A fractal is a figure with a self-similar pattern. Usually the fractals are calculated with a computer, but is is possible to produce Fractals without a Computer! It’s very cool – partly because it looks neat, but also partly because it shows you something important about fractals.
Optical video feedback is a well-known phenomenon. If you hook a camera up to a TV and then point it at the TV, you get an infinite regression of images. I remember playing with this effect at 1980’s when first time playing with video camera. You can get some interesting effect in this way (was cool at that time, nothing spectacular at today’s standards when computer special effects are widely used in videos).
This video shows that you can use the same feedback phenomenon with multiple displays to make fractals.
Android USB accessories are specifically designed to attach to Android-powered devices and adhere to a simple protocol (Android accessory protocol) that allows them to detect Android-powered devices that support accessory mode.
Prosessori magazine just published my article on Android mobile operating system in it’s newest 05/2011 issue. The article is written in Finnish and now available only on printed magazine (later available on-line for subscribers). The Android links to products and resources mentioned on the article are available on-line on Prosessori web pages, check them out.
Braben has developed a tiny USB stick PC that has a HDMI port in one end and a USB port on the other. You plug it into a HDMI socket and then connect a keyboard via the USB port giving you a fully functioning machine (700MHz ARM11 with 128MB of RAM) running Ubuntu version of Linux. This tiny computer is promised to handle web browsing, run office applications, and give the user a fully functional computer to play with as soon as it’s plugged in. You can attach a 12MPixel camera module to it as shown on the following picture from Raspberry Pi Foundation web page.
Sounds interesting cheap Linux platform. Let’s hope this becomes available soon and at promised price. I can think many uses for this kind of cheap, small and low power consumption Linux platform.
UT81B from Uni-Trend is a scopemeter. It is a multimeter with some basic oscilloscope functions.
This multimeter can measure what you expect from a normal multimeter: DC V up to 1000V, AC up to 750V, resistance up to 40Mohm, frequency up to 10MHz, capacitance 100uF, AC/DC current 10A (and of course it has also a diode and continuity test). The measurement inaccuracy is overall around 1% according to documentation which is pretty acceptable figure.
The magic lies in the embedded oscilloscope functionality. When you need more than just multimeter reading, you can press a button and get oscilloscope view. In oscilloscope mode bandwidth for UT81B is 8MHz with 40MS/s giving resolution 100ns/div – 5s/div with 8bit ADC. You can do the oscilloscope measurements with normal multimeter leads (OK for low frequencies) or use adapter for real oscilloscope probe (for accurate measurement of higher frequencies).
Oscilloscope together with the multimeter is pretty ideal tool for the technician for reparations on the spot as well as for other professionals in workshops. Possibility to be powered by batteries turn this instrument in an ideal tool to be used as a mobile meter. LCD monochrome display with 160 x 160 pixels is very easy to read thanks to the back-light function.
The “Auto-Set” key allows to work very quickly and easily without too much trouble going through settings menus, although I must say that the automatic range setup is pretty slow (it can take more than 10 seconds for the meter to find appropriate vertical and horizontal range). Fortunately there is the manual mode so you can set the range and timebase yourself if you know in advance what to expect. Overall, for an 8MHz and 40MS/s scope the performance is very good.
Meter is best suited for measuring of larger continuous signals. You can stick it directly to mains power for example without worrying ab out anything. For very low level signals you can easily see interference on the measurements. Measuring on-off events on the scope screen is a bit hard also. One thing I noticed is that multimeter and oscilloscope seem to use pretty much separate electronics inside the device: multimeter part has pretty limited bandwidth while oscilloscope has high bandwidth. When you are working for example at 50 Hz mains power, scope and multimeter readings show about he same. But when measuring signals at many kHz frequency, scope still shows signal amplitude correctly, but multimeter reading shown on the screen is pretty much off from the right value. So multimeter voltage reading is just for DC and low frequency measurements.
