Category Archives: Guides

Solid State Drives – Why Are They So Fast?

For most people, an HDD or hard disk drive inside their computer is the flat broad box that stores their Operating System, files, documents, and other essentials. So far, not many users were aware of the inner workings of their HDD. Lately, with speeds of computers going up many folds, people have started looking at alternatives for the HDD – the SSD or the Solid State Drive.

Whatever else you change in your computer system, the general experience remains the same. For example, you may get a new display, add more RAM or install a new graphics card. Barring a few moments of exhilaration, you do not experience the constant euphoria that you get when you replace your regular HDD with an SSD.

An SSD suddenly transforms your computer into a high-speed demon. Additionally, you get this feeling every time you use the computer. Even if you do not realize this increase in speed with an SSD, you will appreciate it as soon as you have to revert to operating a computer with a regular HDD. It is truly amazing the way this new technology is helping to transform our computer experience.

To understand the functioning of SSDs, it is necessary to know the computer’s inner structure or architecture regarding its memory. A computer’s memory architecture is actually made up of three sections: the cache, the temporary memory and the actual memory storage itself.

The CPU or the Central Processing Unit of a computer is intimately connected to the cache memory and accesses it almost instantaneously. As the computer operates, the CPU uses the cache memory as a sort of scratch pad for all its interim calculations and procedures.

The temporary memory, also known as the RAM or Random Access Memory of a computer is the place where the CPU stores information related to all the active programs and running processes. Although the CPU can access the RAM at high speeds, the access is slower than that for cache memory.

For permanent storage, your computer uses the memory within the HDD or the SSD. These may be programs, documents, configuration files, movie files, songs, and many more. Unlike cache and RAM, an HDD or an SSD retains its contents even when the computer has been shut down.

When people replace their HDD with an SSD, their computer operates at a higher speed even when they have not updated their cache or RAM. This is fundamentally because of the difference in the way of working of an HDD and an SSD.

An HDD is essentially an electromagnetic device. Inside, there is a motor to spin the several magnetic platters stacked one on top of the other. Before the CPU can read data from the magnetic plates, they have to spin until the right sector comes under the reading heads, which then move in to read from the exact location. All this mechanical movement takes time.

On the other hand, the SSD, being an all-electronic device, involves no mechanical movements. It uses a grid of electrical cells to store and retrieve data. Moreover, these cells are further separated into sections called pages. Further, pages are clumped together to form blocks. All this contributes to the fantastic speed of an SSD.

Detecting Plunger Movement in DC solenoids

DC solenoids are used in many applications that require movement of a part to be arrested in some way, to be released when an event occurs. An example of such an application would be the garage door. A solenoid keeps the garage door locked down until a signal reaches it to release the door – to allow a vehicle to go in or out – a simple operation as long as the door operates as intended. However, there may be times when the door does not, and one of the reasons could be the solenoid failing to activate.

If the solenoid is easily accessible, the movement of its plunger or parts attached to it can indicate whether it is functioning as intended. However, some solenoids must be located at remote locations that are difficult to reach and therefore, pose difficulties for visual fault diagnosis. However, there is a way to remotely sense whether there is proper plunger movement when the solenoid is switched on.

Many types of valves, relays and contactors use electromechanical solenoids. Typically, these operate from 12-24 V DC and 110-230 V AC systems, consuming power ranging from 8-20 Watts. Electromechanical solenoids consist of a movable iron or steel slug named the plunger or armature, and an electromagnetically inductive coil wound around it.

During actuation, when the plunger has to be pulled into the coil, the solenoid needs high current. Once actuated, the solenoid can hold the armature in the pulled-in position with only about 30% of its nominal current – this is called the hold current. If the solenoid coil consistently operates at the nominal current, high power dissipation raises the temperature of the coil and plunger. Therefore, immediately after the plunger has moved, reducing the current to the hold current helps to reduce power consumption and minimize the temperature rise in the solenoid. This is another reason to detect the plunger movement in a solenoid.

Two popular methods used to detect plunger movement depend on one, Hall sensors and two, on excitation current profile. However, Hall sensors cannot detect faulty or slow movement of the plunger, while the excitation current profile depends on the working temperature of the solenoid. Therefore, these are not particularly suitable for detecting faulty operation of solenoids.

