eeed lcd displays for raspberry pi quotation

The official Raspberry Pi 7” Touchscreen allows you to add touch inputs to your programs, creating a new way to interact with your projects. It also makes for a fantastic desktop screen for day-to-day use of your Raspberry Pi. Wrap it in one of our screen cases and take it anywhere – events, Raspberry Jams or even just your friends house for a coding evening!

For smaller projects, LCD and ePaper displays are a fun way to add a visual element to your projects. With simple code and wiring, they’re great for projects that require text, menus and navigation.

The Waveshare"s 4inch IPS capacitive touch screen with a hardware resolution of 480x800 capacitive touch screen with 5-point touch tempered glass. This LCD supports Pi 4B/3B+/3A+, another adapter cable is required for CM3+/4 and drives LCD directly through Raspberry Pi"s DSI interface with a refresh rate of up to 60Hz. The backlight can be adjusted by software.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

I"m a bit nervous about posting this but it has worked for me on 3 different Pi models; Pi1B+, Pi2B and Pi3B. Over the last week I had read many column metres of forum posts but nothing worked for my Pi3B so I spent a while doing the following step by step approach and then found it worked on my older Pi models as well. I"m new to Linux so do not claim to know the subtleties but hope this helps.

RS232 serial is all things to all people and was causing me problems over 30 years ago when there was a mix of both 9 and 25 way connectors and we used "dumb" modems as well. The PC (intelligent) transmits its data on a male 9 pin D type on pin 3 (see http://pinouts.ru/SerialPorts/Serial9_pinout.shtml) and receives on pin 2. To communicate with another intelligent device pin 2 at one end must be connected to pin 3 at the other - transmit to receive - and similarly 3 to 2. The cable to do this is known as a crossed or null-modem cable and has 9 way female connectors at both ends.

Note also that there is a system called flow control which might muddy the waters. To make sure that the device at the other end was ready to accept data there are 2 lines in a full interconnection called RTS and CTS. One end asserts RTS (Ready to Send) and the other end responds with CTS (Clear to Send). There is another method called DTR (Data Terminal Ready) and DSR (Data Set Ready) which use wires in the interconnecting cable. Yet another method of flow control is Xon/Xoff. The point of mentioning this is that you should disable all of these at both ends of your comms link - in Realterm for example hardware flow control should be None and neither Transmit nor Receive should be ticked in Software flow control.

Note also if using Realterm on the PC as I do that, when you have selected the port (Com4 - Prolific Serial in my case), the baud rate (115200) and parity None, 8 Data Bits and 1 Stop bit, you must click on Change for the parameters to take effect. Similar instruction apply to puTTY on the PI and are detailed below.

My plan was to use a Pi as a terminal to display the serial output of some PIC based test equipment that I design and use and I set up a PC running Realterm at 115200N81 - other PC terminal programmes may be simpler - and connected it to the Pi3 using a Serial Pi Plus https://www.abelectronics.co.uk/product ... al-Pi-Plus using a crossed (null modem) lead. The Pi Plus board performs the NECESSARY voltage level translation from the 3.3V used by the Pi logic to the + and - 5V (or greater) used by RS232 in the cable. Do NOT connect RS232 wiring direct to the Pi as it may well destroy it. Note that the PC and the Pi both have 9 pin male connectors which is why the crossed lead is required (or an ordinary 9 pin serial lead plus a null modem adaptor and a gender changer if you must). I have since also used eBay interfaces instead of the Serial Pi Plus (search for max3232 DB9) and they are fine but note that TxD0 on the Pi GPIB header goes to TxD0 on the interface board and RxD0 to RxD0. Be careful to get a male version if using a crossed lead and make sure you use the 3.3V supply on the GPIO header and NOT the 5V or the outputs of the MAX3232 could rise to 5V and damage the Pi. If you get a female version you can use a "normal" 9 pin RS232 lead but, as the Pi is an intelligent device the convention is that its serial should be a male.

Use sudo raspi-config option 1 to expand file system and option 9 then Advanced option A7 to enable "login shell" (console) if it isn"t already - reboot.

If "login shell" is enabled on the Pi and the hardware and cabling is correct you will see roughly the same text as appears on the Pi monitor during the boot appearing on the PC Realterm screen. At the end of this you can login to your Pi from Realterm (but you will have to click in the Realterm screen first) using Pi and Raspberry defaults. If all of that works you have proved that you can communicate in both directions over the GPIO serial RS232 connection. If it doesn"t work, stop here and go back and check your interface & cable.

While you are editing /boot/config.txt you will see that enable_uart=0 appears at the end of config.txt; comment it out - #enable_uart=0 and reboot: this I do not understand but I have not been able to get serial comms on the GPIO pins unless it is commented out!

Configure puTTY > Category > Session - for serial 115200 on /dev/serial0 and Category > Serial > Speed = 115200, Data = 8, Stop = 1, Parity = N and Flow Control = none. (I recommend that you highlight “Default Settings” in Category > Session and Save). Note that Jessie uses aliases for the serial as you will see if you list devices - ls /dev

Pi->PC should now work and PC->Pi should also work in puTTY @ 115200 Changing the baud rate is simple. If writing in Python use serial0 and neither ttyS0 nor ttyAMA0. The kernel does the translation and your code is more portable.

There are probably more re-boots in there than required but I was keeping tabs on the devices at each step using ls /dev to find when serial(s) appeared and disappeared.

I hope this is of use to Pi users and saves some time and much frustration. If you find an error or omission please let me know and, if you can throw more light on the subject please do!

I am trying to wire a reed switch based anemometer to the GPIO. I have had no luck so far in being able to read anything from it. I was hoping to find help here.

Exactly! The wire isn"t long at all maybe 4 or 5 feet. It is working if I put a led on the gpio side between the switch and the GPIO pin. The LED will flash as the reed closes.

You need to either set pull down on the GPIO input or add a 10k resistor to 0V. If you do not then your input pin is either connected to 3.3V or floating (which will generate a lot of noise signals).

https://github.com/raspberrypi/weather- ... rection.py reads the wind direction using channel 0 on an MCP342X ADC to convert the resistance value to a digital signal.

