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Archive for October, 2011

Bitbang Ethernet

Sunday, October 30th, 2011

Implementation UDP into microcontroller Igor Atmel-UDP device:
UDP/IP infrared remote control
web page shows implementation UDP/IP on firmware level (similar as emulation of RS232 interface or USB interface).

UDP_IP_computer_infrared_remote_control

What makes it really cool is that the ethernet is bitbanged using nothing but the bare pins of an ATMEGA168. The downside is that this Ethernet implementation is 10 Mbit/s transmit-only: it cannot receive network packets. In think this is a cool hack, that could be enough for some projects.

By the way ATMEGA168 is same chip as used on Arduino Diecimila. Maybe this idea could be adapted to Arduino boards as well if the board is modufied for this (Arduino runs on 16 MHz, this circuits needs 20 MHz clock).

If you want a real full standard Ethernet interface that can transmit and receive, you need to use a real Ethernet controller for it (Ethernet chip or interface built into the microcontroller).

CCTV Ground Loop Problems

Friday, October 28th, 2011

Humming bars in CCTV system monitor image can be caused by many different factors and tracing the issue can be a pain. Video Ground Loop Interference for CCTV article at 2M CCTV Security & Surveillance Blog gives some tips how to solve ground loop problems on CCTV systems.

ground-loop-line-interference-300x249

One cause is running your cable over a high power source, so run camera wires away from power lines. Make sure to run camera wires away from power lines (a minimum of 12 inches / 30 centimeters).

Also 24vac power transformer connections can cause similar problems. The type of AC power transformers you use to power your cameras can contribute to Ground Loop problems. A ground can be introduced to your camera “Capacitively” through the power transformer windings depending on the type and construction technique used to build the AC transformer. If you get problems an old trick is to reverse the wire on the 24V AC power supply to get the bad signal to go away. Not that this reversing trick is only for 24V AC system when you know what you are doing; do not try to reverse wires on 12V DC powered systems or you can damage your power supply and/or your camera.

Another issue with ground loops are metal buildings. If you mount cameras to the side of a metal building, remember that the entire building is one large conductor. You should never connect both ends of a video cable to local grounds. To avoid grounding on camera end, some form of electrical insulation between the building steel and camera is a good idea. Video Ground Loop Interference for CCTV recommends to put a piece of wood between the camera and the wall and that will fix the interference caused by video ground loops.

If coaxial cable shields are connected together anywhere in the system, separate them if possible. Similarly remove all but one ground connection on each coaxial cable if possible. The ground is usually at the monitor end of the coaxial cable because the monitor equipment plugs into the main power supply which is grounded.

There are video ground loop isolators (or “isolation transformers”) that can help to solve ground loop problems. My Ground loop problems in video lines article gives more details on them and links to video isolator products. For DIY solutions read my Build video isolator and Build humbugging transformer blog postings.

UN wants two-thirds of the world online by 2015

Wednesday, October 26th, 2011

Broadband technologies are fundamentally transforming the way we live. UN believes that communication is not just a human need – it is a right. The greater communication and understanding made possible through access to information and communication technologies. In today’s challenging economic climate, recent research has shown that broadband infrastructure and services contribute to economic growth and promote job creation.

UN wants two-thirds of the world online by 2015 article says: Freedom to communicate is a human right – as is having a broadband connection, the UN said today.

By 2015, internet user penetration should reach 60 per cent worldwide, 50 per cent in developing countries and 15 per cent in least developed countries. They want 40 per cent of households in developing countries to have internet access.

1312903882

Governments should lift taxes on ICT services and free up radio frequency spectrum to fuel an expansion of networking, the UN recommends in its Broadband Challenge issued on Tuesday. Businesses should work out some smarter business models and the prices should come right down.

Connectivity is necessary, but not sufficient. Hand in hand with the roll-out and deployment of broadband networks, it is vital to develop new services, personalized applications and fully multilingual content to ensure that everyone finds their place in the global village online.

If this vision holds there will be lots of work for people that build and maintain the needed access networks. And there there will be lots of work to create that multilingual content.

Agile hardware development?

Tuesday, October 25th, 2011

Software developers have largely accepted the merits of agile development and commonly debate the value of one agile practice against another. Agile software development is a creative process that does not need all details to be defines in advance. Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams.

320px-Agile_Software_Development_methodology

A fundamental flaw in applying the classic waterfall model to software development is that the act of designing and constructing software cannot often be reliably defined in advance.