A third and more reliable method of detecting plunger movement in solenoids depends on the current profile from the Back EMF generated by the movement. The solenoid operates when an excitation voltage energizes the solenoid coil. Current passing through the coil causes a distribution of magnetic flux through the plunger. The current increases until the magnetic flux is strong enough to move the plunger.

As soon as the plunger starts to move, its movement produces a magnetic flux in opposition to the main magnetic flux. This induces back EMF in the solenoid coil opposing the excitation voltage – momentarily reducing the current through the coil. Note that this reduction happens only because of the plunger movement and not because of anything else.

Temperature does not affect the dip seen in the current due to plunger movement. Hence, this method is a reliable indication of detecting plunger movement in solenoids.

Raspberry Pi Can Keep Your Plants Happy

Those who like indoor plants know how important it is to maintain a proper atmosphere for the plants to grow happily. Only a few parameters are important – air humidity, air temperature and soil moisture apart from adequate sunshine. However, it is rare for people to be able to monitor the health and well-being of their flora personally, given the busy schedules.

That is where a single board computer such as the Raspberry Pi or RBPi can help. Being flexible in setting up and connecting to the various sensors necessary, this SBC not only looks after the plants, but also alerts you with SMS and via email whenever the situation differs from the normal. This project also has an app, Plant Friends, for your Android phone, so that you are up to date on the real-time and historical parameter data on your plants. The project consists of three main components – the sensor nodes, the base station and the app.

You need a sensor node for each plant. Each of these sensor nodes consist of an Arduino clone called Moteino fitted with an RF transceiver, a battery meter, a temperature sensor, a humidity sensor and a sensor for soil moisture. The sensor nodes collect the readings from all the sensors and transmit the data using the transceiver to the base station. The sensors and the base station are connected via the 915MHz ISM band.

For this project, users must be slightly above the beginner level. Some basic experience with Arduino hardware and Arduino IDE will be necessary – for installing libraries, making LEDs blink, etc. Additionally, experience in wielding a soldering iron is also necessary. On the RBPi side, it is essential to be familiar with the basic knowledge of the SBC and with installing the Raspbian OS.

The Plant Friends system has several advantages. It reminds you to water your plants and sends you an alert via email and/or SMS. It works for multiple plants at the same time, even if they are in different rooms of your home. Since wires are a minimum and all components of the system are of a reasonable size, you can move the plants and the system freely about the home.

The entire system consumes low power and therefore runs on batteries. Typically, battery swaps are necessary every 4 to 6 months. The electronics is low-maintenance as it is housed in a moisture-proof enclosure. The best part of the system is the Android app, as it allows monitoring from anywhere in the world.

An RBPi, model B, is used for the project, although a model A will work equally well. However, model B has more RAM and an Ethernet port, which may be necessary for flexibility. A USB Wi-Fi adapter helps to connect to the internet.

For each sensor node, you will need a holder for four AA type rechargeable batteries. In addition, you will need a combined sensor for temperature and humidity. For sensing the moisture in the soil, you may use a soil probe consisting of a PCB with exposed traces. However, ensure there is no lead involved.

Why Do ICs Need Bypass Capacitors?

Any electronic design engineer will vouch for the necessity of supplementing integrated circuits on their PCB with bypass capacitors, although they may not understand the reason to do so very well. As a rule of thumb, engineers provide every IC with a 0.1µF ceramic capacitor next to its power pins in each circuit board they design. Along with proper PCB layout techniques, adding a bypass capacitor improves circuit performance and maximizes the efficacy of the ICs.

The trouble lies with transition currents. Circuits handling digital signals produce rapid transitions when their signals switch states. When digital circuits output a high state, the signal voltage is very close to the supply voltage. When they output a low state, the signal voltage reaches very near the ground voltage. When transiting from a low to high or a high to low, the voltage swing from supply to ground or from ground to supply, causes a transient current to be drawn from the supply.

Usually, power to an electronic circuit on a PCB is fed at a single point and traces on the PCB carry this power to each IC. Traces on the PCB have their own parasitic inductance, which, when coupled with the source impedance of the power supply, react to transient currents by creating voltage transients.

