Category Archives: Newsworthy

Home Protection with Raspberry Pi

Planning to go on a vacation, but afraid of who will look after your home for you? Worry not, for the mighty Raspberry Pi (RBPi) is here. Not only will RBPi look after your entire house, it will send you an email of what is happening in your home and let you see it on your mobile or on a PC. How cool is that?

Most alarm systems incorporate three primary sensors. The first is a temperature sensor to detect the rise in temperature in case of a fire. The second is an intrusion detection sensor to detect if an intruder has gained access to the insides of the house and third is a motion detection sensor. Apart from these primary sensors, you may add smoke detectors and cameras according to your necessity.

The software consists mainly of a database to store all the events with a time stamp, a dashboard to display the status of the sensors, configure them and to program the alarm system. The Raspberry Pi also acts as a web-server to send email alerts and to display the dashboard on a remote computer or Smartphone.

Depending on the size of the home, its vulnerability and the number of sensors being used, you could divide the area into a number of zones. This makes it easier to arm the sensors belonging to a specific zone. For example, a door and few windows of your home may be facing a busy street during the day and you may decide not to arm the sensors in this zone in the daytime. As night falls, the street gets deserted and you may want the sensors in that zone to be armed for the night.

Dividing the home into zones also has the advantage of knowing in which area or areas the alarm has been triggered. The camera for that zone can then be switched on to assess the situation visually.

Since RBPi runs on Linux, and Linux multitasks very well, the software runs in the background. The software is programmed to wake up RBPi about once every minute and check in on each of the armed sensors in all the zones. If there is no activity, it simply updates the logs for the database and the dashboard and goes back to sleep.

If a sensor trips, or generates an activity, Raspberry Pi records it in its logs, and sends you an email with the details. The dashboard then indicates the alarm condition in the zone where the alarm originated. You have a choice of turning off the alarm after checking it out.

You can login to the server from a remote PC using a username and a password. The web-browser will display the dashboard and a green button lets you know that the RBPi is running your home alarm software and is transmitting the information from the sensors. If the alarm system goes down for some reason, or there is a problem with the connectivity between the Raspberry Pi and your computer, this green button will turn red within a minute. You can now proceed to test, arm or disarm the sensors in each zone. For details of software and setup, refer here.

What Is Back EMF And What Does It Do?

Newton’s third law talks about conservation of energy. In the electromagnetic world, this is best manifest in the form of Lenz’s law, which states – “An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux.”

To understand it in simple terms, the wire in the diagram experiences a downward force because the magnetic field of the permanent magnet reacts with the magnetic field created by the current flowing in the wire. If you were to reverse the direction of flow of current in the wire, the wire would move up instead. This is also called the motor effect, since this is the way motors work.

The wire (formed into a square loop), experiences a torque because the current flowing in the two arms of the loop are not in the same direction, causing the forces on the wire to be in opposite directions. The torque turns the wire loop. By having many such wire loops in its rotor, the motor is able to turn heavy loads.

Since there are two opposing magnetic fields operating when the motor turns, the speed of the motor is governed by the balance between the two. However, the two magnetic fields are never equal, as there is the mechanical friction of the bearings to be overcome to keep the motor rotating, and the difference between the two is called the Back EMF.

Although Back EMF is a good and necessary phenomenon that makes running of motors possible, it assumes menacing proportions in the operation of relays and solenoids. A relay or a solenoid consists of a coil or a large number of turns of wire on an iron core. One of the properties of such an arrangement is the coil stores energy when current passes through it. This, by itself, is nothing to worry about, unless the current is suddenly stopped. This is where you may want to read Lenz’s law again.

When the switch is opened, the current from the battery stops flowing instantly. However, the energy in the relay or solenoid “opposes the original change in magnetic flux”, which is now trying to collapse. The coil can do this only by keeping the current flowing across the gap in the switch. The only way it can do this is by creating a Back EMF high enough to generate an arc across the gap. The arc is sustained until the energy in the inductor dissipates.

Now, arcs in any form are dangerous, and the best way of handling them is to quench them as quickly as possible. In normal operation, a semiconductor switch such as a transistor replaces the resistor and switch shown, and is turned on or off to operate the relay. An arc can blow or damage a transistor in the fraction of a second.

