Monthly Archives: March 2017

Researchers Develop Thermoelectric Organic Transistors

Linkoping University scientists have made possible an organic transistor that is driven by temperature changes instead of by an electrical signal. Made of a thermoelectric material, the transistor brings about an appreciable current modulation for just a single degree rise or fall in temperature.

Professor Xavier Crispin, based at the Laboratory of Organic Electronics of the university, states that heat driven transistor is the first logic circuit to be developed that makes use of thermoelectricity.

Wide Range of Applications

The scientists foresee diverse uses for the new transistor. Since the device can record very small temperature changes, healthcare professionals can use it to fabricate therapeutic dressings that monitor the healing process along with treating the patient.

The scientists say it would be possible to build circuits that would respond to the heat contained in infrared radiations, too. This could be of particular use in developing heat cameras and similar devices.

The organic transistor is highly susceptible to minute heat changes. Compared to conventional thermoelectric devices, it is 100 times more sensitive to a drop or rise in temperature. This high level of heat sensitivity implies that just one electrical connector from a heat sensor electrolyte is adequate for sending a signal to the transistor. The researchers explain that a pair of a thermoelectric transistor and a sensor connector would be sufficient to make up a “smart pixel” for the camera.

A set of these smart pixels could make up a matrix, which may serve as a detector. This could be used in place of the numerous sensors used for detecting infrared rays in existing heat cameras. The researchers hope to add in more developments so that even a device as small as a mobile phone can include a heat camera. Since the materials needed for fabrication are non-toxic, inexpensive, and easily available, the feature could be had at a low cost.

Sunlight Charged Supercapacitor

The researchers built the heat-powered transistor by exploring a technique that allowed charging a supercapacitor by sunlight. The capacitor, developed a year ago, captures the light photons falling on it to convert to electricity, which is stored within it for further use. Crispin explains that it was crucial to establish the working of the heat driven supercapacitor before looking into possible electrolytes and the range of possibilities.

The university team researchers looked through a wide range of conducting polymers to turn out a liquid electrolyte that can produce a potential difference from a temperature gradient a hundred times more than that most electrolytes generate. While the positive ions of the electrolyte are small and move quickly through the liquid, the polymer molecules are negatively charged and massive, and move slowly. When a part of the electrolyte is heated, the lighter positive ions move to the colder regions rapidly. The separation of the positive ions from the negatively charged polymer molecules generates a potential difference or a voltage, which is adequate for transistor applications.

Team members Simone Fabiano, a lecturer, and Dan Zhao, a researcher engineer, have worked extensively with the electrolyte to show that heat signals can be used to make electronics controlled by heat signals.

How to Host XBee Sensors with the Raspberry Pi

Hosting sensors on the Raspberry Pi (RBPi) is so simple because the GPIO pins are all available. As most sensors need very little supporting components, hosting multiple sensors on your RBPi is possible. For instance, RBPi can simultaneously host multiple sensors for temperature, pressure, humidity, and other parameters for sampling atmospheric conditions from a weather station.

However, the RBPi does not support digitals signals on its GPIO pins. This is one reason the RBPi is so inexpensive. For accessing digital signals, the RBPi would need a digital to analog converter, preferably a 12-bit device with 4 channels.

Websites such as SparkFun and Adafruit carry a host of sensors and provide a huge amount of information about the products. Google also provides examples of using analog sensors with the RBPi. The restrictions of using only analog sensors and the 3.3 V maximum supply voltage makes the RBPi less versatile than its competitors such as the Arduino. In addition, on the RBPi you must run Python scripts as root, which makes it somewhat more difficult to do than doing so with the Arduino.

Other than connecting sensors directly to your RBPi, you can also consider using the RBPi as an aggregator node by using an XBee to connect to XBee-hosted sensors or Arduino-hosted sensors.

More specifically, you connect the remote sensor with the RBPi using XBee modules. For this, you will need to create a node first. Start with connecting the serial interface, which is a part of the GPIO header on the RBPi, to the serial interface on the XBee. Do not power on your RBPi or the sensor node, until after you have completed and verified all the hardware connections.

You will need an XBee breadboard adaptor and a breadboard. Plug in the adaptor on the breadboard. Now wire the 3.3 V and GND from the RBPi GPIO to the pins on your XBee adaptor. In case you are using the XBee Explorer Regulator from SparkFun, you may connect to the 5 V power line, as the XBee Explorer has an onboard regulator. The serial interface pins on the SparkFun board has the pins arranged in a header on the side of the board. This board also has the onboard regulator to protect the XBee, and you can connect the Explorer to the 5 V pin instead of the 3.3 V pin.