The trouble aggravates when ICs have to drive low-resistance or high-capacitance loads. The low-resistance demands high currents when the digital state changes from low to high. Again, when the digital state changes from high to low, there is a demand for the load current to reduce suddenly. However, according to Lenz’s Law, an induced current will flow such as to oppose the change that produced it.

The net effect of transient currents and the parasitic inductance of PCB traces and wires are to create high-magnitude voltage transients, ringing or severe oscillations in the power lines. This can lead to suboptimal circuit performance or even to system failure. Engineers at Texas Instruments have demonstrated an improperly bypassed line driver IC switching at 33MHz can induce ringing amplitude of the order of 2V peak-to-peak on a 5V power rail.

Placing a 0.1µF ceramic capacitor close to the IC power pins improves the situation, because capacitors store charge. Placing the bypass capacitor close to the IC allows low resistance and series inductance. The bypass capacitor is therefore in a better situation to supply or absorb the transients on the PCB traces, which have a comparatively larger resistance and series inductance.

Although engineers refer to such components as both bypass and decoupling capacitors, there is a subtle distinction between the two terms. Decoupling refers to the amount by which one part of the circuit influences another. Bypassing provides a low-impedance path allowing noise to pass by an IC on its way to ground. A capacitor, placed close to the IC supply pins, accomplishes both decoupling and bypassing. However, a decoupling capacitor has an additional task. It blocks the DC component of a signal and prevents it from traveling through to the next part of the circuit, while allowing the AC component little or no resistance at all.

Keep Your Fish Happy with a Raspberry Pi

People who keep fish in aquariums at home know it is important to feed them timely and to keep their habitat clean. Trouble starts when the owner has to leave home for a few days and cannot find a knowledgeable caretaker to take care of the pets. Cabe Atwell tried to solve the problem he faced in an ingenious way – by using the power of the Internet.

Cabe had an automatic fish feeder, but he also enlisted the services of a friend to keep an eye on her goldfish, the friend was not sure of what was required and the automatic fish feeder broke down. Fortunately, the losses were not fatal, but Goldie the goldfish grew to double her size because of overfeeding. This led Cabe to work on a system to allow watching and feeding the pet over the Internet.

Cabe wanted a system that would allow seeing the fish in real time, anytime, by moving a camera around the tank. The next requirement was sensing the tank water temperature and cutting off the power to the tank bubbler and air filters, if necessary. It was also necessary to feed the fish manually, and above all, to do this through a network and ultimately, via the Internet.

Cabe’s research led to the conclusion that a Single Board Computer such as the Raspberry Pi or RBPi and a Pi camera would be most suitable for seeing the fish via the internet. For the other features, an Arduino Uno was more appropriate.

Accordingly, Cabe selected two small Nema 17 mount stepper motors, available on Adafruit, for the driver components. The motor controls came from an Arduino Motor Shield, which made it simpler to drive the motors. Cabe designated one motor for allowing movements in two directions, while the other rotated the food container to dump fish food into the water.

The fish feeder was a modification of the original malfunctioning feeder. It consisted of a drum to hold the fish food. When rotated completely around, a simple trap door opens briefly to let a small amount of feed.

To keep the camera motor traveling too far, Cabe incorporated limit switches in both directions. The limit switches were placed in position using rare-earth magnets, which allowed easy adjustments for the movement range. A surplus belt driven motion platform provided an affordable arrangement for viewing the entire length of the tank.

For sensing the water temperature, a waterproof digital temperature sensor was the most suitable – DS18B20. Although fresh-water fishes are more tolerant of water temperature variations, loss of air-conditioning or heating arrangement can lead to the tank water becoming too hot or cold for the comfort of its occupants.

For the video stream, Cabe settled on VLC since it was easier to use. VLC offered the maximum resolution of 640×480 pixels at 15 frames per second, which Cabe found adequate for keeping a tab on the fish. A simple AC relay took care of feeding power to the air filters and bubbler.

For the future, Cabe wants a better AC control and more sensors for measuring the pH, ammonia and nitrate levels in the water.

How Does Switching Affect Semiconductors?

Even though ICs rule the world of electronics, the transistor does all the work. Within each IC are millions upon millions of transistors perpetually switching on and off so that the IC can carry out its intended functions. Even if one of the multitudes of transistors were to stop switching, the IC could lose part or all of its functionality.