The solution is rather simple. A flyback diode (also called a free-wheeling diode / snubber diode / suppressor diode / catch diode) is connected across the solenoid. When the switch is closed, the diode remains reverse biased and inactive. When the switch opens, the diode conducts to let the inductor current flow in an alternate path and limit the Back EMF to the forward voltage drop of a silicon diode (0.7V).

Monitor your health with Raspberry Pi & an E-health sensor

You can monitor various health parameters with your Raspberry Pi or RBPi. All you need to do is to use the e-Health Sensor Platform by plugging it atop your RBPi. This arrangement is especially helpful in performing biometric and medical applications where nine different body parameters are to be sensed: oxygen in blood or SPO2, pulse, body temperature, airflow or breathing, electrocardiogram or ECG, galvanic skin response or GSR or Sweating, blood pressure or sphygmomanometer and patient position or accelerometer.

All this information is available in real time, and can be used to monitor the state of health of a patient. The sensitive data can be stored for subsequent analysis for medical diagnosis. Depending on the application, the biometric data gathered can be sent wirelessly over any of the six different connectivity options available: ZigBee, 802.15.4, Bluetooth, GPRS, 3G or Wi-Fi.

For real time image diagnosis, you can attach a camera and send photos and videos of the patient to the medical diagnosis center. For permanent storage, the data can be sent to the Cloud. Visualization in real time is possible by transmitting the data over to a Smartphone or a laptop directly. There are plenty of applications for the iPhone and Android Smartphones that will allow the patient’s information to be seen.

This opens up a new era of open source medical products. The RBPi provides the new e-Health applications and products a quick proof of concept with the necessary tools. However, one of the key points in such applications is privacy and several security levels are provided with the platform.
The communication link layers use WPA2 for Wi-Fi and AES 128 for ZigBee and 802.14.5. The application layer uses a secure protocol (HTTPS) to ensure a point-to-point secure tunnel between the web server and each sensor node. Banks use this type of communication security protocols for their transactions.

The e-Health Sensor Platform is available from Cooking Hacks. Cooking Hacks, the open hardware division of Libelium, have designed it. The platform helps artists, developers and researchers to measure different biometric sensor data for their experimentation, tests or fun purposes. Compared with the expensive and proprietary medical market solutions, Cooking Hacks provides a comparatively cheap and open alternative.

Cooking Hacks also provides an RBPi to Arduino shields connection bridge, which includes the possibility of connecting the analog and digital sensors to both the boards. This allows harnessing the power and capabilities of the RBPi with the pinot of the Arduino. Further, they also have the arduPi library that allows the use of RBPi with the same code that is used for the Arduino. The arduPi library allows wireless modules, sensors, shields and electronic module or actuator to be interchangeably used for both RBPi and the Arduino.

Note: The e-Health Sensor Platform does not yet have a medical certification. Therefore, it must not be used to monitor patients who are critical and who need to be monitored by medical methods that are more accurate or those whose conditions need monitoring for ulterior professional diagnosis.

Cool Technology: a spelling pen!

You might have wished for something to warn you if you misspelled a word while writing a letter or doing a school assignment. Well, help with this is on the way!

A couple of German inventors, Daniel Kaesmacher and Falk Wolsky have developed a prototype of a pen that can warn you when you make a spelling mistake or when you do not write a letter correctly. Going by the name Lernstift, the pen starts to vibrate when the writer makes a mistake while writing out a word or letter. Lernstift is German for the term ‘learning pen’. The spelling pen will certainly not autocorrect your spelling like automated software tools for checking grammar and spelling do on your PC, but it will tip you off when you make a slip-up.

How does it Work

The prototype of the pen makes use of a software program that recognizes movements related to the forms or shapes of each letter. You can use the pen in two modes. In the calligraphy mode, the pen warns you by buzzing when you do not form a letter properly. This is particularly useful for people with messy handwriting. If you use the pen in the orthography mode, it will buzz if you make a spelling error. A non-optical sensor perceives the mistakes.

The Linux minicomputer installed in the spelling pen gets its power from a battery with a Wi-Fi chip. A crucial feature of this writing tool is that the sensor can detect any writing motion. This eliminates the need for a special kind of writing paper. Unlike other similar smart writing tools, which are slowly coming into the market, Lernstift can work on any kind of paper.

The inventors propose to incorporate exchangeable tips or refills. You can choose to write with fountain pen or ball pen refills.

