Author Archives: Andi

How to select the best inductor

A good understanding of the desired in-circuit performance is required for a proper selection of an inductor. Fortunately, this relates to the information available in data sheets supplied by the manufacturer.

Any electronic equipment needs power to operate satisfactorily. Portable instruments invariably use dc-to-dc converters for generating the required voltages from power sources such as batteries. Additionally, as equipment size reduces, so does the need for optimizing inner parts, especially the power conversion solutions; it is no longer possible to stick on to the “one size fits all” approach. For example, manufacturers are producing low profile components, which are proving to be very popular.

Inductance is the primary functional parameter that defines an inductor. This value, calculated by the converter design equations, determines the ability of the inductor to handle the desired output power and control the ripple current in a dc-dc converter. However, specifying the inductance value alone is not sufficient for defining the required inductor. You also need to specify the DCR, SRF, Isat and Imms for a complete specification.

The DCR or the DC resistance of an inductor depends on the length and diameter of the wire used in manufacturing. The power dissipated by the inductor depends on the DCR. Therefore, if the inductor were to be used in an enclosed space, a lower value for the DCR would certainly be an advantage. Please note, resistance offered and hence power dissipated at high frequencies usually depends not on DCR, but on skin effect.

Another important factor is the SRF or the Self-Resonant Frequency of the inductor. At this frequency, an inductor begins to resonate naturally, using the distributed capacitance characteristic of the winding. In a dc-dc converter, SRF might cause unwanted oscillations and lead to instability of the output. The manufacturer specifies the SRF and it depends on the nature of the construction. The designer usually selects an inductor with an SRF that does lies outside the operating frequency range of the application.

Inductors with cores are liable to saturate. When in saturation, the inductance value falls drastically, upsetting the operation of the dc-dc converter. Isat or the Saturation Current, specified by the manufacturer is therefore, an important parameter, which states the amount of current that would cause saturation and subsequently a fall in the inductance value. Designers need to select an inductor that has an Isat value larger than the maximum currents expected in the converter.

Power dissipation in an inductor is dependent on two factors – the DCR and the Irms or the RMS Current flowing through it. Manufacturers specify the maximum rms currents that the inductor can handle causing a specified temperature rise. Therefore, the designer has to select an inductor whose Irms value is larger than the maximum rms currents that the converter is expected to deliver.

Fortunately, dc-dc converters are rather forgiving towards tolerances of inductors. These applications do not require inductors to have extremely tight tolerances to achieve their outputs. Standard tolerances indicated by manufacturers are +/-20%, which most converter designs accept as suitable.

Resurrecting a dead horse? Windows XP

Now that it has been officially announced that there will be no more updates from Microsoft for the workhorse of the industry – Windows XP. The popular and widely used operating system started its life in October 2001. Within the first five years of its availability, officially sold copies outnumbered 400 million. By the time Microsoft withdrew support, in April 2014, the sales figure stood at 1 billion. Add to that the use of another few billion pirated copies all over the world, and you start to get a fairly good estimate of the software’s popularity.

Apart from the popularity, Windows XP figured in several industrially used computers as well, for example, Automatic Teller Machines or ATMs, Point of Sales or POS machines and several types of machine and laboratory instrument controllers. With the withdrawal of active support from Microsoft, the software will not be updated or upgraded, leaving it exposed to exploitation by unscrupulous attackers.

For example, the recent vulnerability exposed in the Internet Explorer, the browser used in almost all Windows OSs, left many wondering about the fate of XP. Fortunately, Microsoft stepped in with the assurance that it will provide a patch for the IE vulnerability for XP. However, Microsoft is unlikely to tackle any further vulnerability discovered subsequently in Windows XP.

However, the situation may not be as hopeless as it sounds. Switching over to Windows 7 or 8 may not be within everyone’s reach, especially when there are several underlying programs working within that depend on Windows XP for their proper operation. Shifting to Windows 7 or 8 might break the functionality of the instrument.

Linux can come to the rescue of such equipment left in the lurch by Microsoft. We are already using Android and Apple phones and computers, both of which are derivatives of the UNIX operating system. Linux is another popular operating system based on UNIX. The best part is you can run any Windows programs in Linux under a virtual mode. The advantage is you do not need to bother about the vulnerabilities of XP, as Linux extends all its inherent security to the operating system used under its virtual mode.

