Monthly Archives: May 2015

SSD, Magnetic or Hybrid Drives

Earlier, when we did not have much of a choice, PC storage options were limited to the largest capacity hard disk drive one could afford. Those days are long gone and today the average customer has to juggle between selecting different types of storage media apart from their capacity. Although it is fairly important to select the most optimum storage medium for a specific application, each of the drive types has their own advantages and disadvantages.

Magnetic hard disk drives have long been the default storage component for both desktop and laptop computers. Although the latest magnetic drives are very much advanced and better performing compared to their brethren from yesteryears, their underlying technology has remained mostly unchanged. Magnetic hard drives essentially consist of stiff magnetic platters rotating at high speeds paired with read/write heads travelling over their surface to retrieve or record data.

Magnetic hard disk drive technology is mature. Manufacturers now make highly reliable drives that users can purchase at much lower prices as compared with other storage options – most magnetic hard drives cost only a few cents per gigabyte. Moreover, they are available in relatively high capacities, going up to 4TB. Modern magnetic hard drives connect via the SATA or Serial ATA interface and do not require any special software for the operating system to recognize them. In short, magnetic hard disk drives are dirt-cheap, simple to operate and spacious.

However, the disadvantage with magnetic hard disk drives is their low storage or retrieval speeds compared to the SSDs and Hybrid products. The read and write speed depends on how fast the platter rotates – a 7200-RPM drive is faster than a 5400-RPM drive, but both are significantly slower than SSDs or even hybrid drives.

If you are just an average PC user sticking mostly to using mail, browsing the Web, and some amount of document editing, a standard magnetic hard disk drive should serve you fine.

SSDs or Solid State Drives are so called because unlike the magnetic drives, they do not have any moving parts – they are typically nonvolatile NAND flash memory. Although most SSDs connect via the SATA interface, there are PCI Express-based SSDs that offer ultrahigh-performances. SSDs store data and file just as any other drive does.

Since SSDs do not have any moving parts, they can operate at blazing speeds such as 500MB per second on average accessing data in just a few milliseconds. Compare this with the speed of a magnetic hard disk – 200MBps with access times just a shade below 8ms. In short, with SSDs you have a much snappier and a much more responsive system. With SSDs, everything is faster – boot times, application launch times and file-transfer speeds.

Without moving parts, SSDs are not susceptible to damage or degradation due to movement or vibrations. The two disadvantages with SSDs are their cost per gigabyte and their read/write life. At present, they cost about $1 per gigabyte.

Manufacturers offer Hybrid drives as a go-between. These are mostly magnetic hard drives with some SSD thrown in. The most frequently accessed data is stored in the SSD. That makes for high speed while the cost is kept low.

Can a Solar Cell Store Its Own Power?

Can a Solar Cell Store Its Own Power?

Researchers at Ohio State University have invented a device that looks like a solar cell but has the ability to store the power it generates. The patent-pending device is the world’s first solar battery. On October 3, 2014, the researchers reported in the journal – Nature Communication – that they have succeeded in combining a solar cell and a battery into a single hybrid device.

The innovation is a special solar panel in the form of a mesh that allows entry of air into the battery. Another unique process allows electrons to be transferred between the solar panel and the electrodes of the battery. Light and oxygen entering the device enable chemical reactions to charge the battery.

According to Yiying Wu, Professor of chemistry and biochemistry at the Ohio State University, they will license the new solar battery to industry. Wu expects that the solar battery will tame the costs of renewable energy.

A solar panel is typically used to capture light for converting it to electricity, which is then stored in a cheap battery for later use. By integrating the two functions into a single device, installation becomes simpler and costs go down. The new solar battery may typically bring down the costs by about 25 percent.

The invention also has another advantage. The long interconnections between solar panels and its battery introduce ohmic resistance that reduces the solar energy efficiency because of heat generation when charging. Typically, about 20 percent of the electricity generated by the solar cells is wasted as heat when charging the battery. With the new design, nearly all the electricity generated reaches the battery.

Wu and his students have also developed a high-efficiency battery for use with their solar cells. An earlier designed battery, invented by Wu and his research team, won them the 2014 clean energy prize of $100,000 from the US Department of Energy. The researchers have created a technology spinoff – KAir Energy Systems, LLC – to develop the battery.

The high-efficiency battery is air-powered, meaning it breathes in air when discharging and breathes out when charging. The battery discharges by the chemical reaction of potassium and oxygen. The researchers faced a formidable challenge when trying to combine a solar panel with the KAir type of battery. Typical solar cells are solid panels of semiconductor material and this would prevent air from entering the battery.

Wu and his research team had to redesign the solar panel to make it permeable. They did this by using titanium gauze, a flexible fabric. They grew vertical rods of titanium dioxide on the fabric, similar to blades of grass growing on soil. The rods capture sunlight, while air passes freely through them and the gauze.

Normally, interconnecting a solar cell and a battery requires four electrodes – two on the solar panel and two on the battery. The hybrid design of the researchers has reduced the number of electrodes required to three.

The mesh in the solar panel forms the first electrode. Under this, a thin sheet of porous carbon forms the second electrode, while a lithium plate forms the third. Layers of electrolyte sandwiched between the electrodes forms the battery to store electricity.

