDA – Arduino MEGA 2560 pin 20 Step 7: Code Adafruit library comes with really good examples for both 128x32 and 128x64 displays. The Library is located under File > Examples > Adafruit SSD1306 > and then the display type in the Arduino IDE. We are going to use the 128x32 I2C example and will modify it to work with both 128x64 and 128x32 displays fist by hooking it up to an Arduino and then to a NodeMCU board. The code starts by including both the Adafruit libraries. In this tutorial I am going to stress on only those parts of the code which are necessary for us to load on both boards and displays. If you want to know more about the code please drop a comment on my blog or in the comments section below and I endeavour to get back to you. - First we are going to load the code to an Arduino Nano connected to a 128x32 display. We can use the code as is without any modifications. 128x32 uses 0x3C address so this bit looks all good here, lets double check the header library, yes its also using the 0x3C address and the display type is 128x32. - Now lets connect the 128x64 display. As we know it uses the 0x3C address by default so we don't need to update the address in either the code or the library. We just need we need to comment the 128_32 and uncomment the 128_64 in the header library and change the LCDHEIGHT to 64 in our code. - Now to run the same code on a NodeMCU we need to change one more line in our code. The "#define OLED_RESET 4" > "#define OLED_RESET LED_BUILTIN" rest of the code is same as Arduino Pretty much to display anything we first need to clear the previous screen using display.clearDisplay(); // Clear the buffer Then draw the object testdrawline(); // Draw a line Show it on the hardware display.display(); // Make them visible on the display hardware! Wait for some time before displaying the next item. delay(2000); // Wait for 2 seconds In this example we are displaying few items like text, lines, circles, scrolling text, triangles and more. Go ahead and use your imagination and display whatever you want on these tiny displays. Attachments Download Download Step 8: Customizing Text & Adding Images Sometimes your code needs to display custom fonts and images. If you are very good in bit mapping then you just need to create a byte arrays by turning on or off the tiny LEDs of the display to create custom fonts and images. However, I am not very good in doing these mappings and don't want to spend hours creating the bit map tables. So, what are my options? I generally use two websites to generate custom fonts and images. The links are provided in the description below. Custom Fonts ------------ Go to the font converter website, select the font family, style, size, Library Version as "Adafruit GFX Font" and then hit the "Create" button. On the right hand side of this page you can see how your font is going to look like on the actual display. Based on your selection the webpage generates the fonts header file. Create a file called "modified_font.h" in the same folder where your code is and copy and save the generated code into it. Then you just need to include the header file in your code to use the custom font. #include "modified_font.h" Then, you just need to set the font before displaying the text to apply the custom font to it. display.setFont(&Your_Fonts_Name); You can get the name of the font from the header file you just added to your project. Thats it, easy. Memory is always a concern while using custom fonts, so always consider the bytes that will be consumed by the memory. Just remember Arduino UNO has only 32K of memory. Custom Images ------------- To display a bitmap image on your screen you first need to create a 128 x 64/32 sized image. I am using the good old "MS Paint" to create a 128 x 64 bitmap image which I will then upload to this image converter website. The website converts images into byte-strings, which can be used with Arduino and OLED displays. Start by uploading the image to the website. Then put a check on the "Invert image colors" check-box and change the "Output code format" to "Arduino Code" next select the orientation and hit the "Generate Code" button to generate the byte array. The "Preview" section shows you how your image will look like on the actual display. I have included the code along with this tutorial which you can use to display your images. You just need to replace the array in my code with the one you just generated and then load it to your Arduino. Attachments Download Download Step 9: Connecting 2 Displays Connecting two 128 x 64 displays to your project is easy. You just need to unsolder the 0Ohm resistor from 0x78 address and put it on 0x7A and then use the 0x3D address in your code instead of the default 0x3C. You must be wondering why we are using the 0x3C and 0x3D address and not the actual 0x78 and 0x7A. Arduino accepts 7-bit address and not the 8-bit hardware addresses. So, we first need to convert the 8-bit address to binary, and then chop off the least significant bit to get the 7 bits. Then convert the 7 bits to HEX to get the 0x3C or 0x3D addresses which you enter in your code. First, initialize the display by giving it a unique name: Adafruit_SSD1306 display1(OLED_REST); Adafruit_SSD1306 display2(OLED_REST); Then in your code use the display 1 and display 2 to call the begin statements with the device addresses in them: display1.begin(SSD1306_SWITCHCAPVCC, 0x3C); // display 1 op address 0x3C display2.begin(SSD1306_SWITCHCAPVCC, 0x3D); // display 2 op address 0x3D That's it, you can now go ahead and do whatever you want using either Display 1 or Display 2 in the rest of your code. I have provided an example with this tutorial. Wiring is exactly the same as what we have done before, pretty much you just need to add another display to the same I2C pins of either the Arduino or NodeMCU. Based on the addresses, the MCU then sends