For this, John Martinson has configured a special version of Linux, called the Robolinux. It has a specially formulated virtual mode called the Stealth VM. When you run Windows within this virtual mode, no virus or malware can affect Windows or its data, since the Windows operating system is actually a protected clone and Linux mirrors your data within a secure partition. Additionally, with anything going wrong, you can simply restore the contents of the partition within a few minutes, instead of having to spend hours resurrecting Windows from its CD/DVD.

It is not strictly necessary to run Robolinux for using Stealth VM, as you can run this within any of the existing 500 Linux Operating Systems. If you want to run Windows XP or 7 within your Stealth VM, you simply download the Robolinux Virtual Machine installers. You get the rock-like solidity of UNIX and Linux, including complete protection from viruses and malware when running your coveted Windows XP.

A smartphone built from Raspberry Pi: the PiPhone

You may not be looking for a new cell phone right now, but someone has just managed to transform his Raspberry Pi (RBPi) into a working cell phone. David Hunt has used only off-the-shelf components and put them together for the project. Although it is not as slick as the regular cell phones available in the market, at about $160, David has created a one-off project that certainly has no economics of scale working for it. The best part is all components of the phone can be taken apart at any time, used for some other projects and then reassembled. Can you do that with your regular cell phone?

David has called his cell phone the PiPhone, in honor of the base RBPi that powers it. The other major parts used for making the PiPhone work are a Sim900 GSM/GPRS module and an Adafruit touchscreen interface. The GSM/ GPRS module allows the cell phone to make and receive calls, while the touchscreen provides the user interface. A 2500 mAh LiPo battery powers the entire contraption. The GSM module connects to the RBPi through a UART, while the battery fits in between the TFT screen and the RBPi, allowing the PiPhone to work standalone, without wall warts or dangling wires.

The touchscreen interface has a numeric keypad displayed on the screen. After dialing the required number, you need to touch the phone icon at the bottom to make the call or hang up.

The Sim900 GSM/GPRS is an intelligent module, which oversees the entire communication process of the PiPhone, including sending the standard AT commands to the RBPi for making calls, hanging up and sending text messages or data. Towards the bottom of the PCB is the connector where you can insert your SIM card. Therefore, you can use a regular prepaid SIM card available in the local phone store.

Just below the GSM module, there is an on/off switch and an off-the-shelf standard DC-DC converter. This converts the 3.7V supplied by the battery to the 5V required by the rest of the electronics. Heat dissipation was the only problem that David faced because of sandwiching the RBPi, the TFT, battery and the GPS module together. During development, as all the components were placed apart, they remained cool to the touch even after extended periods of use. However, sandwiching prevents air from circulating within, resulting in the CPU getting a bit warm after switching the unit on for a few minutes.

The GPS card is insulated from the RBPi with a thick foam-core board, allowing no accidental electrical connections between them. David used a couple of cable-ties to hold the different parts together.

Of course, walking into a local phone shop and picking up a normal smartphone would be simpler and cheaper, but that would not be as much fun as making your own. Moreover, as said earlier, you can put the parts to other uses as well, which you cannot do with a standard phone.

David has put up all his code and instructions on the GitHub. There are links available to instructions on installing the TFT.

What is Human Machine Interface: HMI?

Accelerating quality, quantity, economic efficiencies and environmental protection are leading to an increasingly connected process flow and factory floor. In combination with decreased personnel, that has led to processing of increased amounts of information by fewer and less application-specific operators in the control center. It requires a well-designed HMI or Human Machine Interface system to decrease the gap between the production process and the operator via an intuitive visualization system, layers of detail that allow a bird’s eye view down to the minute details, and includes training material and documentation that the operator has on his fingertips.

A well-designed HMI system provides numerous benefits. Chief among them are increased safety, quantity, quality and economic efficiency. Apart from minimizing the risk of disruption in the production process, HMI systems also reduce the over downtime while allowing fewer operators to manage more information with less field-specific knowledge.