The anemometer wind speed conversion in both the poster"s code and the official weather station code doesn"t seem quite right. It assumes that the anemometer cup will accelerate to exactly the incident wind speed and act as a perfect drag device (that is, have a Cd = 1.0). This will not be the case, as the opposite anemometer cup will provide additional resistance and there will also be bearing friction causing the anemometer to turn more slowly than the ‘perfect’ wind speed. I"ve spent many years working with anemometers, and even though hobbyist weather stations running on Raspberry Pis aren"t going to be used for life-critical purposes, we might as well apply the right theory when we make the measurements. A Raspberry Pi has ample processing power to do this; we used to do this in realtime on dataloggers with a 1 MHz Hitachi 6303 8-bit processor (a 6800 clone).

For the official Weather Station, it might be worth the RPF getting a small batch of anemometers type calibrated. City University of London used to have a great and relatively inexpensive calibration service. That way, at least we"d know if the numbers were roughly close, and if the units had any repeatability.

For the official Weather Station, it might be worth the RPF getting a small batch of anemometers type calibrated. City University of London used to have a great and relatively inexpensive calibration service. That way, at least we"d know if the numbers were roughly close, and if the units had any repeatability.

I"ll send a private message to Clive or an email to weather@raspberrypi.org about this. Clive is trying to get the weather station sensors calibrated. The problem we"ve got at the moment isn"t wind speed, wind direction or rainfall, it"s that the three temperature sensors aren"t consistent. The HTU21D, for example, reads 4.4°C warmer than the DS18B20.

scruss wrote:The anemometer wind speed conversion in both the poster"s code and the official weather station code doesn"t seem quite right. It assumes that the anemometer cup will accelerate to exactly the incident wind speed and act as a perfect drag device (that is, have a Cd = 1.0). This will not be the case, as the opposite anemometer cup will provide additional resistance and there will also be bearing friction causing the anemometer to turn more slowly than the ‘perfect’ wind speed. I"ve spent many years working with anemometers, and even though hobbyist weather stations running on Raspberry Pis aren"t going to be used for life-critical purposes, we might as well apply the right theory when we make the measurements. A Raspberry Pi has ample processing power to do this; we used to do this in realtime on dataloggers with a 1 MHz Hitachi 6303 8-bit processor (a 6800 clone).

For the official Weather Station, it might be worth the RPF getting a small batch of anemometers type calibrated. City University of London used to have a great and relatively inexpensive calibration service. That way, at least we"d know if the numbers were roughly close, and if the units had any repeatability.

This was stated in the explanation in the comments section of the python script. It is only a bit of fun for getting a rough guide on wind speed and was never intended to be an exact windspeed meter. I just wrote it as a guide and for teaching my daughter about science etc

If you are reading zero"s means that you don"t have a pullup resistor properly installed. Double check your diagram. An external pullup of pulldown resistor is not required because the rpi pins contain pullup/pulldown circuits. To use them you have to active the circuits in your statement

If you"re feeling really advanced — and to be honest, I don"t think reed-switch anemometers have the resolution for this — throw out measurements where your car is accelerating or decelerating. Cup anemometers can have considerable inertia, so they can read high as the wind dies down and under-read as the wind picks up. This hysteresis is not a huge problem with small plastic anemometers, but with the big old Casella ones were heavy metal.

No, this is not a problem for sure. I am using EXCELLENT pigpio library to detect the reed switch pulses. Moreover I can observe GPIOs pulses using piscope.

[*]If you"re feeling really advanced — and to be honest, I don"t think reed-switch anemometers have the resolution for this — throw out measurements where your car is accelerating or decelerating. Cup anemometers can have considerable inertia, so they can read high as the wind dies down and under-read as the wind picks up. This hysteresis is not a huge problem with small plastic anemometers, but with the big old Casella ones were heavy metal.

I understand your comment about resolution. All solutions I have found on the internet are using resolution 2 pulses per revolution for this kind of anemometer (2 magnets in the anemometer head) . Thanks to the pigpio library I have discovered it is possible to use 4 pulses per revolution (as the reed switch stay closed for some short period, while magnet is passing over). So I am detecting both, rising and falling edge. Now I think my observation is close to the manufacturer numbers (documentation 1 r/s => 1.333 m/s, my calibration 1 r/s => 1.2376 m/s) and the interpolation line in the chart looks reasonable to me.

BTW I am calculating wind speed using 1s sampling pulses generated by hw PWM on Raspberry Pi, instead of measuring time difference between pulses as all other solutions, I have found, do. Do you think it is a good/reasonable approach?

It represents about a 7% difference from the specs. These are not precision devices, and there are all sorts of real-world sources of error, so I would regard this as an entirely acceptable variance. If you want precise wind speed measurements, you have to spend much more money on (e.g.) ultrasonic transducers and much more effort on "siting" the transducer to avoid outside interference with the flow of air over/round it.

This article will walk you through a project where you use a variety of sensors and devices in conjunction with an RPi to gather data about phone calls.

In this telephone log device, a magnet can be secured to the telephone receiver and would close the reed switch when the receiver is in the cradle. Therefore, the position of the handset can be dynamically detected by the change in magnetic force on the reed switch. The goal was to collect information about the content of the phone call while imposing a minimum of work on the user. When many such devices are deployed across many workstations, the data can be published to an IoT server and reviewed by a subscribing dashboard.

We break the project down into small tasks that use different pins on the Raspberry Pi to fulfill specific tasks necessary for the final project. The two rows of GPIO pins on the board all have specific functions which are detailed on a pinout [4]. As you complete one section, leave it assembled when you start on the next and use a different region of your solderless breadboard. That way at the end, the hardware all remains connected, and you just need to alter the code. When considering using this outside of a workshop, you would finalize your design and then have a circuit board made where you could have the components permanently soldered down and made more compact.

The components needed for each section are listed in a bill of materials (BOM) at the start of each section. Some of the parts are generic and could be purchased from a variety of retailers and could be purchased for less. All source code is available under an open source license and provided on GitHub (http://bit.ly/2piVyPz). Alternatively, the source code is also available as Supplementary Material for this article.

