12 programming mistakes to avoid article shows you the dirty dozen of application development pitfalls — and how to avoid these all-too-common programming blunders.
Archive for January, 2011
Programming mistakes to avoid
Monday, January 31st, 2011Why 3D doesn’t work
Wednesday, January 26th, 2011Why 3D doesn’t work and never will. Case closed. article tells about a letter is from Walter Murch, the most respected film editor and sound designer in the modern cinema (and not a big fan of 3D). The article comments on 3D cinema: dark, small, stroby, headache inducing, alienating. And expensive.
The first problem is that the 3D image is dark (about a camera stop darker) and looks small. Somehow the glasses seem to “gather in” the image and make it seem half the scope of the same image when looked at without the glasses.
Walter edited one 3D film back in the 1980’s — “Captain Eo” — and also noticed that horizontal movement will strobe much sooner in 3D than it does in 2D. This was true then, and it is still true now.
The biggest problem with 3D, though, is the “convergence/focus” issue. The audience must focus their eyes at the plane of the screen, but their eyes must converge at different distances depending on what the illusion is. So 3D films require us to focus at one distance and converge at another. This is a deep problem, which no amount of technical tweaking can fix (unless we can change to true “holographic” images).
Read also 3D Cinema Doesn’t Work and Never Will comments at Slashdot. Read also my earlier 3D postings Why Bad 3D Gives You Headaches, 3D is dangerous?, 3D Vision Problems and 3-D is coming soon.
1G, 2G, 3G, 4G, and everything between
Sunday, January 23rd, 2011Just what is “4G,” anyway? It’s one higher than 3G, sure, but does that necessarily mean it’s better? 2G, 3G, 4G, and everything in between: an Engadget wireless primer tries to answer those and some other questions on mobile communications technologies.
Here is my “short” summary of the different generations:
1G: Analogue cellphone technologies introduces in early 1980s: AMPS in the US, TACS and NMT in Europe
2G: The early nineties saw the rise of the first digital cellular networks: GSM in Europe, D-AMPS “TDMA” and IS-95 CDMA in the US
2.5G: You know you’re in trouble when you need a decimal place! GPRS packet data introduced to GSM system in 1997.
2.75G: EDGE was conceived as an easy way for operators of GSM networks to squeeze some extra juice out of their 2.5G networks
2.9G: Same EDGE that some call with name 2.75G. Now you know how in trouble you are with a decimal place!
3G: ITU IMT-2000 standard, CDMA2000 offered CDMA networks an “always-on” data in US (1xEV-DO protocol provided 3G speeds), UMTS (WCDMA) rose to the top as the 3G choice for GSM operators
3.5G: High Speed Packet Access (HSPA) extends and improves the performance of existing WCDMA protocols, designed provide mobile broadband access of several Mbit/s to laptop computers and smartphones.
3.75G: HSPA+ provides theoretical HSPA data rates up to 84 Megabits per second (Mbit/s) on the downlink and 22 Mbit/s on the uplink through the use of a multiple-antenna technique known as MIMO
4G: WiMAX and LTE almost meet the original ITU 4G criteria and are often marketed as “4G”, former tops out at around 40Mbps and the latter around 100Mbps theoretical
5G: 5G (5th generation mobile networks or 5th generation wireless systems) is a name used in some research papers and projects to denote the next major phase of mobile telecommunications standards beyond the 4G standards (expected to start being used around 2020), expected to offer peak download and upload speeds of more than the 1 Gbps
For years you’ve probably seen people argue that WiMax or LTE technically is not true fourth generation (”4G”) wireless because it didn’t meet certain criteria. Although LTE is often marketed as 4G, first-release LTE does not fully comply with the IMT Advanced 4G requirements. Since the International Telecommunications Union had never set a standard for what 4G was, it was a little hard to make any qualification. LTE, WiMax Now Officially Not Technically ‘4G’ article tells that ITU has officially come out with a statement declaring that only WiMax 2 (802.16m, or WirelessMAN-Advance 2) and LTE-Advanced can technically be declared “4G”: “Harmonization among these proposals has resulted in two technologies, “LTE-Advanced1″ and “WirelessMAN-Advanced2″ being accorded the official designation of IMT-Advanced, qualifying them as true 4G technologies.”