XMP-1 the Raspberry Pi Robot

XMP-1 the Raspberry Pi Robot
The inexpensive, credit card sized single board computer, the Raspberry Pi or RBPi, can be teamed up with another inexpensive, credit card sized processor platform, the XMOS startKIT. The duo presents the unique possibility for DIY enthusiasts to construct robotics applications. An additional incentive – almost no soldering required.

The XMOS StartKit comes with an XMOS processor chip that has multiple XMOS cores. You can program these cores directly in C. Multiple programs will run in parallel within the XMOS cores, at high speeds and without jitter. That is exactly what the robotics applications ideally require.

The combination of the RBPi and the XMOS startKIT makes a simple mobile platform that its designer Shabaz chooses to call as XMP-1 – the XMOS Mobile Platform, version 1. Using only simple tools such as pliers, wire-cutters and a screwdriver, XMP-1 involves only low-cost off-the-shelf standard hardware. It is flexible enough to allow addition of more sensors and programming to make it more versatile than it is at present. The XMOS board communicates with the RBPi via the Serial Peripheral Interface or SPI and you can control the XMP-1 from a web browser.

Although XMP-1 can move at quite a high speed, it is preferable to keep its speed low when it is being taught a new route. The console output and the browser controls are available on the display on the web browser to generate keep-alive and status messages to help you see what is happening. Shabaz has recorded this project in three parts, the first of which deals with programming the XMP-1 that has no sensors. In part two, Shabaz conducts more XMOS startKIT experiments. These serve to establish the process of high-speed SPI communication between the XMOS startKIT board and the RBPi.

You will be able to get the XMP-1 up and running, if you simply take the code, compile it and plug it into the flash on the XMOS startKIT board and the RBPi. However, this project is useful to all types of enthusiasts apart from those only interested in constructing and using XMP-1. For example, on the site, you will get adequate help in the XMP-1 hardware assembly, controlling hardware using RBPi and using a web browser to do it from a remote location. The site is very informative for those who are new to the XMOS startKIT.

The RBPi is connected to the network via an 802.11 Wi-Fi USB adapter and handles all network activity. A small web server running on the RBPi provides feedback to the user via a web browser. The RBPi also transfers the motor control speeds it receives from the user over to the XMOS startKIT board via the Serial Peripheral Interface. In turn, the XMOS startKIT feeds the motors with the correct Pulse Width Modulation or PWM signals.

Based on these input signals, the hobby servomotors operate to allow the XMP-1 to run at varying speeds in a straight line or to take a turn. Usually the servomotors rotate to less than a complete revolution – within a range of nearly 180-degrees. The output shaft is connected to linkages that make the wheels turn a full right, a full left or anything in-between.

An Oscilloscope with the Raspberry Pi

An Oscilloscope with the Raspberry Pi
Making a full-fledged oscilloscope with a Raspberry Pi or RBPi, the unique low cost SBC, may be beyond the scope of many enthusiasts, but here is a proof-of-concept that RBPi can handle such a project. Although not a very practical oscilloscope, it does provide several oscilloscope-like capabilities. Additionally, all this comes at a very low cost and not much of soldering is involved – impressive incentives for any DIY enthusiast to start on the project.

The oscilloscope project has additional incentives for those seeking to advance their learning curve. Information available in the project and experience gathered during the execution may be reusable for applications involving analog sensing and plotting data onto a screen. It is perfectly possible to project the output onto a larger screen as the output of the oscilloscope is available to view in a web browser. Therefore, this project could also be used to display low-frequency waveforms in an environment that does not have a real oscilloscope. The RBPi oscilloscope is quite responsive and refreshes the display several times a second.

To make the oscilloscope all you need is an RBPi, an XMOS startKIT board and a few wires. The XMOS startKIT is another credit card sized board containing the XMOS multi-cored processor. When compared to other similar processors in the market, the XMOS processor comes with a host of advantages for projects that require real-time operations. This is especially true for data-logging purposes, as the chip also contains a 12-bit ADC or Analog to Digital Converter built into it. Having all this on a single low-cost board makes the whole arrangement very attractive for connecting to the RBPi.

Although a multimeter is a very useful instrument, it cannot show electrical signals varying over time beyond a certain rate. With the RBPi oscilloscope, you can do that see more than what the multimeter tells you. Of course, it is not the intention here to make an oscilloscope with all the features that a professional scope has. However, the project does offer some oscilloscope-like features such as sweep modes, trigger capability and on-screen cursors for trace measurements.

Unlike a regular oscilloscope, the RBPi scope lacks the entire front-end. Therefore, it does not possess a good sample rate, has no front-end filters, is without any AC/DC input capabilities and there are no gain adjustments. In fact, the XMOS Analog Examiner is good enough only to examine simple circuits at low speeds. The XMOS board actually collects analog data and transfers it to the RBPi over the Serial Peripheral Interface or SPI. The RBPi runs a web server and the XAE application using JavaScript and Node.js. Anyone connecting to the XAE application via a web browser can see the data plotted as a graphical curve.

The XMOS processor can run multiple tasks in parallel, thanks to its multiple cores that can execute different codes. The XMOS cores communicate with each other using the concept of channels. Additionally, the XMOS chip also has a 4-channel ADC built in. This ADC can resolve at 12-bits or 4096 points at 1 MSps or a million samples per second. For further details on this oscilloscope, refer to this site.