The Raspberry Pi Foundation was founded in 2009 with the goal of promoting the academic study of basic computer science. The Raspberry Pi 3 Model B (RPi3) is the most recent hardware iteration, released in February 2016. The hardware of RPi3 includes a system-on-a-chip (SoC) which integrates several key system components onto the same chip to reduce cost and physical size, including a quad-core ARM processor, 1GB of memory (RAM), and a graphics processing unit (GPU).

An RPi is a blank slate without an operating system until one is flashed onto a microSD card which is inserted on the undersurface of the device. As discussed above, there are a variety of operating systems that can be installed on the RPi. Download and follow the official installation instructions for Raspbian with Desktop: https://www.raspberrypi.org/downloads/raspbian/.

After flashing the operating system to a MicroSD card, connect the RPi3 to HDMI, a keyboard and mouse, and Ethernet if available. Connect the micro USB power supply to the connector on the board. You should start to see indicators light on the edge of the board. With time you should see the boot process scroll by on the monitor, and the OS will walk you through the initial setup.

Once your initial setup has been completed and you have reached the Raspbian desktop, load a terminal and update the package manager ‘apt’ (a package manager is a program which downloads a list of available software packages and will install and uninstall them for you with a few commands):$ sudo apt update

This article will primarily use Python to interface and the gpiozero API to interface with attached hardware sensors. Therefore, have ‘apt’ upgrade the existing packages and install new software using the following commands:$ sudo apt upgrade

These packages include the code to allow python to interact with the GPIO interfaces through two different libraries (rpi.GPIO and gpiozero) and some supporting libraries (Table 1).

Now that you have a working current operating system installed, you can start interfacing with devices. The bill of materials for this section is shown above in Table 2. It is recommended that whenever you are attaching new devices to the GPIO pins on the RPi3 that you power down the device before connecting. A solderless breadboard is a useful tool for creating circuits quickly. To use one, you must first understand how the pins are interconnected, shown in Fig. 1.

Solderless breadboards. This diagram shows the typical wiring of the pins of a breadboard. Understanding that the five pin holes on either side of the median in the middle of the board are wired together on each side. However, the left side is not wired to the right side. Components are often arranged in the middle of the breadboard with leads going into holes on either side of the median. The two columns of holes on the far edges of the boards are usually used for power supply and ground, and each column is wired as a whole unit

The pinout of the RPi3 is a useful reference [4]. Some of the pins on the 2 × 20 header are labeled “+3v3 Power” or “+5v power” meaning that these are pins to supply power to devices but, if shorted to ground, could exceed designed power output and overheat. Since all pins in the two rows look the same, board designers and manufacturers usually mark pin 1 with a small circle. In RPi3, a very small rounded corner of the white silkscreen outline on the green board around the header pins denotes pin 1.

Use the electrical schematic and board model in Fig. 2 to connect two LED (light emitting diodes) of any color to the RPi3’s pins (GPIO22 and GPIO27). Resisters are connected in series with the LEDs to limit the amount of current the LED can draw. The maximum current could be calculated with Eq. 1, where the voltage the RPi3 can supply is + 3.3v and the resistor used is 220 Ω, resulting in a maximal current of 15 mA.

LED example. In this example, two LEDs are wired to different GPIO pins and can be controlled independently in both a schematic and b breadboard connections

Ohm’s law is one of the fundamental equations for electrical engineering describing the relationship of voltage and current across an area of resistance. V = voltage, i = current, R = resistance.

This should result in the LEDs lighting in series, 1, then 2, then both, then both off. The gpiozero library documentation describes LED-related functions in more detail [5].

Displays are ubiquitous in many electronic devices today. The display in this project uses a common serial communication protocol called SPI (serial peripheral interface) which uses different pins for a clock signal, data, etc. (Table 3). It uses an open source library by Adafruit to simplify the process of communicating with SPI devices. To begin, mount the display on the breadboard and connect the pins from the breadboard to the RPi3 as seen in Fig. 3.

OLED display example. An LCD allows a program to directly output messages to the user from hardware. Using an OLED display requires some different purpose specific pins such as a clock, data, and chip select pin. a Schematic of wiring an organic LED device onto RPi3 and b the corresponding breadboard connections

Once the display is connected, execute the commands below.$ sudo apt install build-essential python-rpi.gpio python-dev python-imaging python-smbus python-pip git

The last command will load a menu which allows you to configure many of the settings of your RPi. Use the arrow keys and enter/return key to select “Interfacing Options” > “SPI” > “Yes.” Hit Enter to acknowledge “Ok” and returning to the main menu. Hit tab, right arrow, and enter/return to select “Finish.” The RPi is now setup for serial communication and has the Adafruit SSD1306 library which contains instructions for the SSD1306 chip on the display.

Change directories to the folder containing the code for this lesson. Ensure that the file is executable and the python program which will output a message to the display. Open the python file to understand how the python program controls the display.$ python RadIOT_2_OLED.py

This example illustrates the concept of polling a device to determine its state. A simple tactile pushbutton is connected to a pin on the RPi3, and the opposite side of the pushbutton is connected to ground (Table 4). Internally, a pull-up resistor ensures that when the pushbutton circuit is open, the pin on the RPi is tied to + 3.3 V. When the button is depressed, the pin is pulled to ground. The gpiozero library contains many functions for monitoring the state of a pin including the is_pressed method. Use the wiring diagrams in Fig. 4 to connect the push buttons.

Change directories to the folder containing the code for this lesson. Ensure that the file is executable and run the python program which will light the LED when a button is pressed. Open the python file to understand how the python program polls the pushbuttons and then illuminates the appropriate LED.$ python RadIOT_3_Button.py

A reed switch is a simple device with two parallel metal plates that are pulled together by any adjacent magnet (Table 5). These switches are used in a wide variety of consumer-electronics. In this case, the switch will be used to monitor whether a handset for a telephone is in the cradle or not. The magnet attached to the handset will be pulled away from the reed switch, opening the circuit, when the phone is picked up.

