How Long Does it take for a Circuit Breaker to Operate?

Electrical power systems all over the world use circuit breakers as important and critical components. As they play a key role, engineers periodically test circuit breakers. One of the most important test methods is the timing test, which measures the mechanical operating time of the breaker’s contacts. A timing test averts damage to a circuit breaker, as the incorrect operation of a circuit breaker prevents fatal consequences on connected equipment and substation personnel.

Various measuring devices have evolved for measuring the operation times of a breaker. For instance, although are no longer in use, first-generation devices used the oscillographic mode of recording curves. The present methods of testing, the second generation, are based on digital timers converting pulses to time. The latest concept for testing circuit breakers is through the analysis of signals from mechanical vibration.

Circuit Breaker Operation Times

The technically operational quality of a three-phase circuit breaker is an important parameter of its operation times—characterizing the process of opening and closing of its contacts. The international standards of the International Electrotechnical Commission, the IEC 56.3.105, define these time parameters. The standard quantitatively describes the switching on and off times of the process as:

Time discrepancy between contacts — the diverging interval characterizing the disconnection or connection of the breaker contacts during non-simultaneous switching.

Closing time — the interval from the time of energizing the closing circuit (the circuit breaker being in the open position), to the moment the contacts strike the poles.

Opening time of the breaker — the interval from the time of energizing the opening release (the circuit breaker being in the closed position), to the moment the contacts separate at all the poles.

Worth noting is the time discrepancy between the contacts of the breaker. This should be within specified tolerance limits—usually 5 ms. This is important, as the time difference in closing or opening of all contacts may cause huge voltage spikes with a potential to damage the network and its equipment.

Digital Timer Meter

Digital timer meters are typically built with interconnected functional blocks such as input circuits, the micro-controller, a display, and a keyboard. The micro-controller is the central unit of the meter, while the input circuit eliminates disturbances and protects the unit.

The input circuit usually includes a converter with an output voltage of about 50 V. An opto-isolator ensures the optical isolation between the parts of the device directly connected to the breaker under test, and the other circuits of the meter. This protects components and digital circuits to ensure standardization of the signal for further digital processing.

Principle of Operation

The measuring process employs a principle known as the time-pulse method. This allows counting of pulses of a regular frequency in time intervals. The software in the micro-controller allows counting the pulses initiated by an external signal obtained from the breaker’s drive system.

A signal corresponding to the opening or closing of each contact of the breaker closes the time gates. As soon as the signals for the contact closure appear, the micro-controller copies the contents of the counter into its memory. The number of pulses the micro-controller counts is proportional to the interval elapsed from the moment of triggering to the moment of closing.

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.

How Does Ladder Logic Work?

Over the last 30 years, there has been a significant evolvement of ladder logic for industrial controllers. It now supports advanced functionality that includes data acquisition, networking, data manipulation, motion control, and process control. Designers starting a new control system are faced with many basic functions this tried-and-trusted language needs to perform, and it does so, almost effortlessly.

Object Detection

Detecting the presence of an object is one of the most pervasive functions a control system is asked to perform. Whether it involves detecting an object passing by on a conveyor, the closing of a gate, or locating a machine part as it revolves, object detection is a staple function in the automation industry. Objects can be sensed in myriad ways, and these include mechanical, inductive, capacitive, optical, and ultrasonic techniques and devices to detect proximity or nearness.

Limit Switches

The limit switch is a most basic sensor, mostly an electromechanical device detecting the absence or the presence of an object. As the actuator of the switch touches the sensed object, it operates a set of contacts. Depending on the actuator style, the specific means of contact may vary from plungers to wands, springs, levers, and rollers. However, the moving parts are prone to damage and wear, and it may not always be possible or desirable to make physical contact with the object to be sensed.

Inductive Proximity Switches

Non-contact sensing technology uses inductive proximity switches to detect the absence or presence of metallic objects without actually making contact with it. These are the most common and inexpensive devices. Inside the proximity switch is an oscillator driven coil. The magnetic field created by the oscillator appears at the active face of the switch. As soon as a metal target approaches this area, the electromagnetic field reduces, and this turns the switch on or off.

Capacitive Sensors

For objects that have a dielectric constant different from air, detecting them is easy with a capacitive sensor. Unlike the inductive proximity sensors that sense only metal objects, capacitive sensors can detect plastic, liquids, and wood. Although their method of operation is similar to that of the inductive proximity sensors, capacitive sensors detect objects based on an electrostatic field rather than an electromagnetic field.