HMI provides a means of monitoring, controlling, managing and/or visualizing device processes. For example, an operator panel may allow the operator of an industrial machine to interact with the machine in a visual, graphical way. The operator can easily control the machine by using the touch screen or external buttons, as all readouts and controls readouts are graphically displayed on the screen.

HMIs can be located on the machine, in the form of simple segmented displays or LCD panels of high-resolution. They can be located in portable handheld devices that are battery operated or in centralized control rooms. Machines and process controls can use them to connect the operator with Programmable Logic Control application systems to control sensors, actuators and machines on the factory floor.

For communicating with industrial machines, the usability of the HMI system depends on the processing power of the system, its ability to render reality-like complex screens, quick responses to user inputs and the flexibility for handling several levels of operator interactions. Usually, effective communication requires the HMI to have dynamically changing graphics. This in turn, requires the system to be a high-performance type that supports various resolutions and displays of high refresh rates. For efficient communication between the operator, numerous machines and control systems, it is imperative that multiple connectivity and protocols must be supported.

Industrial automation thrives on real-time communication. Using industrial micro-controllers along with PRU-ICSS or programmable industrial communication subsystems makes it possible to support various popular, certified serial protocols, including those that are Ethernet-based. The PRU-ICSS allows HMI manufacturers easily support industrial communication protocols of multiple types on a single hardware platform. The most important advantage of this platform is that it does not require the support of external ASICs and FPGAs. This offers huge scaling in performance and the integration offers opportunities of software and design reuse.

Portable HMI solutions use several wireless connectivity solutions such as WLAN, Sub-1GHz, ZigBee and BlueTooth. This broad portfolio offers the maximum flexibility when designing for wireless. For example, the WiLink 8 solution provides high-performance BlueTooth and Wi-Fi in one module. The Sub-1GHz performance line is very popular and the most reliable in its range.

DC-DC converter with increased efficiency & reduced noise

The new Synchronous Buck-Boost DC/DC converter LTC3111 available from Linear Technology is very significant in many respects. The most important factor being that it is able to operate at 95% efficiency and that too at a very low noise level. It can give a power output of 1.5A when used from a very wide range of power sources. These include multiple or single cell batteries, wall adapter and super-capacitor stacks. This convertor accepts 2.5 to 15V as the input and outputs 5V with the regulated output converted at almost 95% efficiency. Its noise reduction technology ensures that LTC3111 operates at a reduced level on a continuous basis at both buck or boost transitions. This convertor is considered ideal for all applications that require power output at a constant level without noise when the input is varying.

In many areas of operation, where battery life is to be extended by step down solutions, this convertor offers a straightforward solution. This is done by synchronizing the default 800KHz frequency to an external 600 KHz to 1.5 MHz clock. LTC3111 has a proprietary feature of the third generation that gives maximum efficiency at a very low noise level. That reduces the use of external components, which makes the solution offered extremely compact in all respects.

The LTC3111 has four N-channel MOSFETs with very low on-state resistance and the efficiency of 95% is achieved with the use of a single inductor. The Burst Mode is user selectable and this operation impressively lowers the quiescent current down to only 49µA. That enhances the light-load efficiency and significantly improves the battery run time. The burst mode has the option of being disabled whenever the operation is for noise sensitive applications. The output can be disconnected from the load; it has over voltage protection and short circuit protection. A thermal shutdown feature is one of the main advantages of this LTC3111 convertor.

These converters are offered in the market with several variations in packaging. The 14-lead 3mmx4mm DFN package is identified as LTC 3111EDE. Thermally enhanced 16 lead packages are also available and identified as LTC3111MSE. The pricing has been kept competitive. The industrial grade component with an operating junction temperature range of -40 to 125°C is priced slightly on the higher side. Further, higher operating temperature convertors that range from -40 to 150°C are also being offered at special prices. The same converter versions with high reliability are also on offer. Their operating temperature range is from -55 to 150°C. Most significantly, all the versions are available for immediate shipping and discounts are given for bulk quantities.

Notably, the Synchronous Buck-Boost DC/DC converter LTC3111 launched by Linear Technology is significant for both industrial and domestic applications. It is able to achieve an optimum output of 95%, even when the power input is from different sources. The noise level is also considerably reduced as compared to other similar products in the market. This converter is the answer for optimum performance for all noise-sensitive applications. With ready-to-ship availability, this product will find a number of users.