Reed switch example. a Schematic of wiring a reed switch to RPi3 and b the corresponding breadboard connections. A reed switch is a simple switch used in security systems, door sensors, and motors. The close proximity of a magnet pushes or pulls thin plates of metal together within the glass envelope. In this example, placing a magnet near the reed switch will close the circuit and the program will cause the LEDs to light

Change directories to the folder containing the code for this lesson. Ensure that the file is executable and run the python program which will poll the state of the reed switch and light the LEDs. Open the python file to understand how the python program polls the reed switch similarly to the pushbutton and then illuminates the appropriate LEDs. A debounce value is used for the reed switch since as the switch closes or opens, there may be a very short period where the connection is intermittently disconnected and connected again. Debouncing is often a good practice on any button or switch.$ python RadIOT_4_ReedSwitch.py

In this example, all of the previously connected devices are used together to create a more complex system (Fig. 6). The code is designed to monitor the reed switch till the handset is picked up opening the reed switch circuit. When the reed switch circuit is closed again, the program outputs a message to the OLED display requesting the user to press one of the two buttons corresponding to the answer which will light up an LED in confirmation that the message was recorded. Also, confirmation is displayed on the OLED display. The code records the response and timestamp to a database file for further analysis later.

Final cumulative example. a Schematic and b the corresponding breadboard connections of wiring LEDs, buttons, a OLED display, and reed switch to RPi3 to create a telephone call logging device for the radiology reading room. If a magnet is glued to the receiver and the reed switch is placed on the phone stand, replacing the receiver on the stand will be detected by the program which will light up the LEDs to get the attention of the user. A question will appear on the screen, and the user can press a button next to an appropriate answer. The LED next to the button will light to give the user feedback that the answer was recorded

To execute the code change to the directory for the exercise, ensure that the file is executable and run the Python program. Then, review the code and comments in your editor of choice.$ python RadIOT_5_Cummulative.py

So far, the device has no capability of storing or communicating the data it has collected. There are several ways of keeping the data selection. First, the data may be stored locally on the RPi3 flash disk, but this approach becomes quickly unmanageable with increasing number of devices. The data may be stored in a network database for processing later, but this process may be too cumbersome for real-time dashboards. Instead, the data may be published through a dedicated network protocol to a lightweight message hub so that databases, real-time dashboards, and other resources may subscribe to the data stream and perform their own respective downstream processing.

Message Queue Telemetry Transport (MQTT) is a lightweight, popular IoT messaging protocol communicating under TCP/IP through the publish-subscribe pattern of communication (Fig. 7). In these communication patterns, IoT devices collect and categorize data by topic but do not specifically address a receiver when sending. Instead, the devices “publish” data to a central resource. Users wishing to consume the data may “subscribe” to specific topics and receive push notifications when data has been published on the topic of choice.$ pip install paho-mqtt

Publisher-subscriber communication. A device may publish on any number of “topics,” denoted by solid and dotted lines. Subscribers may choose to consume any or all topics even without detailed knowledge of the data publishers

The code in RadIOT_6_SendData.py adds basic MQTT capabilities to the RPi3. An example subscriber is included under RadIOT_DBSubscriber.py which may be run on any network-connected computer running Python, not necessarily a Raspberry Pi. The topic and location variables need to be properly configured to ensure the publishers and subscribers are addressing the same topics.

Somehow I missed seeing this question from you back in August.  Sorry about that.  I"m a relative noob at 3d printing and have a Flashforge Creator Pro that seems to work ok.  One thing you have to realize is that this stuff is still pretty clearly in the DIY world and the printers may look pretty but 3d printing has lots of quirks.  I think just the reality that you are moving a print head that is heated to 200-250 C around with a bunch of wires running to it etc. makes it a bit prone to flakiness.  I think most of the printers out there started as open source projects that have been minimally productized.  Most could probably use some serious engineering to make them real consumer items.  Interestingly most of the printers on the market have lots of mods available to improve them once you get them.  By the way - all my comments are regarding the fused filament designs which are the bulk of the affordable ones.  They take plastic filament in one of 2 sizes (1.75mm or 3mm) depending on the printer.  They then feed the filament to a hot end that melts it and deposits it on a print bed to build up the desired device.  The popular and easy materials are PLA and ABS.  Both print below 250C which is relevant due to common choices in the design of the hot end of the print head that limits units to about that temperature (because they incorporate a small amount of high temperature plastic in their feed mechanisms).  It is possible to upgrade (or buy directly) printers to have an all metal hot end which allows higher temperatures.  This adds stuff like Nylon to the materials that are printable (as well as some other plastics).  Personally I like ABS as a decent trade-off between brittleness (PLA is pretty brittle) and strength and ease of printing, although ABS does suffer warping and shrinkage issues.  I"d really like to try out Nylon which looks stronger and overall better but I"ve mostly broken my printer at the moment trying to do the hot end upgrade (like I said - very DIY).

By the way - you do need some software to make use of these things but there are free versions of most.  You need a design program if you are doing designs (there are lots of other folks stuff on places like Thingiverse that can just be downloaded and printed).  There are a variety of free (and of course some very expensive professional) design tools - I use one called 123D Design mostly which is actually from Autodesk and derives from there commercial versions.  You also need a slicer which is the software that takes a design and turns it into commands to the printer to move the head and build up the layers.  There are free ones and generally printers will come with one but I actually bought a program called SImplify3D which is generally acclaimed as the one piece of software in the space that is worth paying for.

I am trying to figure out how would have to go about connecting up multiple LCD displays to the I2C. I was looking at the Adafruit LCD plate which includes 5 buttons and a 16x2 lcd display. First off, can the address on this be changed or is it set at 0x20 only (I only found where can change the address in the programming)? If that can"t be changed, the rest is mute. The other problem would be how to tell the Pi which display to send what data? Would I have to essentially re-write the entire Adafruit CHARLCD setup for the second one changing all the variables or is there a simpler way?