the data on the I2C data line. Attachments Download Step 10: Connecting More Than 2 Displays 3 More Images Now, what if you want to hook up more than 2 displays? Arduino has limited number of pins and hence you cannot have more than a certain amount of shields attached to it. Moreover, it has only one pair of I2C buses. So, how can we attach more than 2 I2C displays to an Arduino? The trick is to use a TCA9548 Multiplexer. TCA9548 allows a single micro-controller to communicate with up to '64 sensors' all with the same or different I2C address by assigning a unique channel to each sensor slave sub-bus. When we talk about sending data over 2 wires to multiple devices we then need a way to address them. Its same as the postman coming on a single road and dropping the mail packets to different houses because they have different addresses written on them. The Multiplexer connects to 3V3, GND, SDA and SCL lines of the micro-controller. The slave sensors are connected to one of eight SCL/SDA slave ports on the board. The channels are selected by sending the TCA9548A its I2C address (0x70 {default} - 0x77) followed by the channel number (0b00000001 - 0b10000000). You could have at the max 8 of these multiplexers connected together on 0x70-0x77 addresses in order to control 64 of the same I2C addressed parts. By connecting the three address bits A0, A1 and A2 to VIN you can get different combination of the addresses. I will explain this in-depth in my next tutorial on TCA9548A breakout board. For now, lets just hook up 8 OLEDs to this board and have a quick look at the code. Connection: VIN to 5V (or 3.3V) GND to ground SCL to I2C clock SDA to I2C data Then wire up the sensors to VIN, GND and use one of the SCn / SDn multiplexed buses Now, Int the code lets start by including the "Wire" library and by defining the multiplexers address. #include "Wire.h" #include #define MUX_Address 0x70 // TCA9548A Encoders address Then we need to select the port we want to communicate to and send the data on it using this function: void tcaselect(uint8_t i) { if (i > 7) return; Wire.beginTransmission(MUX_Address); Wire.write(1 << i); Wire.endTransmission(); } Next we will initialize the display in the setup section by calling "u8g.begin();" for each display attached to the MUX "tcaselect(i);" Once initialized, we can then do whatever we want just by calling the function "tcaselect(i);" where "i" is the value of the multiplexed bus and then sending the data and clock accordingly. Attachments Download Download Step 11: Advantages and Disadvantages The image of an OLED is beautiful. However, OLEDs also have disadvantages. Because OLED screens contain organic material, their lifespan is shorter than LCD displays. Additionally, many OLED displays get burn-ins after showing the same image for a long time. After a burn-in, the image stays on the screen even after showing another image. So make sure you keep refreshing the screen every few seconds. Water can instantly damage the organic materials of these displays. Advantages No need for a backlight Displays are very thin and lightweight Low power consumption Viewing angles are wider than LCDs Brightness and contrast are great High speed and have low response time Deep black color Disadvantages Costly technology Short lifecycle OLEDS are more likely to burn-in Water damage Step 12: Common Errors To conclude the tutorial lets talk about few common errors people make while using these displays: - Always triple check the pins before using it in your project - Pick up the right library address in the header file and in your code #define SSD1306_I2C_ADDRESS 0x3C // in Adafruit_SSD1306.h and display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // in your code If the address is wrong the OLED will not display anything - The display size must be changed in the driver before it can be used. If it is not changed you will get an error message when attempting to verify the code #error ("Height incorrect, please fix Adafruit_SSD1306.h!"); - If using NodeMCU make sure you replace the OLED_RESET from 4 to LED_BUILTIN #define OLED_RESET LED_BUILTIN I have scene people making all sorts of things using this OLED display. Some have even made video games and all. I am really not interested in making a video game using this tiny display. However, I will now leave you to explore your imaginations and come out with amazing ideas. - Blog: - Add Image: - Custom Text: - Adafruit display library: - Adafruit GFX library: - u8glib library: or If you want to use the smaller display use the default 128_32 otherwise for the bigger display comment the 128_32 and uncomment the 128X64 NO_ACK in your code (just uncomment the type of screen you are using) (fonts are in the fonts library) Attachments Download Download Download Download
  2. Has this ever happened to you? You come back from a romantic dinner date and when you open the shutter door of your garage you realize that you left the garage light ON. You spent few hours outside with your partner to impress her and all the time this light bulb was on. You immediately turn around and look at her face to see a silent anger on her face. Alright, enough of that. So, in this tutorial, I am going to turn on and off the garage light using a PIR sensor. When the sensor detects a moving object, it turns on the light bulb and when the moving object is gone, it turns it off. Lastly, I am going to make sure that light bulb only turn on during the night time (when its dark). Step 1: Logic In this project, I will be using a PIR sensor along with an LDR to turn on or off a light bulb using a Relay. The things I need to consider before designing the circuit are: - The bulb should only turn on when the room is dark and when a motion is detected. - The bulb should turn off after 30 seconds of the object leaving the sensors proximity. - Most important, we need to