Cubli the Baron Munchausen of Robots

When you find a cube lying innocently on the table, you wouldn’t exactly expect it to jump up and start balancing itself on its edge or on its corner, will you? Probably not, if it wasn’t Cubli, the one designed at ETH Zurich. Well, it does not actually lift itself up by its own locks as Baron Munchausen was fond of doing, but Cubli the robo-cube can bring a smile on your face when you see its capers – watch its antics below.

Cubli, the 15x15x15 cm cube, has several spinning wheels and motors inside it. The contraption lets Cubli lie on one of its sides peacefully, then jump up to stand on an edge and proceed to tilt for balancing itself on one of its corners. By combining its jumping and balancing tricks, Cubli can even walk!

A closer inspection reveals three reaction wheels within the cube, one on each axis. These are able to spin at high speeds, as they have a motor each to drive them. The combined reaction of the three spinning wheels makes Cubli attain its uniquely stable postures. In fact, the positions are so stable that you can even nudge Cubli a little and it will resist falling over. Cubli can control its fall, allowing it to “walk” on a surface.

To control the speed of each of its wheels, Cubli has three motor-controllers, governed by an on-board processor and a bevy of inertial sensors. The motor-controllers rev up their individual motors based on the commands from the processor. Sensors monitor the tilt and angular velocity of Cubli at different points and feed this data to the processor to compute how fast each of its reaction wheels needs to spin to get Cubli to maintain its position.

By suddenly stopping the spinning of one of its reaction wheels, Cubli can jump up to one of its edges from its resting position and similarly, proceed to balance itself on its corner. Satellites use the same technique to keep themselves stable in orbit and Segway keeps you from falling off its scooter. However, the algorithms that Cubli uses are entirely different.

It feels funny watching Cubli walking. From its resting position, it rears itself up on its edge, hangs there for a moment and then gradually lowers itself on to the next side, repeating this sequence for its controlled walk. When Cubli is balancing on its edge or its corner, it will maintain its balance even if you tilt the surface on which it is resting.

All this is made possible because the spinning wheels act as gyroscopes. The momentum of the spinning wheels keeps the cube balanced. When one of the wheels slows down, it loses its momentum, and the center of gravity of the cube starts to pull it down. Speeding up the wheel improves the momentum and counterbalances its center of gravity, allowing Cubli to regain its position.

Another research group is considering using this amazing technology for building robots and using them for exploring other planets.

Haptics: A sense of touch through the computer screen

Touch-screens are quite common in mobiles, smartphones and tablet computers nowadays. They allow us to control and command the computer according to our requirement. A sense of touch is something different; it is sensing an object displayed on your computer screen. Imagine seeing a rose on your computer screen and by reaching out with your fingers, feel the softness of its petals.

This amazing possibility is the result of a non-mechanical haptic interface that allows computer users to manipulate a three-dimensional object on the screen of a computer to receive tactile response from the surroundings of the object. In short, you can reach out to touch and feel the object displayed on your computer.

The haptic interface uses flotor, a device shaped like an inverted umbrella and it contains coils of wire. It also has a control handle, which the user moves to interact with powerful magnets underneath. Electronic circuitry transfers the motion on to the screen that responds when an object collides with anything in the virtual world.

Normally, you are able to see and hear the information displayed on your computer screen. Touching the image to feel its texture and movement was not an option until now. At Carnegie Mellon University of Pittsburgh, PA, Dr. Ralph Hollis is working on his specialization, haptics – the science and technology of touch.

The user has to grasp a handle inside a sphere that is attached to a desktop computer. The handle connects to an object that looks more like an upside-down umbrella and it is called a flotor. The flotor carries electrical current flowing through electrical coils. All this is immersed in a powerful magnetic field, created by several permanent magnets.

Normally, the magnetic field allows the handle to float freely inside the sphere. The user can move and rotate the handle to control the position of a 3-D object on the computer screen. As soon as the object touches something in the virtual world, the user can immediately feel it.

