Tag Archives: infrared

Connect with a New Type of Li-Fi

Many of us are stuck with slow Wi-Fi, and eagerly waiting for light-based communications to be commercialized, as Li-Fi promises to be more than 100 times faster than the Wi-Fi connections we use today.

As advertised so far, most Li-Fi systems depend on the LED bulb to transmit data using visible light. However, this implies limitations on the technology being applied to systems working outside the lab. Therefore, researchers are now using a different type of Li-Fi using infrared light instead. In early testing, this new technology has already crossed speeds of 40 gigabits per second.

According to the Li-Fi technology, a communication system first invented in 2011, data is transmitted via high-speed flickering of the LED light. The flickering is fast enough to be imperceptible to the human eye. Although lab-based speeds of Li-Fi have reached 224 gbps, real-world testing reached only 1 gbps. As this is still higher than the Wi-Fi speeds achievable today, people were excited about getting Li-Fi in their homes and offices—after all, you need only an LED bulb. However, there are certain limitations with this scheme.

LED based Li-Fi presumes the bulb is always turned on for the technology to work—it will not work in the dark. Therefore, you cannot browse while in bed in the dark. Moreover, as in regular Wi-Fi, there is only one LED bulb to distribute the signal to different devices, implying the system will slow down as more devices connect to the LED bulb.

Joanne Oh, a PhD student from the Eindhoven University of Technology in the Netherlands, wants to fix these issues with the Li-Fi concept. The researcher proposes to use infrared light instead of the visible light from an LED bulb.

Using infrared light for communication is not new, but has not been very popular or commercialized because of the need for energy-intensive movable mirrors required to beam the infrared light. On the other hand, Oh proposes a simple passive antenna that uses no moving parts to send and receive data.
Rob Lefebvre, from Engadget, explains the new concept as requiring very little power, since there are no moving parts. According to Rob, the new concept may not be only marginally speedier than the current Wi-Fi setups, while providing interference-free connections, as envisaged.

For instance, experiments using the system in the Eindhoven University have already reached download speeds of over 42 gbps over distances of 2.5 meters. Compare this with the average connection speed most people see from their Wi-Fi, approximately 17.5 mbps, and the maximum the best Wi-Fi systems can deliver, around 300 mbps. These figures are around 2000 times and 100 times slower respectively.

The new Li-Fi system feeds rays of infrared light through an optical fiber to several light antennae mounted on the ceiling, which beam the wireless data downwards through gratings. This radiates the light rays in different direction depending on their wavelengths and angles. Therefore, no power or maintenance is necessary.

As each device connecting to the system gets its own ray of light to transfer data at a slightly different wavelength, the connection does not slow down, no matter how many computers or smartphones are connected to it simultaneously.

Phosphorene Challenges Graphene as a Semiconductor

Though silicon has been the basis of semi-conductors for decades, it is facing stiff competition from other materials that promise to deliver several extras to consumers who like to enjoy more flexibility with their gadgets.

For some time, graphene, a one atom thick allotrope of carbon has been under consideration for use in electronic devices because its thin structure allows electrons to travel across it much more rapidly than they would do across silicon. However, graphene has severe limitations, as its conductivity is a little too high to be of much use in electronic devices, which need semi-conductors or materials with medium levels of conductivity. Another newly developed material dubbed phosphorene, which can form identical thin layers and is a semiconductor as well, offers a wider scope in electronics.

Phosphorene particulars

Scientists at the Technical University of Munich (TUM) have prepared a semiconducting material with black phosphorus in which a few phosphorus atoms have been swapped by arsenic atoms. Replacement of the phosphorus atoms with arsenic has caused the band gap to reduce to 0.15eV, which makes the material an effective semiconductor.

Phosphorene or black arsenic phosphorus can form very thin layers like graphene. Unlike silicon, which is hard and brittle, phosphorene is easy to manipulate into different kinds of structures and shapes. This makes possible a great range of electronic devices with considerable mechanical flexibility.