Ultrasonic Proximity Sensors

These sensors measure the time of flight of a burst of sound impulse from the source until detecting the echo signal returned by a reflection from the detected object. Almost all materials reflect ultrasonic sound, which remains unaffected by color, transparency, or polish of the object.

Photoelectric Sensor

These sensors use a light beam as the detecting medium. Most popular photoelectric sensors are the diffuse, reflective, and through-beam types. The sensing distance depends on the type of light used—laser, LED, infrared, or visible.

Diffuse Sensors

Diffuse sensors contain both the receiver and emitter in the same unit. The optical beams may be either slightly diverging, or parallel. When an object appears in the luminous beam, it causes diffused reflection. The receiver detects the reflections from the object.

The ladder logic represents the contacts of the sensor and the PLC CPU assigns it a memory location. The CPU represents them in the Normally Open or Normally Closed in the ladder logic.

A Raspberry Pi Computer in an Altoids Tin

Turning an Altoids Tin into a Raspberry Pi computer

Turning an Altoids Tin into a Raspberry Pi computer

Although Altoids, a brand of breath mints, has its origin in the UK, it is less widely available there than it is in the US. The mints come packaged within a distinctive tin case, which people commonly reuse for different purposes, mainly as a container for small household items such as sewing materials, coins, paper clips, among many other items.

DIY enthusiasts often find the tins eminently suitable to contain electronic projects. For instance, Texas Instruments makes the BeagleBones, a single board computer, with rounded corners deliberately shaped in, so it will fit within the tin box. You can easily use the Altoids tin for enclosing the CMoy pocket headphone amplifier. The design of some microcomputer kits allow them to fit perfectly in the Altoids tins.

All the above led M. Wagner to come up with an idea of housing a Raspberry Pi (RBPi) SBC within an Altoids tin box. With the release of the RBPi Zero, he firmed up the project, calling it the PiMiniMint. His first version of the PiMiniMint had a screen, Wi-Fi, Bluetooth, 32 GB storage, infrared camera, and a full-size USB port. However, he found no space for a battery—to add the battery, he needed to remove the camera. His latest version of the PiMiniMint has a battery that lasts about 6-8 hours, a 2-inch screen, 32 GB storage, Bluetooth, Wi-Fi, and an OTG cable serving as a full-sized USB port.

Wagner uses a 1200 mAh 3.7 V Li-Po battery for PiMiniMint. This thin, rechargeable battery fits easily under the RBPi inside the case. He has soldered the red and black wires from the battery to the ‘+’ and ‘—’ connection points on the charging circuit. Any 3.7 V Li-Po battery should work here, preferably thin ones that the tin can hold.

Although the RBPi runs at 5 V, the battery needs 3.7 V to charge. Li-Po batteries are notorious for exploding if overcharged for long or for not being charged properly. Adafruit has a circuit that both charges the Li-Po and steps up its voltage to 5 V for the RBPi. However, Wagner uses a cheaper option—a generic USB charger. He chose a USB charger with a 3.7 V battery and with an output of 5 V. Although these tiny chargers do require a bit of preparation and de-soldering to get them to work with the RBPi, they are much cheaper.

To fit into the Altoids tin case, Wagner chose to use the RBPi Zero. Usually, the RBPi models do not boot off a hard disk, but needs an SD card. Wagner used one that had a suitable OS on it. You can select the OS of your choice and load it into an SD card. As the RBPi Zero does not come with any header, it is necessary to solder a 2×40 male header on the RBPi to connect to the iotHAT.

The Redbear iotHAT is a little HAT for the RBPi Zero, sitting directly on top and interfacing with the RBPi. The HAT gives the RBPi Zero capabilities such as Bluetooth and Wi-Fi. Wagner chose the 2-inch Adafruit NTSC/PAL screen simply because it fits the tin case.

PiFM: A Pirate Radio with the Raspberry Pi

The popular single board computer, the Raspberry Pi (RBPi), can work as a radio transmitter as well. Using a simple hack, you can turn your RBPi into a powerful FM transmitter with adequate range to cover a bike parade, high school ball game, silent disco, DIY drive-in movie, or even your entire home. However, the broadcast frequency covered by the RBPi is rather large—one to 250 MHz, and there is a possibility this will interfere with government bands. Therefore, it is advisable to limit the transmissions to the standard FM band of 87.5 to 107.9 MHz.

You do not need much to make the RBPi start transmitting. The RBPi board itself, a power source, and the SD card with the OS is all that is necessary. The only accessory required is a piece of wire, which acts as the antenna. The entire project runs on the software PiFM.

