Sunday, May 13, 2012

Radioactive man? Milford resident pulled over by state police

Amanda Cuda
Updated 08:36 p.m., Thursday, May 10, 2012

Mike Apatow was minding his own business Wednesday, driving to an appointment for work in Washington Depot when a state police car appeared suddenly and signaled for the Milford resident to pull over.

Apatow, 42, was entering Interstate 84 in Newtown when the cruiser appeared, and he had no idea what he'd done to merit police attention. It turns out he didn't do anything.

But earlier that day, Apatow, who'd experienced a recent spike in his blood pressure, had a nuclear stress test at Cardiology Associates of Fairfield County in Trumbull. In the test, a small amount of a radioactive material is injected into the veins and used to help track blood flow to the heart.

Though the amount of radioactive material used in the test is relatively low -- equal to a few X-rays or a diagnostic CT scan -- it was enough to set off a radioactivity detector in the state police car. The detectors are used to help identify potential terror threats.

"I asked the officer `What seems to be the problem?' " Apatow said. "He said `You've been flagged as a radioactive car.' "

Apatow's doctor had given him a document attesting that he'd had a medical procedure involving a small amount of radioactive material that he handed to the officer. A Stratford firefighter, Apatow was more curious than annoyed by the incident.

"I had no idea the police even had devices like that," he said. "I imagined it being like a cartoon -- like I'm driving down the street and my car was glowing."

State Police spokesman Lt. J. Paul Vance confirmed that many of the state police cars have the radioactivity detectors. "It's part of our homeland security operations here," Vance said. "It's just another layer of public safety that we have in this state."

Though the goal of the detectors is to alert police to motorists who might be carrying hazardous materials, cases like Apatow's happen from time to time.

"They're very sensitive," Vance said of the detectors.

Apatow had the stress test after feeling ill while working at the Fire Department. He took his blood pressure and found it was 180 over 110 -- much higher than the 120 over 70 reading he usually gets. He attributed the spike to a variety of potential factors, including a lack of sleep. On Thursday, after visiting his doctors again, he was cleared for duty.

Dr. Gilead Lancaster, president of the Connecticut chapter of the American College of Cardiologists, said Apatow's experience with the stress test isn't as rare as some might think. Lancaster, also director of non-invasive cardiology at Bridgeport Hospital, said a colleague knew of an incident in which a patient was traveling by plane the day after a stress test and set off alarms in the airport. "It's definitely known that this happens, and we do let patients know that there is a chance that they could be picked up," he said.

He said patients are also often told to avoid close contact with family immediately following the stress test.

Apatow said his doctors told him not to go within 10 feet of his infant son within 24 hours of the test. Despite this, Lancaster said the amount of radioactive material used in the stress is unlikely to be harmful to the patient. "Any amount of radiation is harmful, but nobody has yet shown that this level of radiation has been of significant harm, especially to adults," he said.

Dr. Lawrence Schek, chief medical officer and chairman of cardiology at St. Vincent's Medical Center in Bridgeport, said facilities that perform these tests have to be certified and are meticulous about safety.

"There's very strict criteria in place," he said.

Wednesday, May 2, 2012

sigrok - cross-platform, open-source logic analyzer software with protocol decoder support

Wed, 2012-05-02 16:05 — Uwe Hermann


I'm happy to finally announce an open-source (GNU GPL), cross-platform (Linux, Mac OS X, FreeBSD, Windows, ...) logic analyzer software package myself and Bert Vermeulen have been working on for quite a long time now: sigrok (it groks your signals).

History

I originally started working on an open-source logic analyzer software named "flosslogic" in 2010, because I grew tired of almost all devices having a proprietary and Windows-only software, often with limited features, limited input/output file formats, limited usability, limited protocol decoder support, and so on. Thus, the goal was to write a portable, GPL'd, software that can talk to many different logic analyzers via modules/plugins, supports many input/output formats, and many different protocol decoders.

The advantage being, that every time we add a new driver for another logic analyzer it automatically supports all the input/output formats we already have, you can use all the protocol decoders we already wrote, etc. It also works the other way around: If someone writes a new protocol decoder or file format driver, it can automatically be used with any of the supported logic analyzers out of the box.

