Monthly Archives: July 2016

Cool your Raspberry Pi with PiCoolFan

Applications for the single board computer, the Raspberry Pi or RBPi are exponentially increasing and there is a great demand on the RBPI for extending its performance to the limits. While users try to push their RBPi to achieve higher results with overclocking, this may result in SBC frying itself, unless the CPU temperature is kept in check.

To enable complete control over the CPU temperature, an advanced cooling fan system is available – PiCoolFan. On the bonus side, the system also includes a Real Time Clock that RBPi does not have in-built. Therefore, if your RBPi is running hot, for whatever reasons, you can use the PiCoolFan to keep its CPU cool. The applicability extends to all models of the RBPi.

The cooling fan does not require any additional power supply to operate. It draws its power from two GPIO pins. You simply have to insert the connector on the PiCoolFan on top of the P1 connector of the RBPi. A dedicated sensor on the PiCoolFan continuously senses the PCB temperature of the RBPi, feeding the readings to an embedded temperature measurement system on the PiCoolFan. Depending on the measured temperature, the micro-controller on-board the PiCoolFan will start, stop or regulate the rotational speed of the tiny fan.

As an added advantage, PiCoolFan contains an Air Distribution Plate, which cools not only the microprocessor on the RBPi board, but also all the heat-generating devices and the entire RBPi PCB. The RBPi user can easily access the embedded micro-controller on the PiCoolFan via the I2C interface. Apart from being able to read the temperature measured, the user can also set the temperature threshold and the temperatures at which the micro-fan will start and stop.

The PiCoolFan also offers on the same board a real time powering voltage monitoring and a real time clock with full battery backup. The entire unit is small enough to be included within most of the already existing cases of the RBPi. Apart from reading the temperature via I2C interface, PiCoolFan offers the user an information system based on three LEDs. A glowing blue LED assures the user the RBPi is comfortably within the allowed operating temperature range. If the temperature exceeds the range, the red LED will start to glow.

A flashing green LED indicates the powering status. When the voltage is within threshold limits, the flashes are continuous. When higher than the threshold, the frequency of the flashes increases. If the voltage is below the threshold limit, the frequency of the flashes decreases. Therefore, with a transparent case, it is easy to see from a distance whether the temperature and voltage of the RBPi system is within specified limits.

The user has complete control over the PiCoolFan system via the I2C interface. The fan can be switched on or off unconditionally and its speed controlled by pulse width modulation or PWM. The user can read the current system temperature and set the temperature threshold – PiCoolFan supports both the Celsius and the Fahrenheit scales. The PiCoolFan kit contains all the hardware necessary for setting up the fan and the air distribution plate.

Comparing Wireless Standards 802.11ad & 802.11ah

Wireless LAN standards were first set up for serving the needs of laptops and PCs in homes and offices. These were IEEE 802.11a and b, and these later served to allow connectivity in different places such as in shopping malls, Internet cafes, hotels and airports. The main functionality of the standards was providing a wireless link to a wired broadband connection for email and Web browsing.

Initially, speed of the broadband being a limited factor, a relatively slow wireless connection was enough. Therefore, 802.11a offered up to 54Mb/s at 5GHz and 802.11b up to 11Mb/s at 2.4GHz, with both frequencies being in the unlicensed spectrum bands. To reduce interference from other equipment, both standards were heavily encoded using forms of spread-spectrum transmission. In 2003, a new standard 802.11g used the 2.4GHz band maintaining the maximum data rate of 54MB/s.

However, by this time, people started realizing the need for higher throughput, especially with increased data sharing amongst connected devices in the home or small office. By 2009, a new standard, 802.11n came up, which improved the single channel data rate to over 100Mb/s. The new standard also introduced spatial streaming or MIMO, multiple inputs, multiple outputs. The new modems had up to four separate transmit and receive antennas, carrying independent data that was aggregated in the modulation/demodulation process.

However, new WLAN usage models were continually raising the demand on throughput, such as projection to TV or projectors, streaming from camcorders to displays, video streaming around the house, airplane docking, public safety mesh and more. Catering to these VHT or very high throughput demands made it necessary to generate two new standards 802.11ac (an extension of 802.11n) and 802.11ad.

Standard 802.11ac runs in the 5GHz band, providing a minimum of 500Mb/s on a single link and 1Gb/s overall throughput. On the other hand, 802.11ad provides up to 6.7Gb/s using a spectrum of about 2GHz at 60GHz, but at short range. Operation at high frequencies limits the transmission range and obstacle penetrating capacity of the signals.