Scientists at TUM have built on technology that allows the fabrication of phosphorene with the application of high pressure. This reduces the production costs considerably. The research workers have been able to fine-tune the band gap exactly according to specific requirements by tweaking the arsenic concentration. According to Tom Nilges, who is heading the research team at TUM this has enabled them to produce a wide range of materials with diverse electronic properties that were not possible earlier.

Field Effect Transistors

American scientists from Yale University and the University of Southern California (USC) have collaborated with the researchers at TUM to build devices like field effect transistors with phosphorene. A group headed by Dr. Liu and Professor Zhou of the Electrical Engineering Department at USC has studied the transistor characteristics.

Infrared Detectors

Further exploration of the material by the scientists revealed that the material when heavily doped with arsenic could be used for infrared detection. For instance, when the arsenic concentration is as high as 83%, the band gap in phosphorene is about 0.15eV. This fact makes it an effective sensor for infrared rays of long wavelengths. Researchers expect that the new substance can be effectively used as Light Detection and Ranging (LIDAR) sensors, which find use in applications for tracing dust particles and pollutants in the atmosphere and as distance sensors in vehicles.

Anisotropic behavior

Another noteworthy feature of phosphorene is its anisotropic nature. Electronic and optical properties of the material were studied using ultra-thin films in two mutually perpendicular, x- and y-axes. It was observed that the properties were different in the two directions.

Phophorene has an edge over other newly discovered thin-layered semiconductors because it is very easy to peel off layers from a parent black phosphorus crystal.

How do motion detectors work?

Whether it is really a cat or a cat burglar trying to sneak into your house at night, a motion detector is a more prudent device to have around, rather than trying your luck with a baseball bat. The trick is in knowing what type of motion detector to use at what point, since there are so many varieties of them and that could be confusing. It helps to know how some of the more common types of motion detectors work.

Typically, there are two types of motion detectors – passive type and active type. The differentiation depends on whether a detector is injecting energy into the environment for detecting a change. Active types inject energy into their immediate environment, whereas, passive types do not. Both devices are simple electronic components.

Active type motion detectors can use light, microwaves or sound for detecting movement. The most common type of active motion detector is a beam of light crossing the door with a photo sensor on the other end. As soon as a person breaks the beam of light, the photo sensor detects the change for light reaching it and either rings a bell or flashes a light.

Many places have automatic door openers. These can detect when someone passes near and opens the door in response. A device above the door sends out bursts of microwave radio energy at periodic intervals. A sensor waits for detecting reflected energy. When a person moves into the range of the microwave energy bursts, the amount of reflected energy changes or the time taken for the reflections to arrive changes and the box triggers an arrangement that opens the door.

Pyroelectric sensors or Passive Infrared detectors can sense the heat given off by a human. To make the sensor sensitive to the temperature of a human body, the sensor must be capable of sensing skin temperatures of around 93°F or 37°C. Such sensors are typically sensitive to the infrared energy wavelengths of the range 8-12micrometers, since the human body radiates wavelengths between 9 and 10 micrometers.

To prevent the sensors triggering false alarms for example, a sidewalk cooling off at night, a pyroelectric type motion detector detects only rapid changes in its field of view. That makes these sensors insensitive to a person standing still. However, the amount of infrared energy changes rapidly when a person is moving or walking by, enabling the sensor to detect it easily.

Since infrared energy is a form of light, a plastic lens can very easily bend or focus it. That is how these sensors have a wide field of view. Most detectors have one or sometimes two sensors within them looking for changes in infrared energy. However, infrared sensors installed within a room are not very capable of detecting snoopers or peeping toms trying to peek in through a window. That is because a motion detector sensitive to infrared energy is unable to detect it through glass windows.

If you have a four-legged friend in your home, you have to get sensors that are pet immune, to make sure the friend is not mistaken for an intruder.