place the LDR in a place where it doesn't turn off the bulb as soon as it lights up. Step 2: Hardware For this tutorial we need: A General Purpose PCB 2 x HC-SR501 PIR Sensor 2 x 1N4148 Small Signal Fast Switching Diodes 1 x 1N4007 High Voltage, High Current Rated Diode to protect the micro-controller from voltage spikes 1 x LDR 1 x 10K Trimmer Potentiometer 2 x 470 Ohms Resistor 1 x 10K Resistor 1 x 1K Resistor 1 x 2N3906 General Purpose PNP Transistor 1 x 2N2222 General Purpose NPN Transistor 1 x 5V Relay 1 x LED to display the status 5 x Terminal Blocks 1 x 220V to 5V Buck Step Down Module Few Connecting Cables And General Soldering Equipments Step 3: Assembly Lets first connect the LDR and setup the light detection bit. As we all know we need to setup a voltage divider to use the LDR in a circuit, so, I am adding this 10K POT and 470ohms resistor to setup the voltage divider bit. By adjusting the resistance of the POT we can adjust the intensity of sunlight at which this circuit will operate. Now, lets install the PIR sensor. Connect the VCC to +5v and GND to ground. Then connect the 1N4148 diode to the OUT of the sensor. In this circuit, I am installing just one sensor however in the actual project I have used 2 sensors to capture a bit more than 180 degrees. So, to avoid the sensors from back-feeding each other we need to install a diode to the OUT pin of each sensor. If you want to capture motion at 360 degrees you may need 3 to 4 sensor and diode pair to achieve that. Now that we have the PIR sensor and the LDR in place we need to add the 'AND' functionality. To achieve this I am adding a general purpose PNP transistor. When a motion is detected 'and' when the sunlight is at a certain intensity (adjusted by the POT) current flows out of the transistor. Next, we need to amplify the current received from the collector of the PNP transistor and turn on and off the LED indicator and the Relay. A general purpose NPN transistor is used to achieve this. That's it all done. Step 4: What Have I Have Made So, this is what I have made. On my board components are pretty much soldered everywhere, but you may like to have them nicely installed to give it a bit more cleaner look. OK, so lets check out how this works. Step 5: Demo Alright, I have placed the board on this table to do a quick test. I haven't hooked up a light bulb to the circuit yet. However, the LED indicator should serve the purpose of this demonstration. So, now I am going to turn off the light and make the room dark. Let's see if the sensor picks up motion and lights up the LED. Tada, it works. Now, lets turn on the light of the room and see if the LED indicator turns off or not. Yessss, that works. OK, finally just want to make sure that the light bulb turns off after 30 seconds of me moving out of the sensors proximity. Boom, and that concludes the project. I can now install it on the ceiling and make my partner happy. Instead of having 2 to 3 PIR sensors you can use one and install it at the corner of the wall. However, that will require a fair bit of wiring either inside the roof or on the ceiling, which will be way more expensive and tedious than installing 3 sensors an d putting the device in the middle of the room. You can also swap the Arduino with a NodeMCU board and do a remote data logging to log the time when the sensor detected motion or when the light went on to record when people entered your garage and how long they stayed in there. Step 6: Areas of Applications of PIR Sensors This setup can be used to: * Automate All Outdoor Lights * Automate Lights of Basement, Garden or Covered Parking Areas * Automate Lift Lobby or Common Staircases Lights * Automate bedside or night lamp * Create a Smart Home Automation & Security System and more.. Step 7: Thanks Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video.
  3. Just before creating my next projects tutorial, which will be using a PIR sensor, I thought I might create a separate tutorial explaining the working of a PIR sensor. By doing that I will be able to keep my other tutorial short and to the point. So, without wasting time let’s discuss what is a PIR sensor and how we can use it in our project. Step 1: Basic What is a PIR sensor? PIR or "Passive Infra-Red" sensor is a "Pyroelectric IR Sensor" which generates energy when exposed to heat. Everything emits some low level of radiation, the hotter the object is, the more radiation is emitted. When a human or an animal (with IR radiation wavelength of 9.4µMeter) approaches the sensors range the sensor detects the heat in the form of infrared radiation. The sensor only detects the energy emitted by other objects and don't produce any, that's why the sensor is called a PIR or "Passive Infra-Red" sensor. These sensors are small, cheap, rugged, low-power and very easy to use. Step 2: Hardware For this tutorial we need: 1 x Breadboard 1 x Arduino Nano/UNO (Whatever is handy) 1 x PIR Sensor 1 x LED and a 220 ohm current limiting resistor to test the connectivity Few connecting cables A USB cable to upload the code to the Arduino & General Soldering Equipments Step 3: Architecture As we can see the sensor has two sides: 1. Top or the Sensor Side 2. Bottom or the Components Side The Top consist of a specially designed 'High-Density Polythene' cover called "Fresnel Lens". This lens focuses the infrared rays to the underlying 'Pyroelectric Sensor'. 