Modifications to Prototype

You would not really expect the developers of this immensely innovative tool to be complacent about their invention. The creators are already looking for ways to check grammar. Wolsky and Kaesmacher expect the pen to go a long way in assisting children to build up their writing skills. The hands-on approach will certainly serve a better purpose than memorizing rules of grammar. Future models may include pencil leads, as well.

Other enhancements proposed by the inventors include pressure sensors and connection to personal computers. You may then connect the pen to your smart phone or PC to upload text files and share them online. The developers also hope to design apps to widen the possibilities of the pen so that it becomes a multi-functional device.

Idea behind the Inspiration

Falk Wolsky got the concept for the pen when he saw his son struggling with spelling issues in his homework. He conceived of the idea that a vibrating pen could warn a writer about a mistake made in written work.

Since writing is an important procedure for learning, Wolsky feels that the pen could be a useful means for young learners to develop language and spelling skills.

This is something we could all use!

Variation of Capacitance of Ceramic Capacitors with Voltage and Temperature

The ceramic capacitors that you work with in the lab have two or more alternating layers of a metal acting as the electrodes and a ceramic acting as the dielectric. The capacitance measured in farad represents the charge stored in a capacitor at a particular applied voltage. The quantity should be a constant for a particular capacitor at all values of applied voltages and temperatures.

Capacitor Categories

While working with Class I capacitors, you may find that their capacitances do not deviate from the expected values. However, Class II and Class III capacitors do show a marked deviation from the rated values. These capacitors have greater volumetric efficiencies, however. This means that they offer higher capacitances compared to the volume occupied by the capacitors.

Identifying Codes

An alphanumeric code of three characters designates the type of a class II capacitor. The first and second characters of the code indicate the lower and upper limits of temperature and the third character specifies the change of capacitance within the range.

Take the case of X7R, which is a popular Class II capacitor. The letter X indicates a lower limit of temperature of -55°C and the number 7 indicates an upper limit of +125°C. The third character R points to a change in the actual capacitance by +/- 15% from the rated value while the device is working within the temperature range defined above.

Deviation of Capacitances

In other words, you can expect that an X7R capacitor of a rated value of 4.7 microfarad might show a capacitance of 3.9 microfarad, while working under these temperature limits. However, it is a common occurrence to find that capacitors in certain circuits show a much more remarkable drop from their rated values. An X7R capacitor can exhibit a drop of 20%. Certain other Class II capacitors may show a drop as significant as 80% of their rated values of capacitances.

The real fact is that the rated capacitance value of a capacitor holds for a particular value of the applied voltage, also called the DC bias voltage. If the bias voltage is different from the specified value, the capacitor will offer a capacitance that is different from the rated value.

For instance, if you choose a capacitor of 4.7 microfarad designed to operate at 16 V, it may offer a capacitance as low as 1.5 microfarad while working at 12 V.

The code used to identify the capacitors does not indicate the exact variation of capacitance with the applied DC bias voltage. However, it is a known fact that Class II capacitors designated by the letter X are the most stable. The capacitors designated by the letter Y are less stable under adverse environmental conditions while the Z capacitors are the least stable.

Material Used

To understand the problem, you need to study the data sheet for capacitors, which indicates the variation of capacitance with the applied bias voltage. The data sheet illustrates another interesting fact regarding capacitor sizes. A larger capacitor offers a greater capacitance at a particular DC bias voltage than a smaller one identified by the same alphanumeric code. Hence, you can expect a better performance with a larger capacitor than with a smaller capacitor of the same code. A possible reason for the fact could be that manufacturers have to compromise on the material while making smaller capacitors of the same code.

How does a smartphone camera autofocus?

How does the camera of a super slim smartphone autofocus?

As long as cell phones were over 10 mm thick, manufacturers had no problem of getting the camera to autofocus. Of the 2 billion cameras manufactured for the phone and tablet market, nearly half of them autofocus. Usually, one of more of the lenses in the camera are moved in or out using a linear actuator, while an algorithm calculates a figure of merit for the sharpness of image for that location of the lens. The best focus for the scene is achieved by repeating this procedure.

This was going fine, until form factors started to get thinner. Manufacturers made thinner phones, and people took this as a paramount design consideration. As the 5 mm form factor was approached, compressing an 8-13 M Pixel auto focus camera that would still produce high fidelity images became a challenge. In addition, the requirement of speed, power and performance also changed, and altogether, forced manufacturers to abandon the old method of Voice Coil Motor in favor of a MEMS linear actuator.