Although there are many other haptic devices around, the concept of grabbing a motorized arm to interact with the computer is unique. Dr. Hollis has used magnetic levitation to make a direct connection between the user’s hand and the software. The result is direct and immediate feedback.

Briefly, haptics brings touch within a digital environment. This may give you the feel of resistance when you use a joystick in a game or give you touch sensation when using gloves in a virtual reality environment. Using haptics, the user gets an instant feedback when an object collides with another and does not have to rely only on what he sees. You can estimate what it feels like when you have to walk when your foot has fallen asleep. Adding the feeling of touch to a virtual environment makes interactions more life-like and similar to the benefit you have when you have full feeling in your feet.

At present, haptics works only with objects that are magnetic by nature, that is, objects attracted by magnets.

Using the Texy’s Mini TFT Screen for Your Raspberry Pi

The single board computer, the Raspberry Pi (RBPi) is a wonderful device, but it needs a screen for you to see what it is doing. The Mini TFT screen from Texy’s is just made for the RBPi and the kit comes in a beautiful Perspex box too, which makes it very smart and practical. The Perspex box has a neat slot in the corner for the RBPi-Camera, although you may have to add blu-tack to prevent the camera from popping out. The screen and display are pre-built and ready to plug into the RBPi GPIO socket.

The display is backlit TFT, measuring 2.8-inches. The resolution is 320×240, which is a quarter VGA or QVGA, with 64 thousand colors. The current consumption is a mere 99mA. A major portion of this current is on account the backlight, which consumes 85mA. That means, if you switch the backlight off, by setting P1 on Pin18 to low, this screen uses only 19mA, which is great for battery-powered applications.

If you compare this with the 9-inch DVD player screen, which is 640×220 in resolution, and runs from the RBPi Analog output, the Texy’s screen is much sharper and more usable. Note that the standard TV resolution is 720×480 or 720×576. The digital connection makes the RBPi desktop very clear, perfectly formed and very easy to read on the small TFT screen.

The Texy’s screen provides a useful terminal display, fully displaying the entire RBPi desktop. Although it may not run full speed frame-rates, the display shows video perfectly. The compact fonts get a lot of text displayed on the terminal despite it being only 2.8-inches.

The addition of the resistive touch screen is the magical bonus as this opens up a great multitude of project possibilities, where a mouse, full keyboard and display setup would be rather impractical. You can bring the touch panel alive by combining some python code and Tkinter to get a very effective touch-based control system for your RBPi.

Texy’s has added flexibility to the screen in the form of the PI header pass-through available on the display board. You can use a ribbon cable to link the display to the RBPi GPIO and use the GPIO connections on the underside of the display. Alternately, you can connect the display directly to the RBPi GPIO and extend the GPIO with the cable.

Since the display uses SPI interface pins on the GPIO, including CE0, CE1, GPI00, GPI01 and GPI06. The GPIO pass-through allows you to connect your own ribbon cable to add further hardware, which can use the rest of the GPIO pins. A convenient GPIO pin out key is printed on the board for reference.

The easiest option for most is to use pre-configured images for driving the Texy’s display. Others, who are more confident, can modify the existing OS to use the screen; it is suggested to make a backup before setting out. Follow instructions here.

The display case, while providing support to the display unit, also extends out providing protection to the SD-Card while allowing full access to all sockets and connections of the RBPi.

Use your Raspberry Pi as a Hi-Fi Player

If you use your Raspberry Pi (RBPi) in combination with a USB DAC and RuneAudio, it will become a Hi-Fi music player providing surprising sound quality. RuneAudio is a free and open source software that you can use with the single board computer for running the custom-built Linux distribution. The RuneAudio and RBPi combination replaces the PC or the laptop that you normally use as a digital source for music.

Like other open source projects, RuneAudio also came to be born due to personal needs. The developers were not very happy about having to use the laptop as a digital source, its absolute sound quality and ease of use. They started the RuneAudio project and encouraged people to download it, try it free and contribute to the development.

Project RuneAudio has two distinctive goals: One, to provide exceptional sound quality and two, make it easy to use for everyone. The developers are using the RBPi and other supported platforms for deriving the best results. For this, they are using Arch Linux as the base for their RuneOS and optimizing it as best as possible for audio reproduction.