With the proliferation of local sensor networks working on low power, billions of IoT or Internet of Things and M2M or machine-to-machine device connections, a new standard is now deemed necessary. This new standard is the 802.11ah, working in the license-exempt 1GHz band and its final version is expected in 2016.

Standard 802.11ah is a down-clocked version of the 802.11ac standard. While adding some enhancements in the MAC and PHY layers, the new standard offers advantages such as power savings, multiple station support, better coverage and mobile reception.

For the standard 802.11ah, three main use-case categories are under consideration. These are Wi-Fi extended range networks, backhaul networks for sensors and meter data and sensor networks. The standard 802.11ah extends the transmission range with 1 and 2MHz mandatory modes, allows ultra-low power consumption, thereby offering multi-year battery life for large scale sensor networks and is optimized for long sleep times while handling small packet sizes.

Therefore, with 802.11ah, you can have several devices such as light sensors, temperature sensors and smart meters set up throughout the home, enabling your home devices and appliances to be considered smart.

Why is WAM Better than QAM?

Almost all wired and wireless applications today use the QAM or Quadrature Amplitude Modulation. These include the Fiber infrastructure, Wireless Backhaul, DSL modems, Cable modems, Cable TV, Satellite TV, Wi-Fi, Cellular and numerous other communication systems.

QAM systems use two AM or Amplitude-Modulated signals combined into a single channel – increasing the effective data rate while using the same amount of bandwidth. A QAM signal has two carriers, each with the same frequency, but differing in phase by 90 degrees. The term quadrature arises from the difference of one quarter of a cycle. If you call one of the amplitude-modulated signals the in-phase signal, the other becomes the quadrature signal.

Typically, the quadrature signal, multiplied with a sine wave, is subtracted from the in-phase signal multiplied with a cosine wave. The resulting signal is then amplified and transmitted over the air, wires or cables.

At the destination, a reversal of operations takes place by multiplying the in-phase output by a cosine wave and the quadrature output by a sine wave. Filtering them individually leaves only the lower frequencies. As these operations are entirely reversible, they ensure the preservation and exact recovery of the originally transmitted data.

Proliferation of communications devices and systems is putting considerable stress on bandwidth availability. For the past 40 years, QAM has completely dominated the advanced communication systems. Consequently, there are over seven billion connected devices using QAM technology.

Lately, a new Wave Amplitude Modulation or WAM technology is challenging this dominance of QAM. MagnaCom, who has patented and trademarked the WAM technology, claims the use of WAM can enhance nearly all wired and wireless applications. Additionally, WAM being backward compatible to legacy QAM systems, its use will not require any changes to the RF, radio or the antenna.

WAM technology uses a purely digital modulation scheme and is scalable. While using the same analog and RF circuits that QAM does, WAM needs no redesign and consumes only about one square millimeter space in modern semiconductor design. As the WAM technology is scalable, designers can now implement a smaller and lower cost solution.

Speaking technically, WAM represents a multi-dimensional signal construction technique working in the Euclidean domain. For the first time, designers can break the orthogonal signal construction. This provides an optimal handling of nonlinear distortion, increasing the system capacity. Overall, there is significant improvement over the legacy QAM systems.

The benefits of using WAM include a system gain advantage of over 10dB, while increasing the distance covered by over four times at half the power. This results in double the spectrum savings, offering better noise tolerance, major increase in speed and easier design at lower costs. Additionally, there is no need to replace any of the existing QAM equipment, as WAM is entirely backward compatible with QAM.

Compared to QAM, the new technology modulates information differently resulting in major system benefits. The use of spectral compression allows WAM to improve spectral efficiency by enabling an increase of the signaling rate. This allows reduction of complexity to a lower order. The use of nonlinear signal shaping by WAM offers inherent diversity of time and frequency domains, resulting in a lower cost and lower power design of the transmitter.

The Rezence Standard for Wireless Charging

Typical wireless charging technologies depend on magnetic induction to transfer power from a ‘mat’ to the specially designed mobile device under charge. However, Rezence holds forth the concept of spatial freedom, which extends the wireless power applications to go beyond the mat to any surface and into almost any mobile device. Unlike magnetic induction, Rezence works on the principles of magnetic resonance. With Rezence, the wireless charging ecosystem has a number of unique benefits.

The Rezence standard allows superior charging range. This amounts to a true drop and go charging experience, with charging taking place through almost any surface and through several objects such as clothing and books. The new standard is able to charge many devices simultaneously even when they have different power requirements – including Bluetooth handsets, laptops, tablets and smartphones.