9.4 µMeter infrared rays can easily pass through the polyethylene cover. The sensors sensitivity range between 6 to 7 meters (20 feet) and the detection angle is 110 degrees x 70 degrees. The actual sensor is inside a sealed metal can. The can basically protects the sensor from noise, temperature and humidity. There is a tiny window made of IR-transmissive material to allow the IR signals to reach the sensor. Behind this window are 'two' balanced PIR sensors. In idle state, both sensors detect the same amount of IR radiation. When a warm body passes by, it first intercepts one of the two sensors, causing a positive differential change between the two halves. And then, when it leaves the sensing area, the reverse happens, and the sensor generates a negative differential change. When the pulse changes or in other words the PIR sensor detects motion, the output pin changes to "digital high" or 3.3V. The bottom bit consists of a bunch of circuitry. Few of them are of our interest. - Most PIR sensors have 3-pins VCC, GND and OUT. VCC and GND are to power the module (Operating voltage: DC 5V to 20V). The OUTPUT pin is the one which communicates with the micro-controller by sending digital pulse high (3.3v) when a motion is detected and digital low (0v) when no motion is detected. The pin-outs may vary between modules so always triple-check the pin-outs. - The BISS0001 or the "Micro Power PIR Motion Detector IC" gets the output from the sensor and after doing some minor processing it produces the digital output. - The module has two potentiometers one to adjust the sensitivity (which is up to 7m) and the other to adjust the time for which the output signal should stay high when an object is detected (it ranges from 0.3s to 5 mins). - There are 3 more pins on this module with a jumper between them to select the trigger modes. > 1st one is called "non-repeatable trigger" - this one goes low as soon as the delay time is over. > 2nd one is called "repeatable trigger" - it stays high as long as the object is in the proximity and will turn off once the object is gone and the delay is over. I will be using this mode for this project. If you want to do a quick test before going ahead with this tutorial please follow the steps below. A testing is also a good idea to test the range and duration of sensing. Step 4: Connecting Without Arduino - Connect the VCC to the +5v rail of the breadboard - Connect the GND to the -ve rail - Connect the LED along with a 220 ohm resistor to the OUT pin of the sensor Now, when the sensor detects a motion, the output pin will go "high" and the LED will light up. Move back and forward to find out the sensing the range. Then to test the duration walk in front of the sensor and then walk away and use a stopwatch to find out how long the LED stayed on. You can adjust the time or sensitivity by adjusting the POTs on the board. Step 5: Connecting With Arduino Now, to do the same with Arduino connect the VCC of the PIR sensor to the 5v pin of Arduino. Then connect the OUTput pin to D13 and GND to the Ground pin of the Arduino. Now, connect the LED along with a 220 ohm resistor to the D2 pin of the Arduino. Thats it, now you just need to upload the code and test if everything works the way it should. You can replace the LED with a Buzzer (to raise an alarm when an object is detected) or a Relay to drive a high voltage circuit. To learn more about relays please have a look at my tutorial Number 4 - "Driving a Relay with an Arduino". Step 6: Code The code is very simple * Start by defining the pin number 2 and 13 as LED pin and PIR pin respectively * Then we need to define the pin modes. LED pin to be the OUTPUT pin and PIR pin to be the INPUT pin * Next we need to read the value of the PIR pin and see if it is HIGH * If the value is HIGH, then turn ON the LED otherwise turn it OFF Step 7: Areas of Application of PIR Sensors PIR sensors can be used to: * Automate Opening and Closing of Doors * Automate All Outdoor Lights * Automate Lights of Basement, Garden or Covered Parking Areas * Automate Lift Lobby or Common Staircases Lights * Detect Presence of Human and Raise an Alarm * Create a Smart Home Automation & Security System, and many more.... Step 8: Demo So, this is my setup for the testing of the PIR sensor. The sensor is hooked up to the breadboard and is sitting on the table. As I am in front of the sensor the LED is on. Now, lets do a quick test. Currently, the sensor is in its idle state. I am going to walk in front of the it to activate the sensor. Tada, the LED just turned on after detecting my presence. The light stays on as long as I am in the sensors proximity. OK, lets walk away and start my stop watch to see if it turns off after 5 seconds. Success, everything worked the way I wanted. Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video.
  4. DRIVING A RELAY WITH AN ARDUINO Hello everyone, welcome back to my channel. This is my 4th tutorial on how to drive a RELAY (not a relay module) with an Arduino. There are hundreds of tutorial available on how to use a "relay module" but I could not find a good one that shows how to use a Relay and not a Relay module. So, here we are to discuss how a relay works and how we can hook it up to an Arduino. Note: If you do any work with "mains power" such as 120v or 240v AC power wiring, you should always use proper equipments and safety gears and determine whether you have adequate skill and experience or consult a Licensed Electrician. This projects is not intended for use by children. Step 1: Basics A Relay is a large mechanical switch, which is toggled on or off by energizing a coil. Depending on the operating principle and structural features relays are of different types, such as: 1. Electromagnetic Relays 2. Solid State Relays 3. Thermal Relays 4. Power Varied Relays 5. Reed Relays 6. Hybrid Relays 7. Multi-dimensional Relays and so on, with varied ratings, sizes and applications. However, in this tutorial we will only be discussing about an electromagnetic relays. Guide to Different Types of Relays: 1. 