For making project RuneAudio easy to use for everyone, the developers have built a handy web interface – RuneUI, that lets users control the playback and system settings, without any need for touching the Linux command line. With a cross-platform web-interface, the responsive RuneUI adapts to the screen size automatically. That makes it accessible from all types of devices, whether you are using a PC, notebook, tablet or a smartphone. All you need to do for installing is to write an image file to your SD card.

To install, first you will have to download the latest RuneAudio image for your RBPi from the official webpage. Next, extract the contents of the zipped file with a utility for manipulating compressed files such as Unzip on Linux, Zipeg on Mac or 7-Zip on Windows. That will leave you with a raw disk image file (an extension of .img).

The raw disk image file has to be written onto an SD card. You may follow these guides on elinux.org: Linux howto, Mac howto and Windows howto. Before you plug-in the SD card into your device, make sure the card’s write-protection is turned off. After the card has finished writing, unmount it safely and plug it into your RBPi.

Plug-in a USB DAC into the RBPi USB port (you can simply plug in the analog jack if you do not have a USB DAC). You can also plug-in your USB storage or your USB hard drive. If you are using a hub for the USB devices, it is strongly suggested that you use an external power supply for it. Now plug-in your Ethernet connector, plug-in the power supply unit of the RBPi power it on.

That’s all. RuneAudio boots up your RBPi for the first time, and acquires an IP address. Open a web browser on your Android mobile and run RuneAudio from http://runeaudio.local. You should be in RuneUI now. If you want to see this being done, you can view the videos that can be found online.

Ultra-dimmable first retrofit premium 850 lumens LED lamps

Ledzworld, the Netherlands Company based in Amsterdam, has launched the world’s first ultra-dimmable retrofit LED lamp producing 850 Lumens from a single source. The product AR-111 LED lamp has been developed with several notable features incorporated with the user in mind. Ledzworld is a world-renowned company that has been a pioneer in harnessing LED technology and it is no surprise that they have come out with these LED lamps to be used in various places. This innovation is considered as an ideal replacement for the halogen lamps that has been in use for a long time now. The AR-111 LED lamp is well tested, cost effective, highly efficient and the design is perfect for the user, makers, designers and installers.

AR-111 is a single source LED lamp that comes with a CRI of 80. It is also offered with a CRI of >90. It also has the company’s special Chameleon Driver, which is a technological breakthrough that has the self-adjusting feature to make it a perfect fit. It can be used with a variety of combination of drivers and dimmers. The Chameleon Driver detects the transformer type initially and then it goes on to analyze the waveforms to suitably change or transform itself into a perfect fit.

Jan Kemeling is the founder and the Chief Sales and Marketing Officer of Ledzworld. He says, “A large number of current luminaires on the market with integrated LED light engines look bulky, but Ledzworld’s unique AR-111 Platinum Ultra Dimmable LED has the appearance and characteristics of a sophisticated track-luminaire while efficiently delivering 850 Lumens.” The looks are aesthetic and match perfectly with the ambience of museums, lounges, hospitals, hotel, residential, retail displays and restaurants. Kemeling also opines, “This innovative Chameleon Driver makes our AR-111 Platinum LED lamp a true ‘plug and play’ solution that can be trusted with no surprises or disappointments.”

The AR-111 has the intelligence to monitor the temperature within its driver compartment. The beam angle can be adjusted to 25 degrees or to 40 degrees, with the help of Reduced Glare Optical Technology developed by the company. The lamp comes with three-color temperatures of 2700K, 3000K, and 4000K. It has an overall dimension of 62×111 mm with light of single focus. When compared with halogen lamps, AR-111 allows a saving of 80% of the energy consumed. The removable outer ring is patented for the product and it allows the option of matching the color to the application or fixture. Ledzworld offers a three-year warranty for continued usage of this LED lamp.

Given the company’s global reputation in manufacturing LED lamps, this ultra-dimmable AR-111 LED lamp is bound to play a path-breaking role in its use. It offers several benefits by way of energy saving, operational efficiency, convenience in use along with its robust features. The most important aspect of the product is that it is a replacement for halogen lamps that are still used very widely. This effectively means that users gain cost wise as well in its operational efficiency.