The Rezence standard is an ideal choice for charging in situations involving kitchen appliances, retail and automotive applications. Rezence powered charging surfaces do not conflict with metallic objects such as coins and keys. Additionally, use of this new technology minimizes the hardware requirements of the manufacturer as it leverages the existing Bluetooth Smart v4.0 technology. Therefore, users can have Smart Charging Zones in the future.

The world already has multiple wireless power standards. Ultimately, the consumer will decide the most popular wireless power technology it will use. Presently, wireless power is undergoing the same process of certification and testing that other technologies such as 4G, 3G, Bluetooth and Wi-Fi have had to go through. Although technology selection and adoption is primarily a market-based mechanism, development of standards is a process separate and distinct from the former.

The Rezence standard is actually the released version 1.0 of the A4WP specifications, released in January 2013. Only when an outside standards organization accepts a specification, it is truly considered a standard. Therefore, organizations, including the A4WP, sometimes use the two terms interchangeably – as a matter of semantics.

Other organizations, including A4WP, are technically at the stage of development of the specifications. Additionally, A4WP is working actively with standard bodies around the world to ensure their technology will be adopted regionally as well.

Various organizations have promoted their wireless power technologies over several years. However, most of the older technologies have proven to be impractical in real-world applications. For example, they work well for single devices when these are positioned perfectly on a charging mat. Moreover, the charging range remains limited and the inability to handle differing power requirements at the same time makes this technology impractical.

When working with wireless power system design, heating and power absorption are dependent upon metal thickness and magnetic field strength. The older wireless inductive charging systems mostly use 115 KHz, at which frequency common household objects such as metal stickers, paper clips and even coins have higher power absorption and consequently, heat up. The Rezence system, with its operating frequency of 6.78 MHZ, does not cause similar heating up of common metal objects.

Therefore, unlike the older charging systems, in the Rezence method of charging, common metal objects do not heat up to create a hazard or trigger the termination of the charging process.

Get VGA from your Raspberry Pi

Those of you who use the single board computer, the Raspberry Pi or RBPi, know that it has two video outputs. It offers high definition video via the HDMI port and a composite video via the RCA port. For viewing the output of the RBPi on a VGA monitor, one must use an HDMI to VGA adapter or similar. However, there is a simpler and cheaper method now available – the Gert VGA 666.

The Gert VGA 666 is a breakout/add-on board, useful only for the RBPi Model B+. The board does not work on other RBPi Models such as A and B, as it requires the additional GPIO pins that are only available on the Model B+. Gert van Loo has designed this Gert VGA 666 board and has released it as an open source hardware design. Incidentally, Gert van Loo was associated with the initial design of the original RBPi and is one of the architects of the BCM2835 chip that forms the heart of the RBPi.

The Gert VGA 666 is a useful and neat solution for attaching a VGA monitor/screen to your RBPi. Additionally, this works out much cheaper than buying a converter or adapter for converting HDMI to VGA. A parallel interface from the GPIO pins drives the hardware natively for the VGA connection, using the same CPU load as the HDMI connection does. Users have the added advantage of setting up a dual screen, one for HDMI and the other for VGA. This is possible as the RBPi can drive both interfaces at the same time. With no CPU load, you can expect a VGA video display with resolution of 1080p60 or 640×480.

You can buy this adapter in the form of a kit, comprising the PCB for Gert VGA 666, a 40-pin header connector for the GPIO, a 15-pin female VGA connector, 20 through-hole resistors and two Pi supply stickers. When assembled and fitted on the RBPi, the board uses up nearly all the GPIO pins on the Model B+. Therefore, it will not be possible to use any other add-on boards at the same time when using the VGA adapter.

The decision to offer the adapter as a kit stems from the requirement of meeting EMC compatibility regulations. A fully assembled board would be required to meet most EMC regulations. However, these regulations do not cover the kit, as it is a homemade electronic product.

After soldering the board, plug it into the RBPi and power up the combination. However, the adapter does not work directly and you will need an intermediate solution for video output. You can use either an HDMI or a DVI-D monitor. If that is not available, use a composite monitor or TV via the RCA port. However, using the composite video means you will need to program the NOOBS on the RBPi.

After booting, you must install the necessary drivers for the Gert VGA 666 adapter. This requires an Internet connection, preferably via an Ethernet connection. If you simply plug in the Ethernet cable, Raspbian will automatically start to use it.