2. Step 2: My Relay (SRD-05VDC-SL-C) The relay I am looking at is a SRD-05VDC-SL-C. It is very popular relay among Arduino and DIY electronics hobbyists. This relay has 5 pins. 2 for the coil. Middle one is COM (common) and the rest of the two are called NO (Normally Open) and NC (Normally Close). When current flows through the coil of the relay, a magnetic field is created that causes a ferrous armature to move, either making or breaking an electrical connection. When the electromagnet is energized the NO is the one which is on and NC is the one which is off. When the coil is de-energized the electromagnetic force disappears and the armature moves back to the original position turning on the NC contact. The closing and releasing of the contacts results in powering on and off of the circuits. Now, if we look at the top of the relay the first thing we see is SONGLE, it is the name of the manufacturer. Then we see the "Current and Voltage Rating": it is the maximum current and/or voltage that can be passed through the switch. It starts from 10A@250VAC and goes down till 10A@28VDC Finally the bottom bit says: SRD-05VDC-SL-C SRD: is the model of relay. 05VDC: Also known as "Nominal Coil Voltage" or "Relay Activation Voltage", it is the voltage necessary for the coil to activate the relay. S: Stands for "Sealed Type" structure L: is the "Coil Sensitivity" which is 0.36W C: tells us about the contact form I have attached the datasheet of the relay for more information. Step 3: Getting Hands on a Relay Let’s start by determining the relay coil pins. You can do it either by connecting a multimeter to resistance measuring mode with a scale of 1000 ohm (since the coil resistance normally ranges between 50 ohm and 1000 ohm) or by using a battery. This relay has 'no' polarity marked on it since the internal suppressing diode is not present in it. Hence, the positive output of DC power supply can be connected to any one of the coil pins while negative output of DC power supply will be connected to the other pin of the coil or vice versa. If we connect our battery to the right pins you can actually hear the *clicking* sound when the switch turns on. If you ever get confused in figuring out which one is NO and which one is NC pin, follow the steps below to easily determine that: - Set the multimeter to resistance measuring mode. - Turn the relay upside-down to see pins located at its bottom part. - Now connect one on the multimeter's probe to the pin in between the coils (Common Pin) - Then connect the other probe one by one to the remaining 2 pins. Only one of the pins will complete the circuit and will show activity on the multimeter. Step 4: Arduino and a Relay * The question is "Why to use a relay with an Arduino?" A micro controller's GPIO (general purpose input/output) pins cannot handle higher power devices. A LED is easy enough, but large power items such as light bulbs, motors, pumps or fans required more sneaky circuitry. You can use a 5V relay to switch the 120-240V current and use the Arduino to control the relay. * A relay basically allows a relatively low voltage to easily control higher power circuits. A relay accomplishes this by using the 5V outputted from an Arduino pin to energize the electromagnet which in turn closes an internal, physical switch to turn on or off a higher power circuit. The switching contacts of a relay are completely isolated from the coil, and hence from the Arduino. The only link is by the magnetic field. This process is called "Electrical Isolation". * Now a question arises, Why do we need the extra bit of circuit to drive the relay? The coil of the relay needs a large current (around 150mA) to drive the relay, which an Arduino cannot provide. Therefore we need a device to amplify the current. In this project the NPN transistor 2N2222 drives the relay when the NPN junction gets saturated. Step 5: Hardware Requirement For this tutorial we need: 1 x Breadboard 1 x Arduino Nano/UNO (Whatever is handy) 1 x Relay 1 x 1K resistor 1 x 1N4007 High Voltage, High Current Rated Diode to protect the micro-controller from voltage spikes 1 x 2N2222 General purpose NPN transistor 1 x LED and a 220 ohm current limiting resistor to test the connectivity Few connecting cables A USB cable to upload the code to the Arduino and general soldering equipments Step 6: Assembly * Lets start by connecting the VIN and GND pins of the Arduino to the +ve and -ve rails of the breadboard. * Then connect one of the coils pin to the +ve 5v rail of breadboard. * Next we need to connect a diode across the electromagnetic coil. The diode across the electromagnet conducts in the reverse direction when the transistor is turned off to protect against a voltage spike or the backward flow of current. * Then connect the Collector of the NPN transistor to the 2nd pin of the coil. * The Emitter connects to the -ve rail of the breadboard. * Final, using a 1k resistor connect the Base of the transistor to the D2 pin of the Arduino. * Thats it our circuit is complete, now we can upload the code to the Arduino to turn on or off the relay. Basically, when +5v flow through the 1K resistor to the Base of transistor, a current of about .0005 amps (500 microamps) flows and turns on the transistor. A current of about .07 amps starts flowing through the junction turning on the electromagnet. The electromagnet then pulls the switching contact and moves it to connect the COM terminal to the NO terminal. * Once the NO terminal is connected a Lamp or any other load can be turned on. In this example I am just turning on and off a LED. Step 7: The Code The code is very simple. Just start by defining the digital pin number 2 of the Arduino as the Relay pin. Then define the pinMode as OUTPUT in the setup section of the code. Finally, in the loop section we are going to turn on and off the relay after every 500 CPU cycles by setting the Relay pin to HIGH and LOW respectively. Step 8: Conclusion * Remember: It is very important to place a diode across the coil of the relay because a spike of voltage (inductive kickback from the coil) is generated (Electromagnetic Interference) when the current is removed from the coil due to the