Is there a simpler way to go about using 2 seperate 16x2 LCDs on the same Pi? This is going to be used in order to control some relays in order to turn on/turn off some motors. I have the relays and the motor side of the circuitry working. I can do this fine with one iteration using SPI for the LCD and 5 buttons directly to GPIO pins, however I was wanting to be able to clone it for two of the same devices to be stacked on top of each other and if can get this to work it would be perfect. All the Pi is doing is counting as a reed switch sends a signal up to a set quantity (after a start button is pressed) and then stopping the machine when the count is reached, an error circuit detects a problem or the stop button is pressed. It also has speed up/down buttons for the digital pot and a reset button to restart the program. For a clear picture, I am also using another button to give a Poweroff to the pi since won"t have a direct CLI interface to the Pi. I will also be using two other GPIO pins as the output signals to trigger the relays. I am programming this in Python which I am very new to, even tho I have had experience programming in C++ mostly.

The robot is made with a magnet sensor that can detect when a magnet is nearby. If you have not already, you will need to set up your Raspberry Pi before you can start the project.

The program for this project will tell your "puppet" to do one thing when you bring the magnet close to the magnet sensor, and something else when you move the magnet away. Create the following program in Scratch. Read the tips below the screenshot if you need help.

The old_value and new_value variables keep track of whether GPIO pin 4 was high or low on the last program loop, and whether it is high or low now, respectively.

The magnet sensor in this project is actually a special kind of switch called a reed switch. The reed switch has two very thin pieces of metal inside.

Now, make sure your program and circuit work. Click the green flag to run your program, and then hold the magnet close to the magnet sensor. The LED should light up, and the sound effect you picked should play once. When you move the magnet away, the LED should turn off, and the other sound effect should play once. If everything works properly, then you are ready to connect the circuit to your puppet.

Finally, if the LED lights up and sound effects play, but something still seems wrong (for example, the sound effects play repeatedly, even when you hold the magnet still), there is a problem with your program.

Make sure you securely attach the magnet, magnet sensor, and LEDs to your puppet using tape or glue (tape might be easier to remove if you want to re-use the parts for a different project later).

First, make sure you properly connected the long jumper wires to the breadboard, and to the leads of the LEDs and magnet sensor. The leads might come loose when you move the puppet around, so you should use tape to help secure them. Remember to put the jumper wires into the correct breadboard holes. For example, if the long lead of the LED was originally connected to hole F20, then the jumper wire should also be connected to hole F20.

Make your puppet react to light and darkness. See the Create Light Up Artwork with a Raspberry Pi project for instructions on using the light sensor.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

This website is using a security service to protect itself from online attacks. The action you just performed triggered the security solution. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data.

Application: The actuators/fan run on a signal from an external mechanical switch for a specific period of time. The application has 3 phases as explained in the ALGO below:

Get to know the world"s favorite $25 computer: the Raspberry Pi. You"ll find tips, tricks and more in this unofficial Raspberry Pi tutorial from MakeUseOf. Whether you"re a current Pi owner who wants to learn more, or a potential owner of this credit-card size device, this isn"t a guide you want to miss.

You"ve surely heard of the Raspberry Pi: the palm-sized computer with enough power to run servers or media centers complete with retro gaming; with the connectivity to control security systems and enthusiast projects; and with the software tools to encourage the teaching and understanding of programming.

Since its launch in 2012 the Pi has exceeded expectations, becoming a must-have piece of computer hardware for enthusiasts and tech-heads. For a small project developed to be sold to schools and colleges to teach programming principles, that"s not bad.

It"s also just the tip of the iceberg. Now in its third main iteration, the Raspberry Pi is the must-have compact computer for hobbyists and enthusiasts.

In this guide you"ll find everything you need to know about the Raspberry Pi computer, its background, purpose, system specs, the software it runs and the amazing things it is capable of.

Under development since 2006, the Raspberry Pi is a small computer with the components mounted on a credit card sized motherboard, running Raspbian, a dedicated version of the Linux operating system.

Capable of offering basic office computing, low-level gaming, internet and email access, media playback and many other features regularly expected from a computer in the 21st century, the Pi achieves all of this with a stripped-down component count, an ARM processor and a very low price.

You may be aware that the Pi is not the only small computer project. Over the past few years a number of stripped down, low-cost computers have been released for enthusiasts, in some ways echoing the golden homebrew days of the 1970s and 1980s.

The Arduino: geared towards providing a computer interface to electronics projects. Arduino is more of a control device, however, and can be used in conjunction with the Pi to manage projects with moving components. See What Is Arduino.

Availability for these projects differs from the Pi, which thanks to its low cost (and despite specs lower than ODROID and Gooseberry) has proven extremely popular. This is no doubt in part to the successful management of the supply and delivery chain, as well as the philosophy behind the device.

Designing and building a low-cost computer that is so flexible was the idea of a group of computer programmers such as Eben Upton and David Braben, both of whom are members of the Raspberry Pi Foundation. Their ethos for the creation of this computer was to develop hardware that children and students could use to learn about programming. The low cost of the computers means that they can be sold to schools around the world, thereby offering educational opportunities for all.

Enthusiasts around the world use the Pi for far more than its original purpose. Media center software exists as a version of Kodi, and there are several Linux distributions that can be installed.

Retro gaming is possible (modern titles since around 2000 require far greater hardware resources) as is multimedia playback; remarkably the Pi is capable of HD video. You might also use the device as a web server, print server, stop motion camera, time-lapse camera, digital photo display server, NAS controller, home security computer… the possibilities are endless!

Later in this guide we"ll be taking a look at operating systems and media center software. Meanwhile, Section 8: Fascinating Uses for the Pi provides an overview of many other uses for the computer.

You would be right to expect the specs of the Raspberry Pi to be low, but the device isn"t so stripped back that it"s useless. Rather, it combines quad-core processing and a sizable cache with intelligent engineering to deliver a pleasing computing experience.

Some aspects of the Pi are left to you to deal with. It typically ships without a case, storage, or cables, although bundles can be bought with these included. If you opt for the board alone, you"ll be surprised to find how much is available in terms of peripherals and storage. This is largely due to the hardware options that the device supports.

There are four versions of the Raspberry Pi: Model A, Model B, Compute Module, and Zero. We"ll be ignoring the Compute Module in this guide; this ships direct to equipment manufacturers, typically for smart home projects.

Raspberry Pi Model B: which comes in two current flavors:Raspberry Pi 2: this is $35 with a BCM2837 SoC, 900 MHz 64-bit quad-core CPU, 1 GB RAM shared with the GPU and four USB ports.