The Voice Coil Motor (VCM) operated using the principle of electromagnetism. This is the same technology used in loudspeakers to produce sound from electricity. When electricity passes through a coil, it produces a magnetic field that reacts with a permanent magnet to either repel or attract the coil. The movement of the coil is restricted such that it can only move along its axis. Springs attached to the coil help to bring it back to its rest position once the electricity in the coil stops flowing.

The main disadvantage of the VCM is the hysteresis of its stroke. Usually, the coil does not return to its original position after a displacement and this prevents rapid tracking of focal distances in a VCM controlled camera lens. Other disadvantages are the high requirement of power for operating the VCM and de-centering and lens-tilting while operating. All these problems became increasingly acute with increasing image sensor resolution, decreasing pixel dimensions and f-numbers. Moreover, with the VCM technology now over 100 years old, the opportunities for further cost reduction are virtually nil.

This paved the way for a competing technology with a commercial opportunity that can deliver improved performance at a reasonable cost. This is the MEMS or Micro-Electro-Mechanical-System that uses components from one to 100 micrometers in size.

The MEMS technology for autofocus integrates the three functions of a linear actuator. It provides a linear vertical movement, has a spring to provide the restoring force and uses an electrostatic comb as a drive to displace the lens. The MEMS technology saves on power since it does not use electromagnetism.

The comb drive is more like interlocking fingers, only the fingers never touch. The electrostatic charge developed when a DC voltage is applied, develops an attractive force causing the combs to be drawn to each other. The lens, which is attached in the center, completes the silicon MEMS autofocus actuator.

The MEMS technology allows only one lens to move very precisely, while the other lenses are locked in the most optimal position. This approach offers an excellent image quality over the entire focal range within the 5 mm allowed in a thin smartphone.

All about Fritzing

Fritzing is a software program to help designers translate their prototypes into real products. Created at the University of Applied Sciences, Potsdam, the software is an open source software tool. It runs on Linux, Mac OS X and MS Windows.

The Open Source Idea

The term open source in software development indicates an approach that provides any individual access to the design of a product or improvements made to it. The Internet has made the concept of open source more viable.
In an open source program, any individual may open or unlock the source code. An innovative programmer may even make modifications to the code in an attempt to improve upon it.

Concepts behind Fritzing

To understand Fritzing, it is important to know something about Breadboard View, Schematics View, and Printed Circuit Boards View.

Breadboard View – Fritzing can present your circuit in breadboard view, making it easy to visualize how components will fit together and be wired together. Fritzing has a vast library of parts to represent all major components in the Breadboard view.

Schematic View – This is the traditional view of the circuit as represented in books. Frtizing has a large library of schematic parts to build up the Schematic View.

Printed Circuit Board View – A printed circuit board (PCB) consists of electronic components connected electrically on copper tracks laminated on a non-conducting substrate. This view is necessary to fabricate the PCB for the circuit.

Purpose of Fritzing

The software program allows designers and other professionals to record their prototypes created for various circuits and design corresponding PCBs. You can use the company website to communicate your ideas and drafts with other individuals. Others may create electronic items based on your prototypes. This concept of sharing helps reduce production costs.

One of the great advantages of Fritzing is amateur electronics enthusiasts can design circuits and build PCBs suited to their needs. All the gear needed is available from the Fritzing store.

You can even play with the Raspberry Pi using Fritzing. The rapidly growing Fritzing library now features the Raspberry Pi Model B!

Making your own PCB

You can design and create a printed circuit board using the Fritzing software.
Print your circuit diagram onto a sheet of glossy photographic paper using a laser printer. Place the sheet on a copper board with the printed side facing the board. Run a hot clothes iron over the sheet. If you have done the job well, you should get a clear etching of the circuit on the board. You may need to clear away the excess copper with a Ferric Chloride solution.

Be careful with the Ferric Chloride solution as this is a very corrosive liquid and will eat through most clothing and skin. Wearing a PVC apron, gloves and PVC shoes is recommended when working with Ferric Chloride.

The Fritzing software company provides a service called the Fritzing Fab. You will have to upload your file, place your order and make the payment. At the time of placing your order, you can request extra services like punching holes for mounting the board. The company will deliver your printed circuit board in about two weeks.

