Monthly Archives: April 2018

Industrializing your Raspberry Pi

You can turn your Raspberry Pi (RBPi) into a completed computer system with the minimal effort. Using a pre-assembled, cost-effective kit will not only save you a lot of time, but also speed up the installation and slash development time as well, allowing you to realize the full potential of your single board computer. This industrialization of your SBC brings huge commercial potential and encompasses a wide range of applications, including using the system for payment terminals, communication systems, IoT products, home technology, medical devices, machine tool control systems, industrial automation, and more.

The PCAP 10.1-inch Touch Screen Kit from Inelco Hunter is specially designed to work with the popular single board computer, the RBPi. You can buy the kit in pre-assembled form and simply mount the RBPi onto the interface PCB on its rear, fixing it in place using the supplied pillars and screws. You can then mount the display as a panel or flush mount it to get resolutions up to WXGA.

Customers looking for a larger screen format for the RBPi can now upgrade from the earlier 7-inch display format from the same designer, Anelco Hunter. He developed this new screen for customers looking for extra screen space. Using the kit, customers can industrialize their equipment quickly and easily by providing it with a larger screen. No further upgradation is necessary, as the same programs and software already available for the 7-ich version will continue to be useful.

According to the Managing Director of Inelco Hunter, David Bushnell, the idea for a bigger screen format for the RBPi was born after a number of customer requests were made following the launch of their 7-inch kit. The kit maintains the same quality of the 7-inch model’s TFT screen with industrial grade while transitioning to the bigger screen format, maintaining the earlier high-quality metrics and ongoing availability.

A PCB provides the connections on-board for HDMI interface, along with the required conversions for signal, power, and backlight required by the TFT display. To drive the TFT display, the user has to supply it with 12 V at 2 A. This is apart from the 5 V at 2 A the RBPi requires for operating.

The PCAP touchscreen offers features such as pinch, zoom, and rotate through either USB or I2C connection. While the screen dimensions are 255 x 174 x 9 mm, the view area is 218 x 137 mm. The wide-angle IPS display offers a resolution of 1280 x 800 pixels.

Inelco Hunter has designed their display kit to work with all models of the RBPi family. They have tested the kit to operate at temperatures of +70°C and this underlines its reliability. This further supports the mean time before failure (MTBF) figure of 50,000+ hours. All these specifications make this display a good choice for those looking for a design with a long life and reliability.

Customers buying the kit will find a 10.1-inch Touch Screen TFT display, a pre-assembled interface PCB for HDMI to LVDS conversion, a connector for HDMI to HDMI interface, a micro USB to USB cable interface, and the pillars and screws for mounting the RBPi.

What are Digital Pressure Sensors?

Various industrial systems use pressurized air, water, and other fluids. They use sensors to regulate and maintain proper pressure at different points in their activities. Although many systems continue using analog pressure sensors, digital versions are fast replacing them. A few examples serve to illustrate why pressure sensors are important.

Industrial icemakers need water at minimum pressure between 20 and 40 psi at the inlet—this allows the water inlet valve to function properly—although the exact water pressure requirement is dependent on the particular make and model of the refrigerator.  Pressure sensors with media isolation (waterproofing) provide a quick method of determining whether the water pressure is adequate for making ice.

Corporate Average Fuel Economy (CAFE) regulations demand that by 2025, the average fuel economy should be 54.5 MPG fleet-wide. Although popular belief is, each car maker’s fleet should have a significant presence of electric and hybrid vehicles to meet CAFE requirements, manufacturers are working towards advanced diesel and gasoline engines that should be able to meet the standards by themselves. One model of such advanced engines is the Achates Power Opposed-Piston engine. It exhibits fuel economy gains of 30-50% with significant reduction of emission, and is more cost effective compared to other solutions. The Achates engine requires a fuel injection system capable of a 2000 bar injection pressure.

For cutting different types of very hard, heat-sensitive, or delicate materials, industrial machines often make use of a water-jet cutting system. This avoids heat damages to the workplace edges or surface. An ultra-high-pressure pump operating at 40,000-100,000 psi produces a high velocity, high-pressure stream of water at 30,000-90,000 psi. Special MEMS pressure sensors are necessary to achieve the desired accuracy, resolution, and repeatability in such high-pressure measurement systems.

All Sensors makes the DLVR Series of mini digital output pressure sensors based on their patented CoBeam2 TM Technology, providing overall long-term stability by reducing susceptibility to package stress. Compared to single die systems, the DVLR differential pressure sensor technology improves the position sensitivity.