Automate Your Home HVAC System from the Internet Using the Raspberry Pi

The HVAC devices in your home, typically the air-conditioner, thermostats, heating and ventilation, use one or more remote handheld devices working on Infrared (IR) technology. As the HVAC devices are from different manufacturers, you will most likely own a multitude of remote devices, making it difficult to handle and set each of them independently.

However, with the Raspberry Pi or RBPi, a small board called the IR Remote Shield and a wireless interface, you can control all the HVAC devices and that too from the Internet. Imagine setting up the environment in your home just as you are leaving office, so that you have a cozy atmosphere to relax at home.

There are two steps in this project. The first step involves teaching the Raspberry Pi and IR Remote Shield combination the codes that the remote handheld devices utilize to control the various functions of each of the HVAC devices. The second step is to connect the RBPi to the Internet through any one of the wireless interfaces such as Wi-Fi, 3G, GPRS, Bluetooth, and ZigBee or 802.15.4. These interfaces are available from Cooking Hacks, and you can choose one.

After you connect your RBPi to the Internet and feed in the IR codes used by your HVAC components, you can use a webserver, a laptop or even your Smartphone to control all your home HVAC appliances from anywhere in the world. But, a few words about Infrared technology first.

Started in 1993, IrDA or Infrared Data Association is the technology popularly used for controlling devices such as air-conditioners, TVs, radios, audio systems and many others. It is based on light rays in the infrared spectrum and invisible to the human eye. Using infrared transmitters and receivers, communication between two devices can be established in direct line of vision. The infra-red transmitters use special types of Light Emitting Diodes and the receiver uses a photocell sensitive only to the infra-red light.

Infra-red communication or control uses serial data transfer by emitting pulses of light, which is coded in binary, a language micro-processors are capable of deciphering. Therefore, for deciphering the binary code protocol that the remote is sending, you must hold the remote in front of the receiver on the IR Remote Shield mounted on your Raspberry Pi.

To decode and copy an IR code, press the “Receive” button on the IR Remote Shield. This will allow RBPi to capture the code the remote button is sending. In the software, you will have to tag each code with its individual function, for example, a certain code may be for raising the temperature and another for lowering it.

Once all codes from all the remotes are in the RBPi, it is a simple matter to map the codes and their functions on a web application. As the RBPi is connected to the Internet, any browser on the Internet can call up the web application, and the specific settings for the HVAC units altered. This allows the software program running on the RBPi to send the altered binary code to the specific HVAC unit via its IR link and change its status.

What is Infrared?

What is Infrared?

The electromagnetic spectrum has waves of various wavelengths. Human eyes are capable to seeing the light that form a small part of electro magnetic spectrum. The waves with shorter wavelength as well are longer wavelengths than the visible spectrum are not visible. Infrared are waves that have longer wavelengths than the visible spectrum. The wavelengths corresponding to the Infrared waves are in between 750nm to 1mm.

Infrared waves cannot be seen but can be felt in the form of heat. Since the main source of infrared emissions is thermal source, so any thing that has temperature will emit Infrared emissions. Most of them are not noticed because they are not so strong. Higher is the temperature of the object, greater will be the Infrared emissions. Substances that seem cold such as a cube of ice also emit infrared.

Uses of Infrared:

  • Night vision: Infrared filters are utilized to filter 99 percent of the light of the visible spectrum and allow maximum infrared light to pass through them. This helps in viewing objects even in the dark based on their infrared emissions.
  • Thermo vision: Infrared emissions are utilized to find out the temperatures of distant objects. All celestial bodies emit strong Infrared emissions. These emissions are an easy way to study about the topography as well as climate of the celestial bodies.
  • Communication: Infrared transmission is an easy way to transfer data for a short distance. Infrared finds its application in remote controls in which the Infrared LEDs are utilized to emit radiations that are focused over the Infrared acceptors. The Infrared LEDs also find their application in movement sensors such as optical mouse used in our desktop.


  • Spectroscopy: Infrared waves find their applications in analysis of the molecules.
  • Satellite images: Infrared imaging is utilized by satellites to send in the details regarding the weather and geography of a place.