It is much easier to use connectors instead of wires. Therefore, consider soldering breadboard headers to the XBee adaptor and connect to the serial I/O header.

Next, connect the TXD pin of the GPIO on the RBPi to the DIN pin on the XBee Explorer. The RXD pin of the GPIO on the RBPi goes to the DOUT pin on the XBee Explorer. If using the SparkFun adapter, make sure you are connecting to the right pins—check the documentation for the same. Now take the coordinator XBee module and insert it into the XBee.

Before writing your own scripts, you need to download the special library from XBee. This provides a special Python module that encapsulates the XBee protocols and frame-handling mechanisms.

Metamaterial Cools Buildings without Using Energy

Engineers at the University of Colorado Boulder have built a metamaterial that can be used to cool structures without drawing on any energy. The material can also cool objects placed in direct sunlight without using water.

A metamaterial is an artificial substance with remarkable properties not possessed by natural substances.

According to Xiabo Yin, an assistant professor at Colorado Boulder and a director of the research, the new metamaterial could be a game changer in the field of radiative cooling technology. Since the technology does not make use of water and electricity, it presents a huge opportunity in the fields of power generation, agriculture, space research, and several other areas.

The metamaterial, which could make for an environmentally friendly and cost-effective technique for cooling homes and industrial applications, has been discussed in the journal Science. Thermoelectric power installations, which need a large amount of water for maintaining the low temperatures of the cold junction could instead make use of this material for cooling purposes. The hybrid material can be fabricated in the form of glass-polymer sheets in thickness of 50 micrometers. It is only marginally thicker than the kitchen aluminum foil and can be manufactured on rolls, making it economically viable for large-scale production.

When placed over an object, the film cools the surface beneath it by reflecting the incident solar energy radiations back. At the same time, the film helps the object lose the heat contained by emitting low frequency infrared radiations. Field demonstrations were conducted at Cave Creek in Arizona and Boulder in Colorado. The tests showed that at both places, the metamaterial had an average radiative cooling power of 110 W/square meters for 72 hours at a stretch. During direct sunlight at noon, the radiative power recorded was 90 W/square meters.

Gang Tan, an associate professor in the Department of Architectural and Civil Engineering of Wyoming University, explains the test results imply that about 20 square meters of the material installed on the roof of a single family home could achieve reasonably good cooling in summer.

Apart from cooling buildings and power plants, the new polymer-glass hybrid material can serve to enhance the efficiency and life of solar panels put up for electricity generation. Intense sunlight tends to damage solar panels. Yin explains that a layer of the material applied to a panel can boost the efficiency by almost 2%.

The cooling power of the material is approximately equal to the electricity produced by a solar panel of the same area. However, while solar cells can operate only during the hours of sunshine, the new material provides radiative cooling at all hours.

The researchers are now waiting for a patent for the new material and the technology. They are also working with the Technology Transfer Office at CU Boulder to look at prospective commercial applications. A potential project in the offing involves the creation of a model cooling-farm in Boulder sometime this year.

The team has been awarded a grant of $3 million for the invention of the metamaterial and the related research projects by the Advanced Research Projects Energy Agency connected with the DOE.

Name Badge with the Raspberry Pi

For people who interact a lot with others, it helps to build relationships if there is a small gizmo available as a handout. Apart from being a conversation starter, this could also be an advertiser for that upcoming project or story. Most people relish being handed a freebie, and a programmable one-off gadget is one of the best.

These were the exact thoughts running through Rob Reilly’s mind when he got a tiny color LCD for Christmas. He conceived the idea of a programmable name badge, as that would certainly grab eyeballs. Being configurable, the message could change to a logo, or graphics as necessary, maybe even through sensor inputs. When you have an idea to sell, having a self-made project considerably adds to your credibility. What Rob Reilly did with an Arduino Pro Mini, Josh King has accomplished with a Raspberry Pi (RBPi) Zero. He calls it the PiE-Ink Name Badge.

For the necessary parts of the name badge project Josh starts with the RBPi Zero, the PaPiRus 2-inch e-ink HAT, an Arduino Powerboost 1000c, and a Li-Po battery. He puts the parts together using some magnets and adhesive putty.

After soldering the header pins to the RBPi Zero, Josh attached the Powerboost, which is a useful power supply. It has a built-in load-sharing battery charger that allows the project to run even when the batteries are charging. Any 3.7 V Li-Po battery can power this DC-DC converter board, which transforms the battery output to 5.2 VDC for powering the RBPi.