Turns out Bert Vermeulen had been working on a similar software for a while too (due to exactly the same reasons, crappy Windows software, etc.) so it was only logical that we joined forces and worked on this together. We kept Bert's name for the software package ("sigrok"), set up a SourceForge project, mailing lists, IRC channel, wiki, etc. and started working.

Overview, Features

You can get the lastest sigrok source code from our main git repository:
$ $ git clone git://sigrok.git.sourceforge.net/gitroot/sigrok/sigrok
Here's a short overview of sigrok and its features as of today. The software consists of the following components:

Tuesday, May 1, 2012

AE EP#33 Very Simple HV-genertation Jig

Posted on May 1, 2012 by Claudio
Ready for some Spitzensparken?


So currently I’m testing several different approaches on generating the HV for the scope project. This is my favourite for it’s simplicity. The schematic is Here:

Be sure to use a very good cap, that can widthstand the hight currents when discharging. The parts are not critical, any transistor, that can handle the power will do and the resistor values are just for orientation.

Have fun watching!


The whole arrangement will make a top voltage of about 400 V with two secodaries at 24 V, you can go muuuuuuuch higher with lower values and resistor values. In my very first tesla-coil almost the same arrangement makes somewhat 4 KV.

See you then!

Tuesday, April 24, 2012

Friday, April 13, 2012

Thursday, April 12, 2012

The Most Beautiful Homemade Device I’ve Ever Seen






I covered British electronics hobbyist Rupert Hirst’s lovely freeform headphone amp back in December, when it was still “just” a skeletonized circuit. Now he’s finished up by casting the meticulously-constructed electronics in clear resin, with equally meticulous care. He built a custom mold from 1.5mm cardstock, carefully sealed the jacks against resin infiltration, and mounted the wire frame inside the mold. After pouring the resin and allowing it to cure, he squared up the block on a belt sander, chamfered the edges with a router, and finally polished everything up with wet/dry sandpaper and Brasso. Rupert’s aesthetic—doing relatively simple things with extraordinary attention to detail—is always inspirational to me.

Crystal cMoy Freeform Headphone Amp

Wednesday, April 4, 2012

TCPIP and WIFI over a simple serial interface

April 4, 2012 in Chips by DP | comments


Sjaak tipped us to the MCW1001A, a TCP/IP stack and WiFi management IC with a simple serial interface. It stands between your project and a MRF24WB0MB WiFI module so you don’t have to mess with a full TCP/IP network implementation.
MCW1001A is a companion chip to the MRF24WB0 802.11 module. It provides simple socket based method of sending and receiving data from the MRF24WB0 802.11 module. The MCW1001A has an on-board TCP/IP stack and 802.11 connection manager to simplify the connection between a wireless network and the TCP/IP stack management. After the initial configuration is set, the MCW1001A can access the MRF24WB0 802.11 module to connect to a network and send/receive serial data over a simple UART interface from the Host controller.
Via the forum.

Saturday, March 31, 2012

Software-Defined Radio For $11


rtl-sdr

DVB-T sticks based on the Realtek RTL2832U can be used as a cheap SDR, since the chip allows transferring the raw I/Q samples to the host, which is officially used for DAB/DAB+/FM demodulation. The possibility of this has been discovered by the V4L/DVB kernel developer Antti Palosaari.

Specifications

The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s, however, the highest sample-rate without lost samples that has been tested so far is 2.8 MS/s. The frequency range is highly dependent of the used tuner, sticks that use the Elonics E4000 offer the best range (64 - 1700 MHz).

Supported Hardware

So far, the following devices are supported:
  • ezcap EzTV668 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner) (sources: AliExpress, Dealextreme)
  • ezcap EzTV666 USB 2.0 DVB-T/DAB/FM stick (Elonics E4000 tuner, picture)
  • Hama nano DVB-T stick (Elonics E4000 tuner)
  • Terratec NOXON DAB/DAB+ USB-Stick (Fitipower FC0013 tuner)

People over at reddit are collecting a list of other devices that are compatible.

Other sticks based on the RTL2832U might be added in the future as well.

This is the PCB of the ezcap-stick:


More pictures can be found here.