collapse of the magnetic field. This voltage spike can damage the sensitive electronic components controlling the circuit. * Most Important: Same as capacitors, we always under-rate the relay to mitigate the risk of relay failures. Lets say, you need to work at 10A@120VAC, don’t use a relay rated for 10A@120VAC, instead use a bigger one such as 30A@120VAC. Remember, power = current * voltage so a 30A@220V relay can handle up to a 6,000W device. * If you just replace the LED with any other electrical device like fan, bulb, fridge etc., you should be able to turn that appliance into a smart device with an Arduino controlled power outlet. * Relay can also be used to turn on or off two circuits. One when the electromagnet is on and the second one when the electromagnet is off. * A Relay helps in Electrical Isolation. The switching contacts of a relay are completely isolated from the coil, and hence from the Arduino. The only link is by the magnetic field. Note: Short circuits on Arduino pins, or attempting to run high current devices from it, can damage or destroy the output transistors in the pin, or damage the entire AtMega chip. Often this will result in a "dead" pin of the micro-controller but the remaining chip will still function adequately. For this reason it is a good idea to connect OUTPUT pins to other devices with 470Ω or 1k resistors, unless maximum current draw from the pins is required for a particular application Step 9: Thanks Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video.
  5. Introduction ---------------- Hi Friends, I am back again with another Arduino based home automation project. This time I am trying to make my partner's life easy by installing a collision avoidance system in the garage to help her park the car safely without hitting the garage wall. So, in this video, I am going to use an ultrasonic sensor to calculate the car's distance from the garage wall and display it using green, yellow and red LEDs. The color of LEDs indicates whether to keep moving, slow down, stop or go back. The total cost of the project is around $20 - $25. Step 1: Logic The project has 3 phases Phase 1: Waiting for the car In this phase the device keeps looking for a moving object within the sensors proximity. If an object enters the proximity then one of the three LEDs turns on based on how far the moving object is. If the object is way too close, then a noise is made to make the moving object aware of the distance. Phase 2: No car in the garage If there is no object in the proximity then turn off all the LEDs. Phase 3: The car has stopped moving (Parked in the right spot) If the object has stopped moving and is still in the proximity wait for 20 CPU cycles and then turn off the LEDs. Step 2: Hardware Requirement For this very simple project we need: - A Perfboard - An Arduino nano/uno (whatever is handy) - A Red, Green and a Yellow LED (Light Emitting Diode) - 3 x 220ohm resistor for the LEDs - One HC-SRO4 Ultrasonic Sensor - A Buzzer shield or A buzzer and a 100 ohm resistor - A 220v AC to 5v DC Buck step-down module - One Female Pin Header Strip - An Ethernet cable - Some connecting cables - A USB cable to upload the code to the Arduino - and general soldering equipments Step 3: Assembly Let start by connecting the LEDs to the board. Connect the Red LED to pin D2, Yellow LED to D3 and the Green LED to D4 of the Arduino by putting in a 220ohm resistor between the Arduino board and the LEDs. Now lets connect the Buzzer to analogue pin A0. Next, connect the Trig pin of the Ultrasonic Sensor to D5 and the Echo pin to D6 of the Arduino. Once all the modules are connected to the Arduino board, its time for us to connect all the positive and negative pins together. Connect all the positive pins of the modules to the +5v supplied by the Buck Step-Down Module and the negative pins to the -ve terminal of the Module. That's it, we can now upload our sketch to the board. In this assembly I am using 3 LEDs to display the distance, however you can replace the 3 LEDs with a RGB LED, or you can also use an array of LEDs like an audio level indicator to display the movement of the car. Step 4: My Setup OK now lets see what I have made. I have installed the Arduino, buzzer, the ultrasonic sensor and the three 220 ohms resistors on one Perfboard. The 3 LEDs and the power module is installed on a second Perfboard. I will be covering the LEDs with a translucent cover to give it a nice look. The 220v power supply will be connected to the screw terminal block. The base unit will then be connected to the LEDs and the power supply with an Ethernet cable. Step 5: The Code int trigPin = PD5; // Sensor Trip pin connected to Arduino pin D5 int echoPin = PD6; // Sensor Echo pin connected to Arduino pin D6 int redLED = PD2; // Red LED connected to pin D2 int yellowLED = PD3; // Yellow LED connected to pin D3 int greenLED = PD4; // Green LED connected to pin D4 int buzzer = A0; // Buzzer connected to Analogue pin A0 long TempDistance = 0; // A variable to store the temporary distance int counter = 0; // Counter value to check if the object has stopped moving void setup() { Serial.begin(9600); pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); pinMode(redLED, OUTPUT); pinMode(greenLED, OUTPUT); pinMode(yellowLED, OUTPUT); pinMode(buzzer, OUTPUT); } void loop() { long duration, Distance; digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW); duration = pulseIn(echoPin, HIGH); Distance = (duration/2) / 74; // Distance in Inches if(counter < 20){ // Do the rest if the car is still moving if (Distance > 200) { // Nothing in the garrage turnThemAllOff(); } if ((Distance > 55) && (Distance <= 200)) { // Turn on Green LED digitalWrite(greenLED, HIGH); digitalWrite(yellowLED, LOW); digitalWrite(redLED, LOW); noTone(buzzer); } if ((Distance > 15) && (Distance <= 55)) { // Turn on Yellow LED