4 Accessories to Turn your Raspberry Pi into a Workhorse!

Gert Board To Pair Up Your Raspberry Pi With The ATmega Microcontroller

You can now expand the General Purpose Input Output (GPIO) pins of your Raspberry Pi with a Gert Board. Gert Board is the brainchild of Gert Van Loo, one of the developers of the alpha version of the Raspberry Pi. With the addition of the 28-pin ATmega microcontroller, you have the entire Arduino Integrated Development Environment (IDE) at your disposal. Moreover, it is possible to add any of the following ATmega controller models to the Raspberry Pi – ATmega 48A/PA, ATmega 88A/PA, ATmega 168A/PA or the ATmega 328A/PA.

So, what does this mean for your Raspberry Pi? By adding the Gert Board, you get an 18V @ 2A port for your motor projects. You also get a 2-channel, 8-, 10- or 12-bit Digital to Analog converter along with a 2-channel 10-bit Analog to Digital converter. Additionally, you get 6-Open Collector drivers capable of 50V @ 0.5A, 12-Buffered I/O’s and three push buttons.

PiFace Digital Controller

If you intend to control external hardware via the Raspberry Pi’s GPIO header, the easiest way is to use the PiFace Digital developed by Andrew Robinson of the University of Manchester. The PiFace Digital has two onboard changeover relays, and this is the central feature of the add-on board. The changeover relays have open-and-close positions, which are accessible to the user. Each open-and-close position of the relay can handle 5V @ 10A maximum. You can program the board through Python, C or Scratch. Scratch has also developed an emulator, called the PiFace Emulator. This gives you a graphical control over the features of PiFace. Not only this, PiFace has additional onboard features such as eight digital inputs., eight open-collector outputs on connectors, eight LED indicator lights on the outputs and four tactile switches.

Pi Camera

The Raspberry Pi has an onboard CSI port, which you can connect using a ribbon cable to the Camera Module. The Raspberry Pi camera module measures only 25mm x 20mm x 9mm. The tiny module has an Omnivision 5647 fixed-focus module that can handle 5MP still images, while weighing only 3 gm. You must use a 4GB or larger SD Card on your Raspberry Pi, as this is where the images from the camera are stored. The camera can handle resolutions of 1080p30 (1080 pixels at 30 frames per second), 720p60, and 480p60/90. The CSI bus on the Raspberry Pi is capable of handling high data rates streamed directly to the processor on board (BCM2835 ARM 11).

A Slice of Pi

This breakout board, called the Slice of Pi, is the least expensive of all the expansion boards for the Raspberry Pi. The board has a serial peripheral IO port expander, MCP23017, which adds 16-input/output channels to your Raspberry Pi. Apart from this unique feature, you can also use the board as a custom development area. One key feature of this Slice of Pi is the Xbee style connector mounts. Since this can support the XRF, Xbee and the RN-XV wireless modules, the functionality definitely expands the popularity of the board. Apart from this, you have easy access to the on-board GPIO, the 3V3, 5V; GND and the TX/RX solder points.

Digital Isolators vs Optocouplers

Industrial equipment may need to operate in a region of strong electromagnetic fields. There can be a sudden surge in the voltage applied to the equipment, which may be hazardous to the user and the gear. It is crucial that you incorporate a reliable isolation system to take of these issues.

Until very recently, the optocoupler was the only practical choice in providing safety isolation for manufacturers of medical and industrial isolated systems. The arrival of digital isolator has however, changed the situation greatly.

Digital isolators offer several advantages over optocouplers. They are more reliable, cheaper and have greater power efficiency compared to the optocouplers.

It is important that you understand the three vital aspects of an isolation system. These are the insulation material, the structure and the method of transfer of data.

Insulation Material

Typical insulation materials are silicon dioxide wafers and thin film of polymers. Optocouplers use polymer films. Digital isolators make use of a particular form of polymer called polyimide. This material serves to increase the efficiency of isolation systems.

Silicon Dioxide is not a very suitable material as an isolator. While you may increase the thickness of polyimide to increase the insulation, you cannot adopt the same method for silicon dioxide. Wafers thicker than 15 micrometers may crack during processing.