Raspberry Pi 3: for $35, this is also equipped with a BCM2837 SoC, this time with a 1.2 GHz 64-bit quad core CPU, and 1 GB of shared RAM. Again, there are four USB ports.

Raspberry Pi Zero:Available for just $5 (a $10 wireless version is also available) this 32-bit slimline Raspberry Pi features the BCM2835 SoC, with 1 GHz CPU and 512 MB RAM, shared with the GPU.

Several aspects of the Pi"s hardware (the Pi Zero notwithstanding) has remained standard. It has a micro-USB power connector, with a HDMI port. An Ethernet port is connected to the USB bus, and a microSD port. Then there"s the dual-purpose 3.5 mm mini jack, for audio and video if your output device doesn"t have HDMI.

In addition, each model is a slightly different size. The latest Model A and Model B (the Pi 2 and Pi 3) boards are 85.60 mm × 56.5 mm (3.370 in × 2.224 in), whereas the Pi Zero is 65 mm × 30 mm (2.56 in × 1.18 in). The depth of the board varies too; the Zero is just 5 mm deep, whereas the Model B boards are 17 mm deep due to the additional hardware connectors.

One of the greatest things about the Pi is that the developers have never rested on their laurels. Revisions are regularly rolled out, both hardware and software. For instance, the Model A and Model B were originally launched with 256 MB of RAM. This was upgraded in 2014 to 512 MB. However, the Raspberry Pi 2 and 3 ship with 1 GB of RAM.

An array of GPIO pins is provided with the Raspberry Pi. These can be used for a wide variety of tasks, from controlling the Pi (perhaps a game controller, or other input device) to controlling or accepting power from a secondary device.

Although detailed use of the GPIO pins is beyond the scope of this guide, safety isn"t. You will need to adopt the same careful approach to connecting to these pins as you would on any computer or circuit board. Without proper care, you risk blowing up your Raspberry Pi"s CPU if the GPIO pins are used incorrectly. Make sure you test the voltage through the cable before connecting to your Pi!

A prototype of the computer that would become the Raspberry Pi dates back to 2006. The Raspberry Pi Foundation was formed in 2008, but it wasn"t until 2011 that the possibility of the computer being released as a viable project became apparent.

While the original 10,000 boards were built in Taiwan and China, the Pi is now built in the United Kingdom, in South Wales. Following its launch on February 29th 2012, 500,000 boards had been sold by September 2012. According to the Raspberry Pi Foundation, by November 2016 an amazing 11 million Raspberry Pis have been sold!

As we"ve seen, the Pi ships as-is. When you open the box, all you will find is a small motherboard with the required components attached. It"s up to you to finish the job with cables, a case and storage media.

Cases for this device come in all shapes and sizes, from Lego to downloadable cardboard cutouts. In addition to a case, you"ll need certain cables to enjoy your Raspberry Pi, as well as storage, typically an SD card. Let"s explore your options.

The first thing you will notice about a brand new Pi is that it ships without a case. This is a little similar to running a PC motherboard without bothering with the tower – unwise! The solution, of course, is to find or build a case -- what"s available?

The Punnet case is a popular option, being as it is completely free and easy to construct. It exists as a printable design that can be cut out and constructed in thin plastic, thick paper, or card, providing a home for your Pi computer.

There is little that you can"t build with Lego, and a case for the Pi is not an exception. As with any DIY case for this computer, you will need to make sure that there is sufficient space for the cables and memory card, and that the case offers sufficient ventilation. You can use the Punnet case design to help with the positioning of these gaps.

Various cases are available for the Pi. The only complication comes when choosing the right case for your device. The best places to find a case are eBay, Amazon, as well as:

It"s also possible to build your own case from various materials. This eLinux page lists many variations. Later revisions of the various Pi models are equipped with a couple of mounting holes, which you can use to mount the Pi. You can find their position via this template from Pi Spy.

Handheld game consoles like the Nintendo Gameboy, old routers, keyboards and even video game cartridges (specifically those for the Nintendo 64) can all be used as housings for the Raspberry Pi. A certain amount of planning will be required, and you will need to have the right equipment to hand to make the conversion possible. Old toys and music players can also be repurposed to hold a Pi.

Whichever case solution you use, make sure that it is sturdy, will protect the Raspberry Pi from knocks, and offer the necessary airflow for keeping the processor cool.

Ethernet: if you don"t plan on using Wi-Fi (perhaps your Pi doesn"t have built-in wireless, and you don"t yet have a USB Wi-Fi dongle), you will need this to connect to your router.

HDMI cable: remarkably, the Pi has a single HDMI port, for high definition video and audio. Even more remarkable is the Mini-HDMI on the Raspberry Pi Zero. A standard HDMI adaptor is included, but if you have a Mini-HDMI cable, this will fit perfectly.

Audio cable: the Pi includes a special dual-purpose 3.5 mm mini jack. Its first purpose is for audio, ideal for connecting your pocket-sized computer to speakers. This is useful if you"re not using HDMI, or want to send your audio to a different device.

Micro-USB cable: while you should use a power adaptor in most cases (see below) a cable capable of carrying 5V will prove useful if you need to power the Pi from your PC. You can also employ a portable smartphone charger as your power source.

One of the most important elements of any computer is the storage, from which the operating system is run and data stored. The Pi doesn"t have a hard disk drive -- instead, it is equipped with a microSD card slot.

You should aim to purchase a high rated SDHC card for use with this mini-computer. Capacity should be 8 GB or more – more storage offers the best results. The Pi uses the storage much like a solid-state drive, which is why the SDHC format is used for its improved read/write resilience.

Additional storage can be attached via the USB ports. It"s also possible to forego the microSD card and boot from a USB device, but you"ll still require the microSD card to set this up.

One option is to purchase a PiDrive, a hard disk produced by Western Digital. This ships with a custom version of NOOBS (see below), enabling you to install multiple Pi operating systems onto a 375 GB or 1 TB HDD. The advantage to this is that you don"t have to install a new OS each time you need to start a new project.

USB keyboard and mouse: pretty vital if you plan on entering any text or using the configuration menus. After the device has been connected and configure, you can use the USB ports for other purposes (such as additional storage or wireless networking), instead of entering text commands via SSH.