Agile - fig2

Will Agile methods also work in in hardware circles? Is hardware development a creative or defined process? According to Agile hardware development – nonsense or necessity? article it is difficult for the average hardware developer to offer an informed opinion on agile. While there are obvious differences between software development and hardware development, there are also significant similarities. Change happens in hardware development and there is no avoiding it.

AC current levels

Sunday, October 23rd, 2011

AC current levels

0.25mA  Maximum Leakage Current for Class II equipment in IEC 950 (Information Technology Equipment, I.T.E.) (no protective earth ground in the equipment, double insulation or reinforced insulation)

0.5mA Earth Leakage Current limit in IEC 601-1 (Medical Equipment) (this is general value, here are also other leakage current requirements in IEC 601-1)

0.5mA Perception level, tingling sensation,Perception level, tingling sensation

0.51mA UL limit used by UL for continuous 60-Hz sinusoidal current: Involuntary muscular reaction

0.75mA  Maximum Leakage Current for Class I (Hand held) equipment in IEC 950 (Information Technology Equipment, I.T.E.) (basic insulation and protective earth ground connect to case)

1mA A person can feel at least 1 mA (rms) of AC at 60 Hz

1mA Current of less than 1 mA (AC or DC) can cause fibrillation if the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode)

3.5mA  Maximum Leakage Current for Class I equipment in IEC 950 (Information Technology Equipment, I.T.E.) (basic insulation and protective earth ground connect to case)

5mA Typical GFCI limit in USA. Electric current below 5 mA is not considered dangerous.

5mA UL limit used by UL for continuous 60-Hz sinusoidal current: Involuntary muscular reaction

9mA The value of current considered dangerous was obtained experimentally, and is usually given as approximately 9 mA.

10mA Painful shock, freezing current, “can’t let go” (tetanized muscle)

10mA Residual current detector limit in use in Europe for sensitive RCDs.

20mA UL limit used by UL for continuous 60-Hz sinusoidal current: Ventricular fibrillation

30mA Typical residual current detector limit widely in use in Europe

35mA Heart rhythm affected (Ventricular fibrillation), death may occur

50mA Electric current above 50 mA is considered fatal in USA and Canada electrical safety regulations.

60mA  50 or 60 Hz AC current through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 mA.

100mA When 100mA is flowing through the body for only two seconds can cause death

200mA Above 200 mA, muscle contractions are so strong that the heart muscles cannot move at all.

1A Commonly used nominal output current for current transformers used for electrical power measurements in electrical power panels and distribution systems

2.5A Maximum allowed current for equipment that use “Europlug” (EN 50075) mains connector

5A Commonly used nominal output current for current transformers used for electrical power measurements in electrical power panels and distribution systems

6A Mains power fuse size (found on some old installations in Europe)

10A Commonly used mains outlet fuse size found in Europe (1.5 mm^2 wiring)

13A Maximum current available from electrical outlets in UK (maximum fuse size in fused plugs)

15A Commonly used mains outlet fuse size used in USA

16A Commonly used mains outlet fuse size found in Europe (2.5 mm^2 wiring)
16A Standard CEEFORM mains connector current rating (CEE 17 7 IEC 309)

20A Mains outlet fuse size used in USA for outlets (heavy loads)

25A Commonly used fuse size for incoming wire in mains distribution panels for small houses in Finland (three phase 400/230V power at 25A per phase)

32A Standard CEEFORM mains connector current rating (CEE 17 7 IEC 309)

63A Standard CEEFORM mains connector current rating (CEE 17 7 IEC 309)

125A Standard CEEFORM mains connector current rating (CEE 17 7 IEC 309)

Measure with soundcard

Friday, October 21st, 2011

Unless you add a measurement instrument to your computer, you have only the sound card as an analog I/O port. You can use the sound card to digitize ac analog voltages but only within a limited range. You can, however, add some signal processing and measure a wider variety of signals, even those that produce dc or low-frequency outputs. Here some links to sound card measurement projects:

Sound card based multimeter

HOW TO – Modify a PC sound card to allow D.C. voltage measurements

CheapChop: measuring DC with a sound card

Measuring DC with a Sound Card

Measure resistance and temperature with a sound card

Sound card thermometer/ohmmeter

“2-Pound RLC Meter impedance measurement using a sound card,” Elektor, June 2008, pg 64.

ftsoundcard

About Things We Build and Fix

Thursday, October 20th, 2011

When I was last night again fixing old Nokia N73 cellular phone (needed a touch of soldering iron to make volume button to work again) I remember this article I saw few days ago.