Circuits handling digital signals most often use transistors to switch from a high state to a low state and vice versa. It is usual to call a circuit point as being in a high state if the voltage at that point is close to the supply voltage. If the circuit point is closer to the ground or zero voltage, we generally call it as being at a low state. The time taken for the transistor to switch from a high to a low state or vice versa is its switching rate. While the transistor does not expend much energy when at either the low or the high state, the same cannot be said for the time when it is actually switching.

Under ideal conditions, a transistor should switch instantaneously. That means the transistor should take zero seconds to change its state. However, ideal conditions do not happen in reality and the transistor takes a finite time, however small, to actually switch over.

Transistors are made of semiconductor material and each junction has a finite capacitance and resistance. Junction capacitances store energy and the combination of resistance and capacitance acts to slow down switching – the capacitance must fill up or empty itself before the transistor can flip. The rate at which the capacitance fills up or empties itself depends on the junction resistance.

The situation gets worse as the switching frequency goes up. As the transistor is driven to toggle faster and faster, the junction capacitance may not get enough time to discharge or charge up fully. That defines the maximum switching rate the transistor can achieve.

Semiconductor manufacturers use various methods to reduce junction capacitances and resistances to induce these special semiconductors switch faster. Although modern semiconductors (transistors and diodes) are capable of switching at MHz or GHz scales, the cumulative effect of the tiny switching losses add up to increase the junction temperature.

Power is the product of voltage and current. When a semiconductor is in a high state, although the voltage is high, the current is negligible and consequently, the power drawn from the supply is negligible. When the semiconductor is a low state, its voltage is close to the ground level and the product of current and voltage is again negligible.

However, during switching, when the voltage is somewhere in-between the supply and ground levels, the current drawn also increases. That makes the product of voltage and current have a significant value and the semiconductor generates heat because of the power consumption. With higher frequencies, this happens more frequently and the heat accumulates to produce higher junction temperature.

If the natural process of heat dissipation can remove the accumulated heat, the semiconductor soon reaches a steady temperature. Else, heatsinks and or forced cooling methods are necessary to remove the heat accumulated.

What is Micro-porous Copper Foam Technology?

Apart from Aluminum, Copper is the most widely used material for making heat sinks, because properties of copper make it suitable for the purpose. Chief among them is its superior thermal conductivity and malleability. That means copper conducts heat better than most other materials and it is easy to form into different shapes that a heat sink necessitates. However, latest research has revealed another form of copper that promises still better thermal conductivities.

In today’s high-density electronics, thermal management plays a significant role. Reducing heat generation and removing heat from tight spaces is a constant challenge for electronics engineers designing smartphones, laptops, tablets and other space-constrained gadgets.

Engineers manage the heat generated in such high-density electronic designs by deploying optimized heat sinks. Versarien, a materials specialist, has found that using a micro-porous structure of copper maximizes its surface area enabling the heat sink become more effective in dissipating heat.

Micro-porous copper or copper foam has pores that vary in size from 300 to 600µm. The pores also make it lighter than solid copper, with a relative density of around 37%. Most importantly, the pores increase the surface area much more than that in traditional copper foam. A lost carbonate sintering process is responsible for generating the micro-pores.

Metallurgists compact and sinter a mixture of pure copper powder with a carbonate powder. This makes a matrix of copper ligaments, with the carbonate powder sandwiched in between. Once the mixture cools, water dissolves the carbonate, which is then recovered for recycling. The remaining copper forms a regular and uniform structure, which is highly rigid, porous and permeable and whose density per unit volume the manufacturer can easily control.

At present, Versarien makes heat sinks in form factors ranging from 10x10x2 to 40x40x5 mm. The company anticipates micro-porous copper foam heat sink usage in VOIP equipment, broadband routers, cable modems, flat panel displays, set top boxes and Gigabyte Passive Optical Network communication infrastructure.

Micro-porous copper foam is like an open cell structure, with an extraordinarily large number of interconnected pores distributed uniformly throughout the base copper material. To enhance its radiant properties, the manufacturer deposits a thin but exceedingly hard copper oxide coating at a high temperature. That gives the copper its high emissivity so desirable in a heat sink. Overall, you can have a significant height reduction in a passive heat sink footprint, without any compromise on its capacity to remove heat.

