Ultimate geeky desk sockets


Here’s a geeky desk sockets project from Luke. He writes:

I wanted a few more functions than just a desk USB Hub.
Looking on the net i came across this youtube video . This was the type of thing i was looking for but it had far too many functions and too large.
I decided to list the things i would like:

1) USB Hub (powered)
2) SD card reader
3) Basic adjustable psu
4) Mains socket
I decided rather than making something scratch i would see if there was anything available i could just modify to fit all my criteria.

Project info at Luke’s blog.

Using Altium for a DirtyPCBs order


Jarrett  has written an article describing a technique of using Altium for a DirtyPCBs order:

This is a pretty rare combo: using a premium PCB package with the budget board house.
Kinda funny.
Generally these small run PCB houses provide DRU and CAM files for EAGLE design rule checking and Gerber outputs, respectively. Because I’m using Altium, I had to make it up as I went along.
It gets much easier when you understand what Gerber files are. While we’re all used to standard, unified output formats that contain all of the data we need, Gerbers are very much still a holdover from manufacturing in the 80s.
When you export these, a whole bunch of files get generated. This is intimidating, but don’t panic! They all have different extensions like GBO, GTL, etc. These are all the same type of file.

Details at Jarrett’s blog.

Via the contact form. Thanks for the tips!

(Nothing less than) The perfect tea timer


Michael from Acidbourbon has built the “perfect” tea timer project.  He wrote a post on his blog detailing its assembly:

Maybe you just drink coffee. Then this article is not particularly interesting for you. But if you like a cup of black or green tea once in a while you might know the problem: You prepare your tea and you let it stand for a minute too long. Then it is bitter. So the next time you use the timer functionality of your smartphone … unlock the screen, open the timer app, enter something like “3:00″ (minutes), press start, pour boiling water over the tea, wait. Then your phone beeps like crazy while you are fumbling around with the hot and wet teabag you want to dispose of. Finally you unlock your beeping phone with your wet fingers, open the timer app again and silence it. Pure stress.
Of course that is a first world problem and you could just deal with it. Or if you are a tinkerer, like me, you might want to build yourself the perfect tea timer. The desired properties are:

Very small
Extremely simple user interface
When finished it plays a short melody and goes to standby by itself
Not expensive
Long battery life

Project info at Acidbourbon site.

Check out the video after the break.

STM32 FM song transmitter using tricky crystal feedback modulation


Vinod writes, “This is an FM transmitter directly made from STM32F407 discovery. It transmits the wav file stored in internal flash via FM at 100MHz.
The modulation over here is happening by a tricky feedback from the analog output of the same mcu to the crystal oscillator there by disturbing the crystal frequency and creating frequency modulation.
It works nicely than expected an getting a very good range and comparable to normal single transistor FM transmitter.

More details at Vinod blog.

Via the contact form.

Check out the video after the break.

App note: Enhancing workplace safety in hazardous locations with PICO® 259-UL913 intrinsically safe fuse


Application note from Littelfuse about their (IS) intrinsically safe fuse which doesn’t produce sufficient heat that could trigger sparks which are dangerous in an explosive environment. Link here (PDF)

Gases, petroleum products, and airborne dusts tend, by their very nature, to be explosive if sources of sparks or excess heat are present. Over the years, these hazards have led to some catastrophic losses of life and property. In response to this hazardous potential, regulatory bodies around the world, including Underwriters Laboratories, Inc., have worked to establish and refine a standard that will minimize the hazards associated with these working environments. UL 913, which was originally issued in 1971, establishes the standard for “Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations.”

The purpose of this standard is to specify requirements for the construction and testing of electrical apparatus, or parts of such apparatus, having circuits that are not capable of causing ignition in Division 1 Hazardous (Classified) Locations as defined in Article 500 of the National Electrical Code, ANSI/NFPA 70. Limiting exposure to high surface temperatures and requirements for dust-tight enclosures are key aspects of the UL913 standard.

App note: Controlling LED lighting using triacs and quadracs

an_littlefuse_littelfuse_triac_quadrac_led dimming_appnote

Solid State device and circuits for controlling LEDs lighting, replacing conventional incandescent lamps, an App note from Littlefuse. Link here (PDF)

Light Emitting Diodes (LEDs) are fast becoming the most popular lighting option. Industry forecasts anticipate the market will continue to expand at an annual rate of 20% from 2011 to 2016, with the greatest growth coming in the commercial and industrial lighting sectors. As incandescent lamps have been made largely obsolete, given the U.S. government’s mandate to save energy, they have frequently been replaced by LEDs due to their long life (typically 25,000 hrs.) and the ease of adapting them to many different socket and shape requirements. However, LED lighting control presents a few problems not encountered with incandescent lamps. For example, with much less current from the LED load, normal types of triacs may be challenged in terms of latching and holding current characteristics.

Triacs make up the heart of AC light dimming controls. Triacs used in dimmers have normally been characterized and specified for incandescent lamp loads, which have high current ratings for both steady-state conditions and initial high in-rush currents, as well as very high end-of-life surge current when a filament ruptures.

Because they are diodes, LEDs have much lower steady-state current than incandescent lamps, and their initial turn-on current can be much higher for a few microseconds of each half-cycle of AC line voltage. Therefore, a spike of current can be seen at the beginning of each AC half-cycle. Typically, the current spike for an AC replacement lamp is 6–8 A peak; the steady-state follow current is less than 100 mA.

Designing an AC circuit for controlling LED light output is very simple when using the new Q6008LH1LED or Q6012LH1LED Series Triacs because only a few components are required. All that is needed is a firing/triggering capacitor, a potentiometer, and a voltage breakover triggering device.

Measuring SDR noise figure


David has written an article on measuring SDR noise figure:

One number I wanted to know was the Noise Figure (NF) of the SDR. Mark has a bunch of SDRs so we got on a roll and checked out the NF on all of them.

Now there are a lot of people playing with SDRs, but very few tutorials on HowTo engineer radio systems. For example, how to answer questions like “can I send this many bit/s over X km with SDR hardware Y?” So I thought it might be useful to explain how we measured Noise Figure (NF) and present the results for a bunch of SDRs.

More details at Rowetel site.

A DIY wearable posture sensor


Want to improve your posture? This wearable posture sensor from Coretech Robotics will remind you whenever you slouch and help you maintain a good posture:

Posture sensors/monitors have been a recurring theme on this blog. They are supposed to remind you of your posture and prevent you from slouching, which can be a cause for back pain and headaches.While my previous sensors were either fixed to a chair or desk, this time I wanted to create a wearable version, that would allow for free movement. As always, one of the main goals was to make this project cheap and easy to reproduce.

Project info at Coretech Robotics site.

Arduino Shield for custom board CPLD programming and testing using pogo pins


Marcelo Jimenez wrote a post about a shield he did using pogo pins to program and test a CPLD based board.

The photo above shows the support for the board to be programmed with the pogo pins at the center, the board itself and the top shield. I have used two identical shield boards and have spaced them to give the pogo pins the proper vertical direction.
Some of the pads on the board to be tested are SMD, others are through hole. Of course, after it was assembled, I realized I should have left the pogos that go peek at through holes slightly higher that those that peek at SMD pads. That would have made the process of fitting the board much better.

Project info at EE & CS blog.