Structure

Digital isolators use either transformers or capacitors to transfer data across the isolation barrier. A transformer system has two coils placed side by side. Current flowing through a coil (called the primary coil) gives rise to a magnetic field in the space surrounding the coil. This induces a current to flow in the other coil (called the secondary coil).

A capacitor consists of two metal plates with the space between the plates filled with a non-conductor.

Optocouplers use light emitting diodes (LED) for data transmission.

Transfer of Data

The LED in an optocoupler turns on for logic high state and turns off for logic low state. The device consumes a significant amount of power when the LED is on. Digital isolators do away with this undesirable aspect. The sophisticated circuitry in the system encodes and decodes data at a rapid pace so that the transmission of data involves less power consumption.

A digital isolator using a transformer for data transmission transfers the data from the primary coil to the secondary coil during the pulses of current driving the transformer.

A digital isolator may use radio frequency signals as well, in a fashion similar to the way an optocoupler uses light from an LED. However, since a logic high state causes a continuous transmission of radio frequency signals, this method uses more power.

Digital isolators with capacitors have an advantage in that they consume lower currents for creating coupling electric fields for data transmission.

Ensuring the Correct Combination

It is important to use the right insulating material and the apt method for data transfer depending upon the application.

Since polymers provide more than adequate insulation, they are suitable in most applications. Polyimide insulation is particularly suitable for equipment used in healthcare and heavy industries.

Concerning data transfer, capacitor isolation is adequate for situations requiring just functional and not safety isolation. Isolation systems making use of transformers will serve the purpose of safety as well as functional isolation.

The Emergence of BBB: the BeagleBone Black

Many a time we have wished our bulky PCs that occupy so much of the desktop space could somehow be magically squeezed into a portable unit. Although such systems are there including the new smartphones and tablets, their sky-high prices are very discouraging for most of us.

Despair not, for such a package has arrived and is well within the reach of an average person’s pocket. Moreover, if you are technically oriented, you could build one yourself. Texas Instruments has provided the core processor and BeagleBoard has provided the packaging. The result is the low-cost, low power, fan-less, single-board computer called the BeagleBone, a latest addition to the BeagleBoard family.

The low-cost, fan-less, low power, single-board computers from BeagleBoard utilize the Texas Instruments’ OMAP3530 application processor. This offers laptop like performance and facility for expansion, without the bulk, the noise and the expense that are typical of desktop machines. Within the OMAP3530, there is a 600MHz ARM Cortex-A8 Micro Controller Unit (MCU), which predicts branches with high accuracy and a 256KB L2 cache memory.

The on-board USB 2.0 OTG port serves a dual purpose; you can transfer data out from the board or allow the board to read data in from an external source. Although the board has a separate 5V DC power socket, power to the board can be supplied through the USB port as well. The board also has a mini-A connector, to which you can connect standard PC peripherals using a standard-A to mini-A cable adapter. A DVI-D connector allows a HDMI display to be connected using a HDMI to DVI-D adapter. The third connector is the MMC/SD/SDIO card connector. To give you the best graphics experience, the BeageBoard has a state of the art POWERVR graphics hardware, which will render 10 million polygons each second.

For people who were not satisfied with the power of the BeagleBoard single-board computer, BeagleBoard has added the BeagleBone Black or BBB. This is the newest addition to the BeagleBoard family, and continues the saga of the low-cost, low power, single-board computers. To provide the additional features, an advanced MCU, the Texas Instruments’ Sitara AM3359 has been used. This is an ARM Cortex-A8 32-bit RISC processor, featuring a speed of 1GHz, and gives BBB the power along with a 512-MB DDR3L 400MHz SDRAM and 2GB 8-bit eMMC on-board flash memory. This frees up the micro SD card slot for further expansions.

The 92-pin headers are Cape compatible, meaning the existing family of cape plug-in boards can be used as well. The on-board HDMI allows direct connection to monitors and TVs. External electronics circuitry can be controlled by the UART0 serial port. For connecting to the Internet, a 10/100 RJ45 Ethernet connector has been provided.

You will need the latest Angstrom distribution eMMC flasher to load the latest Linux distribution. This is a 4GB image, that has to be uncompressed using unxz and written to a micro SD card. Connect an HDMI monitor, and after plugging in the micro SD card in the slot of the BBB, you can power on your single-board Linux computer. Take care to hold the boot button on while powering, and watch the LEDs on the BBB flash and then stay on.