Oscar Weigl and Oliver Matios developed PiFM originally, and Ryan Grassel revised it. This project uses the PirateRadio.py script, which enables playback without accessing the command line, while handling most common music file formats automatically. Wynter Woods, a MAKE labs engineering intern, wrote the script.

Oscar and Oliver had hacked the original PiFM code over a few hours. To output FM radio energy, their code used the hardware on the RBPi that actually generates spread-spectrum clock signals on the GPIO pins. Therefore, to turn the RBPi into a really powerful FM transmitter, all that was necessary was to add a wire length acting like an antenna to one of the GPIO pins. The original code used the GPIO pin 4 with a wire of length about 20 cm attached to it. For transmission, Oscar and Oliver had chosen the frequency of 100.0 MHz.

When Sam Freeman and Wynter Woods tested the present project, they found the FM signal only deteriorated once it had to pass through several conference rooms with heavy walls. The signal was able to cover 50 m easily, and objects such as heavy metal cabinets could stop it. They found the sound quality acceptable, although it has some clicks that came from the CPU switching to tasks other than playing music. For the technically minded, a kernel mode driver uses the DMA controller for preventing the RBPi CPU from being loaded, and thereby plays smooth music.

The Python script calls a C program that maps the peripheral bus of the physical memory into virtual address space. After this, it enables the clock generator module and sets points its output to GPIO4. Note that you will not be able to use any other GPIO pin at this time. It also sets the frequency of transmission to 100.0 MHz, which acts as the carrier. If you receive this on a radio, the radio will stop the background noise and become silent.

The carrier is modulated by the audio produced by adjusting the frequency using the fractional divider between 100.025 and 99.075 MHz. The fractional divider can produce audio with only 6-bit resolution. As the RBPi is very fast, it can use 128 subsamples on every real audio sample to produce 9.5-bit audio. The subsample algorithm now gives full 16-bit quality sound with FM pre-emphasis.

Colorful Images from Electron Microscopy

Almost everyone treats Christmas as the time to get away from regular work. Surprisingly, there are exceptions, such as Roger Tsien. This late biochemist would do an extra two weeks of uninterrupted research in his lab during Christmas. In one of his sojourns, he gifted the world the first electron micrographs—in color. His method used to create them will dramatically advance cell imaging.

Scientists use Electron Microscopy (EM) for magnifying objects up to 10 million times their original size. The technique makes use of accelerated electrons for the purpose. Conventional EM images are in gray scale, and scientists add color using computer graphics programs, once the images are recorded. Tsien and his colleagues modified the EM technique for directly incorporating color labeling into the images.

Along with co-workers Mark H. Ellisman and Stephen Adams, Tsien devised techniques for employing serial applications of various lanthanides or rare earth metals, which served as the labels. Along with this, the researchers used the EELS or electron energy-loss spectroscopy type of Ems. EELS is capable of differentiating among the lanthanides. It does this by measuring the differences in energy deflected or absorbed by each lanthanide from an electron beam.

For instance, for creating the color image of a cell organelle such as an endosome, the researchers had to stain the sample initially with a lanthanide called cerium. This made the sample appear green when viewed under EELS. After removing the excess cerium, they applied the element praseodymium. This targeted another protein within the sample, which EELS now registered as red. Now all that the scientists had to do was to overlay the green and red images onto a traditional gray scale EM image and create the composite image. The final image highlighted different distinct regions of the endosome with red and green color.

In the November issue of the publication Cell Chemical Biology, Tsien, along with his coauthors, has described their multicolor EM technique. Although the technique is still very new, scientists are using it to obtain new information about cell structure. For instance, regular light microscopy is incapable of showing protein movements with and between cells. With the new technique, scientists can now view cell components at a much higher level of detail.

For instance, until now, scientists had only a hypothesis about the fate of certain molecules since they are too small to be visible using light microscopes. EELS offered vibrant proof and confirmed the hypothesis. So far, scientists had only conjectured that certain CPPs or cell penetrating peptides were responsible for ferrying molecules as cargo into cells, and that the cells then took up these molecules into the interior of endosomes. With the praseodymium coloring one kind of CPP with a red label, scientists were able to verify their hypothesis, as the CPP visibly ended up inside the endosome. At the same time, another molecule, colored vivid green with cerium, ended up predictably at the endosomal surface.

Tsien’s death has deprived the world of further contributions to this transformative technique. However, the innovations will continue to inspire his co-workers and the newer generation of scientists. Tsien, as a fitting last gift to the scientific world, added color to electron microscopy to allow them to see more within cells.