Testing provides evidence of its superior efficiency in heat removal. Micro-porous copper foam heat sinks outperform traditional solutions by more than 6°C/W. That means for every Watt of heat removed by a micro-porous copper foam heat sink, there is an additional temperature drop of about 6°C above what is offered by traditional heat sinks. For example, the thermal resistance of a 40x40x5 mm micro-porous copper foam heat sink is 17.4°C/W for an applied load of 5W. For a 20x20x5 mm heat sink, the thermal resistance is 35.8°C/W for an applied load of 2W.

Conventional heat sinks require special appendages such as pins, fins or micro-channels to increase their surface area. That increases the space taken up by the heat sink and makes it less efficient. When available space is limited, it is more practicable to use micro-porous copper foam heat sinks.

Leap Motion with the Raspberry Pi

Robots have the capability to work where humans would find it inconvenient. In fact, that is one of the reasons people build robots. For example, in areas where high amounts of nuclear radiation would be fatal for a human being, a robot can work happily. Science fiction movies have exploited this feature several times – a robot mimicking the hand movements of its human controller, when watched and manipulated from a safe distance. Now, with a few motion-controlled servos, Leap Motion and Raspberry Pi or RBPi, the tiny Single Board Computer, you too can make a robot with the ability to mirror the movement of your hands. Additionally, you can do this even when you are sitting on the opposite side of the Earth.

The project involves two servos, each mirroring the movement of your individual hands. A Leap Motion controller captures the motion of your arms and sends appropriate instructions to the RBPi, which drives the two servos using a PWM driver. Two 8×8 RGB LED matrices individually attached to the servos react to each finger movement on your hands. The Leap Motion controller communicates with the RBPi via PubNub Data Streams.

The project uses the RBPi Model B+, Leap Motion controller with Leap Motion Java SDK, four numbers of Tower Pro Micro Servo, the Adafruit PWM Servo Driver and an optional display case.

The Leap Motion controller is a powerful device. It is equipped with three infrared LEDs and two monochromatic IR cameras. The cameras capture the movement of your hands and Leap Motion publishes their attributes to a channel via PubNub. The Leap Motion SDK has the attributes pitch, yaw and roll pre-built in it and actually separates the movements of your hands into the three attributes.

For achieving real-time mirroring, Leap Motion sends the attribute information messages nearly twenty times in a second. It sends information about your individual arms and each of your fingers to PubNub. Since the RBPi subscribes to the same channel, it is able to parse these messages for controlling the servos and the RGB LEDs.

To start, you will need to open a Java IDE and create a new project. You will find a guide for the Leap Motion Java SDK here. Follow up this step with installing the PubNub Java SDK. Make your project implement Runnable, which will allow all the Leap activity to operate in its own thread.

Every second, Leap Motion captures nearly 300 frames. Each frame has a huge amount of information about the hands, such as the number of fingers presently extended and hand gestures such as pitch and yaw. To simulate the motion of the hands, one servo mirrors the pitch while the other mirrors the yaw. Incidentally, pitch is the rotation around the X-axis and yaw is the rotation around the Y-axis. Both servos rotate 180-degrees with a sweeping motion. The resulting servo mimics most of the movements your hands make.

Leap Motion outputs values for the pitch and yaw in radians. The RBPi is responsible for converting these radians into degrees and finally into PWM or pulse width modulation between 150 and 600 MHz for driving the servos.Leap Motion with the Raspberry Pi

Is Your Solar Panel Installed the Right Way?

Although few people would have noticed, the costs of solar photovoltaic cells have been dropping over the years. As the technology took off, costs plummeted in the first 12 years. However, between 2005 and 2009, global market demand surged, making it difficult for supply to keep up. As manufacturing picked up post 2009, solar PV cell prices have continued their downward trend steadily. Now, it makes sense for companies to switch to PV cells purely based on economics.

As solar grows to become a more attractive option, we see a clear preference in its adoption over adding new wind capacity. Navigant Research has predicted in their recent report that declining prices will result in the global solar PV market exceed $134 billion by 2020 – a phenomenal increase of 50% from this year. That means a solar capacity addition of nearly 435 Gigawatts.

However, getting the maximum benefit from solar PV cells requires mounting them the right way. As the sun traverses the sky in the daytime, the PV cells must either follow the trajectory of the sun or be mounted in the most optimum way for them to catch most of the sunlight. Automatically turning the PV cells to face the sun requires elaborate sensing and expensive movement mechanisms. Therefore, most people prefer fixed installations that are simple to put up and maintain.