The DC supply voltage option of 3.3 or 5 V eases the integration of the sensors into a wide range of measurement and process control systems. I2C or SPI interface options allow direct connection to serial communication channels. The sensor goes into very low-power modes between readings, thereby minimizing load to power supply for battery operated systems.

With a pressure range of 0.5 to 60 inH2O and a common mode pressure of 10 psig, the DLVR pressure sensors offer better than 0.5% accuracy over temperature. While the storage temperatures range from -40 to +125°C, the sensors can operate from -25 to +85°C, under non-condensing humidity limits between 0 and 95%. The sensors are available in ten types of device packages including E1NS, E1ND, E1NJ, E1BS, E1BD, E2NS, E2ND, E2NJ, E2BS, and E2BD.

The DLVR series of digital output sensors are compensated and calibrated by the manufacturer and provide a stable and accurate output over a wide range of temperature. Intended use for this series involves non-ionic and non-corrosive working fluids such as dry gases, air, and similar. Moisture or harsh media protection is also available in the form of an optional parylene protective coating.

Interfacing XBee Modules with the Raspberry Pi

You can use two XBee modules to exchange data between them, as they are modular, self-contained, and low-cost components using radio frequency to communicate. Most XBee modules transmit on the ling-range 900 MHz or on 2.4 GHz using their own network protocol.

The primary advantage of using XBee modules is their size—nearly as large as a postage stamp. Therefore, it becomes easy to use them as sensor nodes in small projects. They consume very low power, and incorporate a special sleep mode that reduces their power consumption considerably. This is of advantage when using them on battery or solar power.

XBee modules can read their data pins and transmit the collected data to another XBee module. Therefore, if you have a sensor node and a data-aggregator node, you can easily link them together with XBee modules. As there is no micro-controller on the XBee module, it has only a limited amount of processing power for controlling the module.

This limited processing power makes it suitable for several sensor nodes, but not for all. For instance, although the XBee module can read data from sensors, it cannot do so from sensors requiring algorithms to interpret or extrapolate meaningful data—the additional calculations this requires may need assistance from a microcontroller. Incidentally, configuring an XBee module with the Digi configuration tool, X-CTU, requires a computer running the Windows operating system. For other operating systems, use a virtual machine to run Windows.

The XBee line of wireless modules has a list of different types, and you must select the one most suitable for your project. Some modules support proprietary protocols from Digi, others support UART or SPI to 802.11 b/g/n (Wi-Fi), while others support the ZigBee, and 802.15.4 protocols.

Several popular XBee modules support the ZigBee protocol. Therefore, many projects use the ZigBee modules available in the market. ZigBee modules have several more choices based on application. For instance, there are ZigBee embedded surface mount modules, and others that support the ZigBee feature set, and 802.15.4 protocols. The most popular among these are modules supporting the ZigBee Pro feature set.

The advantage with ZigBee is it is an open standard based on the IEEE802 standard, useful for network communications. ZigBee supports the formation of mesh networks to configure and heal broken links automatically, and allows the use of intermediate probes to transmit data over long ranges.

You can use a ZigBee development module with on-board USB interface or use an FTDI cable to interface it. Usually, in a mesh topology, you will need to assign each node with their individual roles as coordinator, router, or end device. You will need at least one coordinator in the network, while the mesh will require several routers.

You can use the explorer dongle to plug in the ZigBee module, and use the USB connector on the dongle to plug the combination into one of the USB ports on the Raspberry Pi (RBPi). To communicate, you will need another pair of dongle and ZigBee module on the USB port of a computer or laptop. You will need to select the correct com port, and a common baud rate on a HyperTerminal to initiate communication between the modules.

What are Signal Generators?

While developing electronic systems, engineers test the device by stimulating it with different types of signals they expect it to encounter in the field. The piece of test equipment that engineers use for generating the various test signals is the signal generator. A signal generator may be used as a stand-alone development system or in combination with other test instruments.

Depending on the requirement, signal generators may come in various forms and types, with each of them providing different forms of signals. For instance, some output only RF signals, others audio signals, while some provide a train of pulses, and still others offer different shapes of wave-forms. Although different signal generators offer a variety of facilities and performance levels, they may be broadly classified as:

Function Generators

This type of signal generators typically generates simple repetitive waveforms such as sine, sawtooth, square, and triangular waveforms. Early models of signal generators used analog circuits to generate the waveforms, but later models depend on digital circuitry to produce them. Users can set the frequency for the waveforms from the front panel of the instrument. Function generators operating at high frequencies are more expensive.