digitalWrite(yellowLED, HIGH); digitalWrite(redLED, LOW); digitalWrite(greenLED,LOW); noTone(buzzer); } if (Distance <= 15) { // Turn on Red LED digitalWrite(redLED, HIGH); digitalWrite(greenLED,LOW); digitalWrite(yellowLED, LOW); noTone(buzzer); } if (Distance < 8) { // Item is way to close - start the buzzer tone(buzzer, 500); } } if ((Distance == TempDistance) || ((Distance+1) == TempDistance) || ((Distance-1) == TempDistance)){ if(counter >= 20){ // Turn off the lights if the object hasn't moved for 20 cycles (no change in distance) Serial.println("No movement detected, turning off the lights"); turnThemAllOff(); } else { counter++; } } else { counter = 0; // Reset counter if there is a movement } TempDistance = Distance; Serial.print(Distance); Serial.println(" inches"); Serial.print("Counter : "); Serial.println(counter); delay(500); } // Function to turn the LEDs off void turnThemAllOff(){ digitalWrite(redLED, LOW); digitalWrite(greenLED,LOW); digitalWrite(yellowLED, LOW); noTone(buzzer); } Start the code by defining the constants and the global variables that will be used throughout the code. Then define the pin modes in the setup section of the code. Then create a function to turn off all the LEDs and the buzzer. Now, calculate the "Distance" in inches by reading the values received from the Ultrasonic Sensor. Then by checking the value of the "Distance" we will turn on and off the LEDs based on how far the object is. If the distance is greater than 200 then turn off all the LEDs and the buzzer as the object is out of range. Else if it is between 55 and 200 then turn on the green LED. If the object is between 15 and 55 then turn on the yellow LED, and if the object goes closer than 15 inches then turn on the red LED until it reaches 8 inches. When the distance becomes less than 8 start the buzzer along with the red LED. Next bit of the code is to set the value of the counter based on the cars movement which then decides when to turn off the LEDs. It compares the value of "Distance" with the "TempDistance" and if the values are same (object hasn't moved) then increments the counter. If the object moves any-time during this process the counter is reset to 0. Finally the "TempDistance" is set to the value of "Distance". Just before comparing the Distances we also need to check if the counter value has exceed 20. I am doing this to stop the below code from executing if the car is in a steady position. Lastly we just need to add a small delay to our sketch to pause the code for a while. Step 6: Quick Demo So this is how I have installed the unit in my garage. As I walk close to the sensor the light changes from green to yellow to red and ultimately the buzzer goes on when I am too close to the sensor. In my case I have installed the buzzer next to the Arduino however I will recommend you to install the buzzer along with the LEDs. If you want you can also flash the red LED when the buzzer goes on. So now, my partner can park the car easily without making any assumptions. Doesn't matter how many times she fail her driving test she is not going to break my wall (even when she is drunk). Not that I am asking her to drive when she is drunk (just kidding). Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video.
  6. Introduction --------------- Hi Everyone, This is my 1st Arduino's tutorial video. In this video i am going to show you how to use a LDR or Light Dependent resistor to turn on and off another circuit or a LED. Wouldn’t it be really cool if whenever a room gets dark, a light bulb automatically turns ON and eliminates the darkness? In this very simple project, I am focusing on eliminating darkness. You can even use this as an emergency lighting system. Step 1: Principle The LDR is a special type of resistor which allows a lower voltage to pass through it (high resistance) whenever its dark and higher voltages to pass (low resistance) whenever there is a high intensity of light. We are going to use a 10k resistor along with the LDR to create a voltage divider circuit. The varying resistance of the LDR is converted to a varying voltage that the analog pin of the Arduino will then be using in its logic. Step 2: Harware Reqirement For this very simple DIY Arduino project we need: - a breadboard - an arduino uno/nano (whatever is handy) - LED (Light Emitting Diode) - LDR (Photoresistor) - A 10K Resistor for creating the voltage divider and a 220ohm resistor for the LED - Few breadboard friendly connecting wires - and a USB cable to upload the code to the Arduino Step 3: Assembly - Connect the 3.3v output of the Arduino to the positive rail of the breadboard - Connect the ground to the negative rail of the breadboard - Place the LDR on the breadboard - Attach the 10K resistor to one of the legs of the LDR - Connect the A0 pin of the Arduino to the same column where the LDR and resistor is connected (Since the LDR gives out an analog voltage, it is connected to the analog input pin on the Arduino. The Arduino, with its built-in ADC (Analog to Digital Converter), then converts the analog voltage from 0-5V into a digital value in the range of 0-1023). - Now connect the other end of the 10K resistor to the negative rail - And the the second (free) leg of the LDR to the positive rail Pretty much this is what we need for the light sensing. Basic circuits like this can be done without an Arduino aswell. However, if you want to log the values and use it to create charts, run other logics etc. I will recomend an Arduino or ESP8266 or may be a ESP32 for this. Now, as we want our circuit to do something in the real world other than just displaying the values on the computer screen we will be attaching a LED to the circuit. The LED will turn on when its dark and will go off when its bright. To achieve this we will: - Place the LED on the breadboard - Connect the 220ohm resistor to the long leg (+ve) of the LED - Then we will connect the other leg of the resistor to pin number 13 (digital pin) of the Arduino - and the shorter leg of the LED to the negative rail of the breadboard Step 4: The Code const int ledPin = 13; const int ldrPin = A0; void setup() { Serial.begin(9600); pinMode(ledPin, OUTPUT); pinMode(ldrPin, INPUT); } void loop() { int ldrStatus = analogRead(ldrPin); if (ldrStatus <= 200) { digitalWrite(ledPin, HIGH); Serial.print("Its DARK, Turn on the LED : "); Serial.println(ldrStatus); } else { digitalWrite(ledPin, LOW); Serial.print("Its BRIGHT, Turn off the LED : "); Serial.println(ldrStatus); } } Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next Instructable.