When the whole device is battery powered, it is completely floating device, so you can freely measure circuit that are connected to ground or other potential that is not ground, just like any normal multimeter. When you power the device with batteries the multimeter is completely floating, and you are free to do all types of measurements without worrying any grounding issues (like with normal grounded oscilloscope). One good plus is that you can do oscilloscope measurements also on the current measurement range (measuring current waveforms with traditional scope would need some extra adapters / tricks).
The meter looks great and build quality is good. Case is plastic with a rubber surround. UT81B is quite a brick, a slightly big for a multimeter. The software running the device is not fast, neither too slow – acceptable, but could be faster.
The package includes opto-isolated USB cable, safety probes, safety banana to BNC converter, alligator clips, mains power supply, manual, CD with software for reading scope data, Uni-T 1 year warranty card and a zippered case.
Attached probes are OK, although crocodiles are quite big with lot of force. If you want to measure small components get other extra probes. There is some free space on the zippered case, so you can fit in some of your own probes. AC adapter option is a good plus, because batteries last only few hours of continuous measurement.
UT81B has optically isolated USB transfer cable. There is software that allows you to do measurements. Attached CD contains software for all UNI-T meters, but of course only for Windows. This software is not the best possible. I could not get the software that came with the device to work on my Windows Vista PC. I was lucky to find a newer version of the software for download, and after some hacking (running with administrator rights) I got it finally working. Not the most reliable or use friendly software, but works acceptably.
I found that lowlever blog UNI-T UT81B posting has description of UT81B protocol. This could be useful if you are planning to write your own software that communicates with this meter. The communication is serial port communications (9600 ,n ,8 ,1) over USB.
To enable for the current command shell, right-click on the title bar, select properties, select the options tab and check the QuickEdit Mode box.
To copy text into the clipboard, select text with the left mouse button and press Ctrl-C To paste text into the command box, right click the mouse. Also selecting text with the left mouse button and pressing right click the mouse twice works if you want avoid the need for keyboard.
There are also other ways to enable this quick edit mode. Enable Quick Edit Mode in Windows XP Command Shell article gives a Windows NT / Windows 2000 / Windows XP registry hack to control the mode globally (looks promising although I have not tested this later option).
You wouldn’t write your username and passwords on a postcard and mail it for the world to see, so why are you doing it online? Every time you log in to any service that uses a plain HTTP connection that’s essentially what you’re doing.
There is a better way, the secure version of HTTP—HTTPS. HTTPS has been around nearly as long as the Web, but it’s primarily used by sites that handle money. HTTPS is the combination of HTTP and TLS. Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide communications security over the Internet.
Web security got a shot in the arm last year when the FireSheep network sniffing tool made it easy for anyone to capture your current session’s log-in cookie insecure networks. That prompted a number of large sites to begin offering encrypted versions of their services via HTTPS connections. So the Web is clearly moving toward more HTTPS connections; why not just make everything HTTPS?
The real problem is that with HTTPS you lose the ability to cache. For sites that don’t have any reason to encrypt anything (you never log in and just see public information) the overhead and loss of caching that comes with HTTPS just doesn’t make sense. The most content on this site for example don’t have any reason to encrypt anything.
HTTPS SSL initial key exchange also adds to the latency, so HTTPS-only Web would, with today’s technology, be slower. The fact that more and more websites are adding support of HTTPS shows that users do value security over speed, so long as the speed difference is minimal.
The cost of operations for HTTPS site is higher than normal HTTP: you need certificated that cost money and more server resource. There is cost of secure certificates, but obviously that’s not as much of an issue with large Web services that have millions of dollars. The certificate cost can be a showstopper for some smaller low budget sites.
Perhaps the main reason most of us are not using HTTPS to serve our websites is simply that it doesn’t work well with virtual hosts. There is a way to make virtual hosting and HTTPS work together (the TLS Extensions protocol Server Name Indication (SNI)) but so far, it’s only partially implemented.
In the end there is no real technical reason the whole Web couldn’t use HTTPS. There are practical reasons why it isn’t just yet happening today.