Arbitrary Waveform Generators

These signal generators can produce arbitrary waveforms that the user specifies. They are one of the most complex function generators and therefore expensive. Users can demand almost any shape of waveform for the instrument to generate, sometimes even by specifying points on the waveform. Some manufacturers compromise on the bandwidth because of the techniques they use to generate the signals.

RF Signal Generators

As the name suggests, these signal generators output radio frequency signals. Earlier analog models used free running oscillators with frequency locked loop techniques for improved stability. Nowadays, manufacturers use frequency synthesizers for achieving the stability and accuracy. Some also use direct digital synthesis along with phase locked loops for generating the required RF output.

Vector Signal Generators

These are a special type of RF signal generators for generating complex modulation formats such as QAM, QPSK, and similar.

Audio Signal Generators

These produce signals within the human audio range, typically from 20 Hz to 20 kHz. Suitable for audio and frequency response measurements, some versions offer repetitive and non-repetitive linear and logarithmic sweeps across the entire output. Some audio signal generators can synchronize with an oscilloscope to enable a visual display of the frequency response of the device under test. Usually with very flat response and extremely low levels of harmonic distortion, audio signal generators help in the measurement of distortion from the device under test.

Pulse Generators

This type of signal generators output pulses with variable height, width, and rise/fall times. Users can program them to output a single pulse after a defined time delay. The user may program all aspects of the pulse—its height, width, DC level, and its rise and fall times.

The large variety of signal generators producing different types of waveforms allows engineers to use them in various applications. They are useful for testing RF equipment, logic boards, and in hosts of other areas. Of course, for achieving the proper objective, the engineer has to determine the type of signal generator necessary for a given job.

What are USB Controlled Synthesizers?

Almost all devices now use the popular Universal Serial Bus (USB) interface for connecting and transferring data to and from other devices. Even laboratory devices are now available with the USB as their main interface to computers. Now, users can control frequency synthesizers also through the USB interface. Although neither the performance nor the features they offer are anywhere near those that bench top instruments provide, USB controlled synthesizers have their advantages. USB controlled synthesizers, although providing basic functions only, are far cheaper, requiring only a computer and software to operate. They are easy to handle, being mostly plug-and-play, have a tiny footprint, and yet, some of them operate beyond 25 GHz, with ultra-low phase noise. Here is a review of some of the popular synthesizers.

Pasternak Synthesizers

The synthesizer family, PE11S390X from Pasternak Enterprises, is USB-2.0 controlled. These lab or desktop type instruments collectively cover a frequency range of 25 MHz to 27 GHz, and are useful in combination with other instruments for testing equipment during their design and development phases. As they are extremely compact, engineers can use them virtually anywhere, even while testing and conducting measurements in the field.

The accompanying USB cable supplies control and power to the synthesizer from a laptop, which also doubles as the measurement interface. The synthesizer connects to the device under test through an accompanying coaxial cable with a male MMCX connector on one end and a female SMA connector on the other.

The PE11S390X family consists of six models, with the low end in the group covering 35 MHz to 4.4 GHz, and the high end covering the range of 24 to 27 GHz. At an offset of 100 kHz, the various models have a phase noise ranging from -75 dBc/Hz at 27 GHz to -103 dBc/Hz at 4.4 GHz. Users can adjust the output power from -20 to +18 dBm, in steps of 1dB.

Although the synthesizers operate from an internal clock of 50 MHz, users can operate them from an external reference between 10-70MHz. Other features available are synchronization to other test instruments, with LEDs indicating the USB connection, PLL lock, and RF power output. Users have the choice of controlling the synthesizers through Windows, Mac, or Linux platforms, and each has its own non-volatile memory for storing the last setup. All units operate from 0°C to +55°C.

Fairview Synthesizers

The USB controlled, phase locked loop (PLL) frequency synthesizer family from Fairview Microwave Inc. offer high levels of signal integrity, superior frequency stability and accuracy, and exceptional phase noise characteristics. Fairway family of synthesizers is useful or applications involving bench top test and measurements of microwave radios, signal generators, and equipment involved with electronic warfare.

With the GUI command control and DC power coming through USB-2.0 connectors from a PC or laptop, these rugged and compact synthesizers cover a broad range of frequency bands from 25 MHz to 27 GHz. Users can control the power output up to +19 dBm and adjust it down by 50 dB in 1 dB steps. With phase locked loop speeds of 1ms, the synthesizers offer phase noise as low as -108 dBc/Hz at an offset of 100 MHz.