Whatever you"re planning to do with your Raspberry Pi, make sure you give it the respect it deserves. It may be small, but it is just as prone to damage from static electricity and knocks and blows – not to mention extremes of temperature – as any other computer.

Once your Raspberry Pi is suitably protected in its box or case, you can then continue to use it much as you would any other device. However, starting up and shutting down can prove problematic (particularly the latter) – see section 5.1: Start and Shut Down Safely for more details.

With the correct cables and storage prepared you"ll be able to install an operating system on your Pi. Due to the hardware profile, however, this isn"t a device that will run Windows or Mac OS X. Instead, you will need to rely on a Linux distribution.

There are several distros available for the Pi, but the most popular is Raspbian, a cleverly named Debian port configured specifically for the Pi. Installing this can be tricky if you don"t follow the instructions, and like any OS installation on the Raspberry Pi it requires additional software to make your SD card bootable.

Other distros can be downloaded and installed on the Pi, but the most interesting of these is Android. Let"s not get ahead of ourselves, though: keep reading to find out how to install Raspbian.

The following steps are for setting up the software on Windows. Linux users can write to the SD card with the dd tool, while Mac OS X users can also use dd or RPi-sd card builder utility. Full instructions for these platforms are available online.

To get started installing Raspbian, visit Raspberry Pi Downloads and download the latest version. You will also need Win32 Disk Imager. With both downloaded, unzip Win32 Disk Imager and insert your card into the card reader.

With Raspbian installed on the microSD card, you"re all ready to go. Safely remove it from your PC, insert it into the Pi and power up the computer, with your HDMI cable and keyboard connected.

When you boot the Pi for the first time, you"ll be taken to the Raspbian Wheezy PIXEL desktop environment. From here, open the Menu, go to Preferences, and open Raspberry Pi Configuration.

Whichever configuration tool you choose, you should check for updates before proceeding. Use the Update option in your configuration menu to do this, and follow the instructions. Once this is done, you should also expand the root partition.

You can enable this in the desktop configuration tool, or raspi-config in the command line. As long as your Pi is connected to the same network as your computer and you have an SSH utility such as PuTTY (available from www.chiark.greenend.org.uk/~sgtatham/putty/download.html) running, you should be able to connect via SSH in seconds.

Configuring PuTTY is straightforward: in the Session screen, add the IP address of the Raspberry Pi in the Host Name (or IP address) field. Ensure SSH is selected and click Open. You can login to your Pi using the credentials provided by your chosen distro (for instance if you use Raspbian, the username and password are displayed on the Raspbian download page).

Don"t have a monitor for your Raspberry Pi? The answer is to connect via SSH -- but how can you do this without having a monitor connected to enable SSH?

Fortunately, there is a workaround. Before inserting the microSD card into your Pi, open the Boot directory in your desktop operating system"s file manager. Here, create a text file called SSH, being careful not to give the file an extension.

For example, if the file was called ssh.txt, rename the file so that it is simply named ssh. After closing the file manager and safely removing the microSD card, insert it into, and restart, the Pi. With this SSH file present, you"ve activated the provision for secure connections over your network, and can connect to the Pi with the default username and password.

Moving data to and from your Raspberry Pi can be a bit tricky without SSH enabled. Fortunately, you can get around this using FTP software. Several are available, but you need one that supports SFTP (I use FileZilla). This is essentially SSH over FTP, and offers a secure route for sharing data with your Pi.

For instance, if you wanted to copy software to your Raspberry Pi from your PC, you could easily do this via SFTP. Or you might want to copy photos created with the Raspberry Pi camera module back to your PC.

All you need to do to use SFTP is input the IP address of your Raspberry Pi, login with the username and password, and then drag the files in question between the two panes of your FTP application.

If you want to go a step further and fully configure your Raspberry Pi before booting, you need the PiBakery. This is a very useful utility that has a copy of Raspbian Jessie built into it. Put simply, you configure the operating system, then write it to the microSD card.

For instance, you might configure a wireless network connection, or enable SSH. You can instruct it to install software on its first boot, or run a VNC server. Once the preferences are set, you bake them into Raspbian, writing a specific disk image to the microSD card.

Raspbian is the most popular choice for Raspberry Pi owners, but is by no means the only distro available for the computer.Arch: this is an ARM variant of the main Arch Linux, and boots in around 10 seconds. Versatile, but with a steep learning curve for Linux beginners.

RISC OS: available free of charge to Pi users (RISC usually requires a license) this is the modern version of the British operating system, which like the Pi was developed in Cambridge.

Android: several versions of Android have been released for the Raspberry Pi, using the code from the AOSP (Android Open Source Project) repository. To date, there hasn"t been a version that successfully matches the flexibility of the hardware with the software, but you may have some fun trying it out.

Also available is NOOBS (New Out of the Box Software), a tool that can be copied directly to a freshly formatted microSD card, and used to install your preferred operating system. You"ll find NOOBS available for download at www.raspberrypi.org/downloads. There are two versions, a lite download that will pull the operating system you want onto the microSD card, and a full download for offline installation.

There are two ways to use the Pi. The first is to rely on the text-driven user interface, which is ideal for particular tasks. Alternatively, there is the second option, using the mouse-driven GUI, which will be far more familiar to most users.

As you should be aware if you"ve read the guide to this point, the Pi"s Raspbian operating system is based on the Debian distribution of Linux. However, the desktop, PIXEL, is based on the LXDE environment.

You might have noticed that the Raspberry Pi does not have an on or off switch. So how can you power it down? The easy option is to click the Shutdown option from the main menu on the desktop.

Thanks to the SD card that is used as a storage device in the Pi, switching the computer off by disconnecting the power cable or unplugging at the mains will more than likely corrupt the OS, preventing you from being able to reboot. In this situation, a reinstallation will be required.

This has various switches and conditions. For instance, the above instruction will shut the Pi down in one minute. But adding -h now to the end of the line will force an immediate shutdown.

Although running the Raspberry Pi with the GUI desktop rather than the text-based command line is probably preferable in many situations, as with any Linux distro there will be times when you need to use the command line option to issue instructions.