Another thing to consider is the latitude tilt of the location where you intend to install the solar cells. If your location is below the 25 degrees latitude, tilt the solar panel towards the sun the same amount as the latitude number. At 25 degrees latitude, your panel must tilt by 25 degrees. Above 25 degrees, you will need to add five degrees for each additional five degrees of latitude up to 40 degrees. At and beyond 40 degrees latitude, add 20 degrees of tilt to the latitude number. The above is the general thumb rule people follow for solar PV panel installation. Consequently, most installations have the solar panels facing south to catch the maximum amount of sunlight.

Researchers at the Pecan Street Research Institute have discovered ways to additionally fine-tune the positioning and tilt of the solar panels to extract somewhat more power. During their research on impact of residential solar power on the power grid, they discovered that if the solar panels faced west rather than the customary south, they could generate about 2% more power.

So long, homeowners, utilities and architects believed that in the northern hemisphere, solar panels directed south would receive the maximum exposure from the sun. However, when studying home installations in Austin, Texas, Pecan Street researchers found that this was not true. In fact, they noticed south-facing panels generating less energy. They found west-facing panels generated more power in the afternoon, when the energy demand peaked.

As energy demand peaks, a typical home in Austin using solar panels reduces its reliance on the power grid by as much as 54%. However, for homes with west-facing panels, this number shot up to 65% – a significant power saving. Therefore, by merely shifting the angle, you may be able to achieve significant gain in solar power generation.

What is Hyperscale Cooling?

We are more familiar with heat generation in electronic gadgets and methods followed for its removal. Heat sinks are commonly recognized for their function – removing unwanted heat by conduction and convection. Most engineers know how to keep the temperature of the components on their printed circuit boards such as ICs below some maximum allowable value. They are also aware of the heat within the overall enclosure, which may be for a standard rack of boards, a power supply, or a DVR.

Engineers follow several techniques to remove heat from ICs, boards, or enclosures. These often involve the use of one or more heat sinks, heat pipes, heat spreaders, cold plates, and fans. Methods that are more sophisticated use active cooling approaches that include air conditioning or cooling with liquid flowing through embedded pipes. All these are good techniques for handling heat generated with a few kilowatts of power.

However, things change when megawatts of power is involved. Consider for instance, a hyperscale data center that offers a massively scalable compute architecture. Usually made up of small, individual servers called nodes, the hyperscale data center provides computing power, storage, and networking, with the nodes clustered together and managed to form a single entity. Inexpensive, off-the-shelf servers form the nodes. As demand increases, more nodes are attached. Although no formal standard is available as to the minimum power dissipation that can be considered hyperscale, it is safe to admit it is in the range starting at hundreds of kilowatts to megawatts.

According to thermodynamics, energy cannot be created or destroyed. Therefore, the heat removed from the object to be cooled must be delivered to another location that is willing to be heated up. Therefore, when cooling a hyperscale data center, the problem lies in dumping this enormous quantity of heat at a location that can accept it.

BSRIA, an organization involved in testing, instrumentation, research, and consultancy in the construction and building services, has recently conducted a market study. They offer a valuable insight into the cooling options and trends available to hyperscale data centers.

According to the BSRIA report summary, they have represented the feasibility and popularity of techniques versus data-center temperatures in a four-quadrant graph. Among the options shown are reducing dissipation by using modular DC power supplies and variable-speed drives, cooling techniques by using adiabatic evaporation to liquid cooling and allowing a rise in the temperature at the server-inlet. The graph includes growth potential against the investment level necessary for each approach – most popular is the adiabatic/evaporative cooling.

The adiabatic/evaporative process of cooling uses a natural phenomenon to regulate temperature. The cooler uses a large fan that draws in warm air through pads moistened with water, which evaporates. Huge quantities of heat are removed when water evaporates, chilling the air, which is then pushed out to the room. Temperature control is a simple matter of adjusting the airflow of the cooler.

For data centers and other facilities, the adiabatic/evaporative process has saved the industry millions of liters of water. Older cooling towers would pollute the water they used. Adiabatic cooling units also save greater than 40% in electricity consumption.