  7. Hi Everyone, In this tutorial I am going to show you how to charge a Lithium 18650 Cell using TP4056 chip utilizing the solar energy or simply the SUN. Wouldn’t it be really cool if you can charge your mobile phones battery using the sun instead of a USB charger. You can also use this project as a DIY portable power bank. The total cost of this project excluding the battery is just under $5. The battery will addup another $4 to $5 bucks. So the total cost of the project is some what around $10. All components are available on my website for sale for really good price, the link is in the description below. Step 1: Hardware Requirement For this project we need: - A 5v Solar Cell (make sure it is 5v and not anything less than that) - A general purpose circuit board - A 1N4007 High Voltage, High Current Rated Diode (for reverse voltage protection). This diode is rated at forward current of 1A with peak reverse voltage rating of 1000V. - Copper Wire - 2x PCB Screw Terminal Blocks - A 18650 Battery Holder - A 3.7V 18650 Battery - A TP4056 battery protection board (with or without the protection IC) - A 5 V power booster - Some connecting cables - and general soldering equipments Step 2: How the TP4056 Work Looking at this board we can see that it has the TP4056 chip along with few other components of our interest. There are two LEDs on board one red and one blue. The red one comes on when it is charging and the blue one comes on when the charging is done. Then there is this mini USB connector to charge the battery from an external USB charger. There are also these two points where you can solder your own charging unit. These points are marked as IN- and IN+ We will be utilizing these two point to power this board. The battery will be connected to these two point marked as BAT+ and BAT- (pretty mush self explanatory) The board requires an input voltage of 4.5 to 5.5v to charge the battery There are two versions of this board available in the market. One with battery discharge protection module and one without it. Both boards offer 1A charging current and then cut off when finished. Furthermore, the one with protection switches the load off when the battery voltage drops below 2.4V to protect the cell from running at too low (such as on a cloudy day) - and also protects against over-voltage and reverse polarity connection (it will usually destroy itself instead of the battery) however please check you have it connected correctly the first time. Step 3: Copper Legs These boards gets really hot so I will be soldering them a bit above the circuit board. To achieve this I am going to use a hard copper wire to make legs of the circuit board. I will then be sliding the unit on the legs and will solder them all together. I will put 4 copper wires to make 4 legs of this circuit board. You can also use - Male Breakable Pin Headers instead of the copper wire to achieve this. Step 4: Assembly The assembly is very simple. The solar cell is connected to the TP4056 battery charging board's IN+ and IN- respectively. A diode is inserted at the positive end for the reverse voltage protection. Then the BAT+ and BAT- of the board is connected to the +ve and -ve ends of the battery. (That all we need for charging the battery). Now to power an Arduino board we need to boost up the output to 5v. So, we are adding a 5v voltage booster to this circuit. Connect the -ve end of the battery to the IN- of the booster and +ve to IN+ by adding a switch in between. OK, now lets have a look at what I have made. - I have connected the booster board straight to the charger however I will recommend putting a SPDT switch there. So when the device is charging the battery its only charging and not getting used Solar cells are connected to the input of the lithium battery charger (TP4056), whose output is connected to the 18560 lithium battery. A 5V step-up voltage booster is also connected to the battery and is used to convert from 3.7V dc to 5V dc. Charging voltage is typically around 4.2V. Voltage booster's input ranges from 0.9 to 5.0V. So it will see around 3.7V at it's input when the battery is discharging, and 4.2V when it's recharging. The output of the booster to the rest of the circuit will keep it's 5V value. Step 5: Testing This project will be very helpful to power a remote data logger. As we know, the power supply is always a problem for a remote logger and most of the times there is no power outlet available. A situation like that forces you to use some batteries to power your circuit. But eventually, the battery will die. Question is do you want to go there and charge the battery? Our inexpensive solar charger project will be an excellent solution for a situation like this to power an Arduino board. This project can also solve the efficiency issue of Arduino when in sleep. Sleep saves battery, however, the sensors and power regulators (7805) will still consume battery in idle mode draining the battery. By charging the battery as we use it, we can solve our problem. Thanks again for watching this video! I hope it helps you. If you want to support me, you can subscribe to my channel and watch my other videos. Thanks, ca again in my next video. TP4056.pdf