To get the most out of a Pi running a Linux distro such as Debian, you will need to become more familiar with the principles of the operating system. Our Newbie"s Getting Started Guide to Linux is a great place to start as well as this list of useful commands every Raspberry Pi user should know.

There are two main methods for installing software onto your Pi. The first is the traditional Linux route of downloading and installing from a remote server, known as a repository. This is done from the command line: apt-get update

One of the key reasons for the development of the Pi was to create an affordable computer that children and students could use as a platform for application development. Programming on the Pi is made simple by the provision of various tools, available bundled in with the Raspbian operating system.

Whether you"re happy learning to program applications with Python or you prefer one of the alternatives that can be installed, you"ll need a plan or outline for your application, plenty of time to spend getting it right and some basic background in coding.

The primary programming language provided with the Pi is Python. If you have experience with this language then you should be able to start coding straightaway.

Of course, if you"re 7, the chances are that you haven"t had the time to get to grips with Python, what with collecting worms and buying sweets. Fortunately, the Raspberry Pi ships with a useful Python module called Pygame, essentially a game construction kit that should enable you to have fun and learn basic game building principles at the same time. There are also several programs included that have been written in Python, so you can get an idea of what can be achieved.

Note that Python is a cross-platform scripting language, which means that you can program on a Windows computer or a Mac, save the project and then run it on your Pi.

Although Python is considered the core programming tool for young users of the Pi, other languages can also be used:Java is one option, and is pre-installed on current versions of the Raspberry Pi"s Raspbian Jessie operating system

Scratch 2.0 is included in the Raspbian distro, an easy to use development tool aimed at children with a drag-and-drop GUI that makes building conditions and in-game situations extremely simple. Scratch is developed by MIT Media Lab and Lifelong Kindergarten Group, and Flash support is provided by the Pepper Flash plugin for Chromium.

Arduino IDE is also available for the Raspberry Pi, allowing you to connect an Arduino and create a sketch (a program in Arduino, written in C++). Connecting these two devices together presents many options for home automation.

Python is a widely used programming language, and you can find plenty of tips for use across the web. Check out our article on 5 best websites to learn Python, as well as our list of top Raspberry Pi programming resources.

The tutorial is quite comprehensive, so you will need to put plenty of time aside for going through it. Reference guides are also provided explaining the various libraries and the functions in each, enabling you to get a grasp of what can be done with this language.

As you learned earlier, the Pi was conceived as a computer that pupils and older students could use for programming in schools. But how successful has this aim been?

Unfortunately there are no explicit figures, although there are accounts of schools making bulk purchases and people buying the devices to donate to education facilities. It is estimated that around 20% are in the hands of children, and there are likely to be many more young people who have a Pi in the family.

Initially, it seemed that some schools may be ill-prepared to deal with teaching on the Pi. Fortunately there is a useful Creative Commons licensed manual produced for UK educators, CAS Raspberry Pi Educational Manual, which can be downloaded via the Raspberry Pi website and through the integrated app store. There"s also a teacher"s guide to the Raspberry Pi available on the official website.

Thanks to the USB ports and networking, a Pi makes an excellent media device, both as a small set-top box streaming media from a larger PC or the web and as an all-in-one unit, accessing external hard disk drives and other storage media and outputting the media to your TV or sound system.

In order to do this, however, you will need to install a special version of Kodi, configured to run on the Raspberry Pi. Several full disk images are available:OSMC

In addition, retro gaming distros Recalbox and RetroPie can also run Kodi, and come with it either preinstalled (Recalbox) or as an option to install (RetroPie). If you choose to install the full disk image, it"s a good idea to have a spare SD card, one for your Raspberry Pi"s usual operating system and a second for Kodi. This way you can swap between roles as easily as switching the cards over, making the little computer even more flexible.

Although setting up Kodi on the Pi is relatively easy, and getting started for viewing videos and enjoying music is simple, using the Pi as a media center is a little different to the usual setup.

Unless you"re using an extremely large capacity microSD card (SDHC with a maximum of 32 GB is the recommended format, although some types of SDXC are believed to work) you will need to run media from an external hard disk drive, a USB storage device or an external optical drive. Kodi offers various streaming options thanks to its wide selection of add-ons, of course… it all really depends on your preferred media choices. You should also consider a powered USB hub if you"re planning on maxing out your existing expansion options.

A network attached storage (NAS) box might be one solution for media stored on HDD, for instance, or you might rely on sharing content across your home network from a PC in your office, bedroom or den. Funnily enough, you could use a Pi to manage a home-built NAS.

Installing Kodi is only the first step in setting up your Pi media center. A variety of add-ons enable you to extend this software considerably, many of which we"ve covered at MakeUseOf.

While running a Raspberry Pi as a media centre seems to be an extremely popular option, it isn"t the only way in which this versatile little computer can be put to work.

There are dozens of ways in which the Pi can be used to achieve various purposes and to complete many different tasks, from using it as a NAS to running a web server or even a carputer.

Over the years we"ve shared with you many ways in which you can use the Raspberry Pi. We"ve collected the most fascinating and achievable in this section of the guide for you to consider, and to appreciate the magnificence of this tiny home computer.

The connection is via a USB to microUSB cable, and requires that you jailbreak the Kindle, install a terminal emulator and a tool called UsbNetwork. Once the Kindle has been unlocked and the necessary utilities installed, you will be on the way to using the e-reader as a display for your Pi. Note that this can only be done with the Kindle models that are equipped with an integrated keyboard. Full steps for building a KindleBerry Pi -- which requires a Kindle 3 -- can be found at www.ponnuki.net/2012/09/kindleberry-pi/.

We"ve already seen how the Pi can be configured as a media centre. One great way to serve media files to your Raspbmc device is with a NAS box – another easy to setup project (assuming you have a second Raspberry Pi).

Although not suitable for streaming HD videos (due to the use of the Samba server software), a Pi NAS box can be set up as a low-power NAS (see, what NAS is).

You will also need to configure the Samba server on your Pi (running one of the Debian distros) and the Samba client on your Windows, Linux, Mac or Android device.

End your TV nostalgia d