Are engineers early adopters? article claims that engineers aren’t early adopters of the latest technology. They are more like past the peak of the adoption curve. It’s not because engineers don’t like technology, instead it’s because engineers know how to keep older technology running longer than the general population. We fix and upgrade older technology when others simply replace it.

Me doing some small fixes to my smarphone, PC and some more electronics, is for sure keeping older technology running longer.

One Are engineers early adopters? article comment says: “Engineers are early adopters of truly new technology, but are not early adopters of trendy marketing or technology that is not a significant improvement over technology that already exists.”

I am curious by nature, so new technologies/products are first reviewed on-line, tested in the store, looked at on social networks for word of mouth/experiences then purchased if all checks out. I want to know the pros and cons of the new technology. Usually only the pros get marketed to the end consumer through reviews.

Another interesting article mentioned at Why We Love Things We Build Ourselves Slashdot posting mentions article Unfolding the IKEA Effect: Why We Love the Things We Build. The IKEA Effect refers to the tendency for people to value things they have created/built themselves more than if made by someone else. Research suggests that by asking consumers to do a little legwork, you can increase their belief in the value of the product they have created, even if it would have been better constructed by professionals. Study demonstrates that this sense of personal accomplishment is powerful on its own, without any social influence.

Would the IKEA effect hold in more complex situations? Is this the reason that open source software proponents are so “enthusiastic” about their products while the general market resists them? The proponents of them had a hand in developing them. All interesting questions for future research!

Counterfeit parts

Wednesday, October 19th, 2011

Watch out for well-made (counterfeit) chips. Counterfeit parts are big headache. Saelae tells that they noticed first that many more boards than normal were failing the functional test. The USB chip was running hot. It turned out that every last part was an old revision corresponding to a different (obsolete) part number – the parts had been relabeled with a modern part number.

Counterfeit Electronic Parts presentation from NASA gives examples of counterfeit ICs and information on business around counterfeit electronics.

chip

Counterfeit components can be a a big business and safety risk. Criminal Prosecution – Who can be held liable for the sale of counterfeit parts? is an inside look at the unscrupulous business practices that plague the open market and the liability that could accompany this unethical conduct. This article is intended to serve as a warning to sales, purchasing and management representatives involved in the purchase or sale of integrated circuits in the open market. Ignorance is not a defense. It will likely be difficult, if not impossible, for any representative of the open market to argue that they were “unaware” of the risks.

Mathematics equations in web

Tuesday, October 18th, 2011

How to present math­emat­ical ex­pres­sions using a language that has so little markup for them? Sometimes you can use MathML, but often you need to resort to images.

Useful tools and tricks article mentions a nice on-line LaTeX equation writing tool at CodeCogs.com: You type in LaTex or MathML and it creates an image of the formula. You can then take that image and put it on your website.

equationgif

You can go find most any equation in Wikipeda, then hit the “Edit” link to see the LaTex MathML type text expression. Just cut-and-paste that into the CodeCogs window and it will create the formula as an image. So code \int_a^b \! f(x)\,dx \, becomes this:

integral

For alternate tools to show equations take a look at fMath. It promises to do similar things in a different way: you can put MathML/LaTeX code inside HTML and let fMath to display it.

FPGA-based Ethernet switches

Monday, October 17th, 2011

Ethernet switches are the ubiquitous building block of any intelligent network. Ethernet technology is deployed in virtually every organization’s data center. Wide Area Networking (WAN) and Metropolitan Area Networking (MAN) providers need to provide their customers with Ethernet services. Ethernet has also become the de facto networking technology in industrial automation even in mission-critical local networks. Modern Ethernet switches have added significant new functionality to Ethernet while decreasing port prices.
switch_hp_stack_xx_nic_
FPGA-based Ethernet switches for real-time applications article tells that Lattice Semiconductor and Flexibilis have released a Gigabit Ethernet Switch IP core that is scalable, non-blocking, and extensible. The article also discusses on different Ethernet applications and requirements they need. Article tells about deterministic and synchronized real-time operation, IEEE-1588-2008 (v2) Precision Timing Protocol, redundancy, High-Availability Seamless Redundancy (IEC 62439-3) and how FPGA implementation works for those.

lat-03


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