Everything LTE is a brand new microsite from Test & Measurement World dedicated to the long-term-evolution (LTE) wireless technology market. It features insightful blogs industry news, videos, whitepapers, case studies, etc. Interesting looking site.
Dancing robot
Friday, January 21st, 2011Friday special: Hexapod: Best of Dance 2009
New HTML5 logo
Wednesday, January 19th, 2011The Worldwide Web Consortium has unveiled its HTML5 logo. W3C promotes HTML5 with new logo. Here is the HTML5 logo:
The irony is that the logo is meant to clear up confusion over the HTML5 moniker. And much like Apple, Google, and Microsoft before it, the organization that oversees HTML5 has confused it with all sorts of other web standards according to W3C tackles HTML5 confusion with, um, more confusion. The W3C’s new HTML5 logo is a “general-purpose visual identity” that denotes HTML5, CSS, SVG, WOFF, and other technologies used to build web applications.
The hype over HTML5 hit epic proportions last year when it was used in Steve Jobs’s jihad against Adobe Flash. Google had said much the same thing – except for the Flash-is-dead bit. Apple and Google have already grouped all sorts of non-HTML5 technologies under the HTML5 umbrella. Also Microsoft has joined this unreality.
HTML5 seems to becoming “unhinged from reality“. W3C has stepped in to clear up the confusion. Except that it hasn’t. Please stop this. HTML5 is HTML. CSS3 is CSS. etc..
Is HTML5 becoming a meaningless marketing term? Badge of shame blog posting comments: “It’s about HTML5,” that will soon be as meaningful as saying “It’s about Web 2.0,” or “It’s about leveraging the synergies of disruptive transmedia paradigms.”
Prototype PCB ideas for RF parts
Tuesday, January 18th, 2011Using low-cost PCBs (printed-circuit boards), you can easily design a board in a few hours with nearly any CAD packag (even the free ones). Most suppliers can fabricate a PCB with line width and spacing down to 0.006 in.
Make a quick-turnaround PCB for RF parts article tells that RF circuits usually need 50Ω traces for proper circuit operation. Parts get smaller, but the laws of physics don’t change. Thus, a microstrip trace on a 0.062-in.-thick standard prototype board that was calculated to be 0.11 in. wide 30 years ago is still 0.11 in. wide today. Many surface-mount parts are far smaller than their predecessors, so two-layer prototype boards for RF prototyping easily seem to be unsuitable for today’s small SMT (surface-mount-technology) parts.
Make a quick-turnaround PCB for RF parts article tells also one promising alternative. You can use a CPWG (coplanar-waveguide-over-ground) structure to build 50Ω RF traces on PCBs. A CPWG structure lets you make the required trace width smaller than that of a microstrip structure. This approach is better than using a 0.11-in.-wide trace and is compatible with SMT-sized parts.
This is a good reminder that microstrip is just one of the techniques to use for microwave and other RF circuits. The advantages of coplanar waveguide are that active devices can be mounted on top of the circuit, like on microstrip. GCPW can provide extremely high frequency response. The main reason that CPW is not used is that there is a general lack of understanding of how to employ it within the microwave design community and a lot of CAD programs don’t support it.
There are on-line calculators for Coplanar Waveguide Calculator and Grounded Coplanar Waveguide. Coplanar Waveguides (both with and without ground) can be seen in use on modern electronics circuit boards.
Web browser gaming
Friday, January 14th, 2011Mozilla wants to see the web browser as a new gaming platform in addition to normal browsing use. Mozilla Labs Game On is all about games built, delivered and played on the open Web and the browser. Out of the 160+ submissions to the first competition, 124 games have been selected to be showcased in the Game On Gallery. You can play games being hosted on Mozilla Labs or author’s own server.
The games usually execute Javascript so run on your local machine, but the servers are still being hammered heavily on bandwidth when lot of people are downloading the games to their browser (like normal web pages). You can vote for the best game (you need to register to be able to vote). Notice that the source code of many games is available, so this could be as well a learning experience besides gaming fun.