At this point, Josh attaches the PaPiRus HAT to the RBPi Zero, securing all the boards with putty, ensuring a snug fit. A mini slide switch in series with the power supply wires completes the assembly and allows on-off functionality.

Josh has Raspbian already pre-installed on the SD card, so he follows it up with the setup for the PaPiRus. He needs to download all the libraries in place for the RBPi Zero to recognize the 2-inch screen. To fit into the e-ink screen, Josh had to scale all images down to 200×96 pixels.

The PaPiRus is an RBPi HAT compliant design with an interchangeable screen size—you can use a 1.44”, a 2.0”, or a 2.7” e-ink display. It has 32 Mb Flash memory with a battery backed RTC, and the onboard EEPROM allows it to be plug and play with the RBPi. To facilitate projects, there is an onboard thermal watchdog, a temperature sensor, and a GPIO breakout connector with solder pads. There are four optional slim line switches on the top, and an optional reset pin header to allow the HAT wake on alarm from the RTC. PaPiRus is suitable for powering from 3.3 or 5 V power supplies, and compatible with RBPi, Arduino, Beaglebones, and many more boards that are similar.

PaPiRus uses the ePaper technology, mimicking the appearance of ink on paper. This technology is different from LCDs, as it reflects light just as ordinary paper does. Moreover, similar to ordinary paper, the ePaper display can hold text and images indefinitely, even without battery power being present.

As the display does not require any power to retain the image, the entire electronics could go to sleep for days together before the image starts to fade slowly.

Metal Bellows in Engineering Applications

Metal bellows are versatile and a key enabling technology for a wide range of engineering applications. They play an essential role in controlling motion, vacuum, and pressure. Numerous industry sectors use metal bellows in a broad array of machine assemblies and components.

Being flexible, spring-like, and precision-engineered components, metal bellows are typically custom-designed, performing a variety of engineering functions. Metal bellows can convert temperature, mechanical, and pressure changes to linear or rotational motion. Flexible electronic applications can also use them.

Although the metal bellow is only a small part within the overall machine assembly, the role it plays is a critical one in the overall functionality of the system. While elegantly addressing a number of engineering challenges, a range of applications uses the bellow. These include—mechanical test stands, agriculture, solar power, semiconductor, ultra-high vacuum, cryogenic, military and defense, oil and gas service, aerospace, instrumentation, and industrial automation.

As part of the larger machine component or assembly, bellows generate a specifically defined dynamic response. In some cases, this provides a more precise, more reliable, and less expensive alternative to a more complex engineering solution.

Typical Applications

With advanced manufacturing techniques, designers can engineer metal bellows with precision and manufacture them with extremely small dimension. Several engineering applications benefit from using metal bellows and different engineering scenarios demonstrate their broad functionality.

Sensitive military and aerospace applications use the highly reliable metal bellows as mechanical backups for their mission-critical electronic systems.

Form and Function

A metal bellow has the physical form of a spring-like accordion, and is flexible and lightweight. Manufacturers fabricate bellows as a part of a leak-tight sealed assembly, having appropriate ends for allowing connections within the equipment. In both vacuum and pressure applications, the bellows appears as a ribbed or corrugated tubing.

The bellows can function like a spring for many engineering applications. However, when filled with a pressurized gas or liquid, or in conditions of vacuum, the bellows displays extreme sensitivity to various forces such as temperature and pressure changes affecting the hydraulic gas or fluid sealed within or outside the bellows. Knowing the coefficient of expansion of the gas or fluid, the designer can fashion the bellows to provide a dynamic and predictable mechanical response against these forces.

Mechanical Actuation

Sealed metal bellows, filled with a known silicone-based fluid, will extend or compress with temperature changes. This happens as the fluid inside experiences volume changes, in response to falling or rising temperature. The change in fluid volume translates into a linear movement of the bellows, producing a predictable response. Used within a machine assembly, the bellows provides precision positioning.

The advantage with thin-walled bellows is they remain flexible even under cryogenic conditions, suffering no compromise in their stroke. Since bellows retain their integrity and do not crack even at such low temperatures, they are very reliable for coupling, offset, rotation, extension, and compression capabilities. For instance, they are used reliably for pumping liquid nitrogen, liquid helium, and liquid oxygen in space valve applications.

The thermal expansion of the concealed fluid allows metal bellows to be used as indicators of temperature and pressure. Missile technology and navigation make use of metal bellows where low-temperature operations are critical. Astronomy applications use bellows for positioning mirrors precisely.