Mobile phone repair tips
Wednesday, January 12th, 2011I had to do some repairing for Nokia N73 mobile phone. The problems were on some buttons and charging connector. Mobile phones can be tricky to open and often use special component, which can make repairing sometime hard unless you know exactly what you do.
A real goldmine for anyone attempting to star repairing a cell phone nowadays are disassembly/assembly videos on Youtube. The
N73 Assembly & Disassembly Video by Poojara Telecom Pvt. Ltd. (e-mobileguru) video revealed everything needed to know how to disassemble the phone, where the parts to be repaired are and how to finally assemble the phone. There were several videos on N73 disassembly, so I looked quickly several of them to make sure that the video I plan to follow is real and not any joke or something.
Next I needed some tools. I already had some suitable tools for opening the phone ordered from Dealextreme. You really need this kind of tools made of plastic material to avoid scratching or otherwise damaging the mobile phone case.
In addition to those I those I needed tweezers and a small torx screwdriver to do the dis-assembly. Then for actual repair I also needed a new charger connector which I found from KCL Finland for few Euros.
The rest of the task was pretty straightforward task of following the instructions on the video. Phone got repaired.
Communicating LED lamps
Friday, January 7th, 2011LEDs are used for a long time for all kinds of data communications applications ranging from wireless IR remote controls and IrDA to wired fiber optics communication. There has been many years ago also ideas on optical wireless LANs based on infrared, but they faded quickly. But now when LED lights are becoming very popular this idea could see a second coming.
Ceiling lights in Minn. send coded Internet data article tells about LED lights that will transmit data to specially equipped computers on desks below by flickering faster than the eye can see. The first few light fixtures built by LVX System will be installed in six municipal buildings in the central Minnesota. The LVX system puts clusters of its light-emitting diodes in a standard-sized light fixture. The LEDs transmit coded messages A light on the modem talks back to the fixture overhead, where there is sensor to receive the return signal and transmit the data over the Internet. It works in almost exactly the same way that fiber optic systems do, except the sender and receiver aren’t connected by a cable. Communicating lights are set up using just ordinary power connections. The first generation of the LVX system will transmit data at speeds of about 3 megabits per second. If you are interested check video from Get ElectricTV.
There is another application that also combines wireless communications and LED lights. Finnish article Wlan ohjaa yksittäisiä led-loisteputkia (read English translation) tells about LED light tubes can be controlled by a WLAN connection, even individually. Finnish company Valtavalo has licensed Netled control technology from Yashima Dengyo Co., Ltd. and sells their products. Netled technology is designed to provide means to monitor in electricity consumption in real time and control the various LED light tube groups.
Lamp vs LED power
Tuesday, January 4th, 2011When visiting Motonet show one day I saw LED light bubs display with following match for LED bulb power to classic light bulb watts (similar idea as in energy saving lamps matches certain watts normal bulb). The power ratings I saw was: 1.3W LED would match 13W normal bulb. And 2W LED would match 20W bulb. And so on.
Sound like about right as general rule of thumb for LED products now. But keep in mind that the efficiency of LED bulbs vary considerably depending on how light bulb is built and what components are used in it (and products will continue to change over years). One example is that a 7W LED bulb (at 560 lumens) can serve as a replacement for a typical 500-lumen 40W incandescent bulb.
I have earlier written about LED car bulbs. A 55w halogen should typically be putting out 500 to over 1000 lumens. A good 3.4w led would be about 250 or less. So something like 3-4 of such LEDs would be needed to the same output as 55w halogen gives out.
The Great Internet Light Bulb Book says about light bulb lumens:
In a 120 volt, 100 watt “standard” bulb with a rated light output of 1750 lumens, the efficiency is 17.5 lumens per watt. This compares poorly to an “ideal” of 242.5 lumens per watt for one idealized type of white light, or 683 lumens per watt ideally for the yellowish-green wavelength of light that the human eye is most sensitive to.
Most household incandescent bulbs have efficiencies from 8 to 21 lumens per watt. The reason for this poor efficiency is the fact that tungsten filaments radiate mostly infrared radiation at any temperature that they can withstand. Higher efficiencies near 35 lumens per watt are only achieved with photographic and projection lamps with very high filament temperatures and short lifetimes of a few hours to around 40 hours.