Software

rtl-sdr is a commandline tool that can initialize the RTL2832, tune to a given frequency, and record the I/Q-samples to a file.

The code can be checked out with: 
git clone git://git.osmocom.org/rtl-sdr.git
It can also be browsed on http://cgit.osmocom.org/cgit/rtl-sdr/

Progress
A GNU Radio source block is being created

Building the software

To build it, simply run 'make' in the src/-directory and make sure you have libusb1.0-0-dev installed.

Usage

Example: To tune to 392.0 MHz, and set the sample-rate to 1.8 MS/s, use: 
./rtl-sdr /tmp/out.bin -s 1800000 -f 392000000
If the device can't be opened, make sure you have the appropriate rights to access the device (udev-rules, or running it as root).

Known problems

If the samples are written to a harddrive, and not a ramdisk, samples may get dropped. An improved version with proper buffering and asynchronous usage of libusb is in the works.

Using the data

To convert the data to a standard cfile, following GNU Radio Block can be used:


The GNU Radio Companion flowgraph (rtl2832-cfile.grc) is attached to this page. It is based on the FM demodulation flowgraph posted by Alistair Buxton on this thread.

What has been successfully tested so far is the reception of TETRA, GMR and GSM.


Multiple GMR-carriers can be seen in a spectrum view with the full 3.2 MHz bandwidth (at 3.2 MS/s).

Monday, March 19, 2012

Microwave Oven Hacking 101 (and 102 and 103)




An anonymous tipster sent in these great videos: how to hack microwave oven transformers. The first video shows the complete disassembly of an oven using only a screwdriver, pliers, and hammer. Part two delves into the science of how the transformer works, while the third part shows how to wind your own. Parts two and three after the break.




Monday, March 12, 2012

Simple Circuit Turns PWM Into A Digitally Adjustable Precision Reference

Electronic Design
Date Posted: February 10, 2012 03:11 PM  
Author: Rick Mally
 
A shunt regulator acts as the feedback element in a low-pass Sallen-Key filter, converting a 5-V PWM signal to a dc value between –2.5 V and 2.5 V based on duty cycle.
Designs frequently require the conversion of a microprocessor’s pulse width modulation (PWM) signal into an analog voltage. Often a passive single-pole RC filter will satisfy design requirements, but this approach typically suffers from several drawbacks including slow response time, noisy results, and having an unbuffered output.

The circuit described here uses the ubiquitous LM431 shunt regulator to implement a second-order Sallen-Key low pass filter together with a level shifter (see the figure). Compared to the traditional approach, it provides a far sharper roll-off along with a low-impedance output, bipolar output. It will produce a –2.5- to +2.5-V output with a 0- to 5-V PWM signal input. The value of VOut is equal to (5 V × dc) – 2.5 V, where dc is the PWM duty from 0.0 to 1.0 (0% to 100%).

The component values depicted provide a flat response with a cutoff frequency around 2300 Hz, a –12-dB/octave roll-off, and drive capability of about 3 mA. You can easily change the cutoff frequency by adjusting R1 and R2 or C1 and C2, although it is important to keep R1 equal to R2 and C2 at about half the value of C1.

Doubling the resistor or capacitor values will cut the frequency in half. Halving either set of values will double the cutoff frequency. You can adjust R3 to provide more output current or to reduce power consumption. The 5-V rails depicted do not have to be precise and can be a higher voltage. Only the PWM input signal needs to be precisely 5 V.

Because it uses only six components, this circuit can be very cost effective. The LM431 can be purchased for as low as 10 cents in single-unit quantities, well below that of any op amp.

Editor’s Note: See Texas Instruments Application Report SLOA024B, “Analysis of the Sallen-Key Architecture,” for additional information on Sallen-Key filters.

Getting Started with CircuitLab

Sunday, March 11, 2012

XIG Update Pushes Wireless Data to Projects



I’m a big fan of the XBee Internet Gateway. I used it for The Networked On Air Light and a personal project called the Ego Ticker. XIG lets you use XBee radios to wirelessly connect your projects to the internet. Previously, your project would request a URL via serial to the XBee radio and the response (i.e. a webpage’s HTML) would be returned via serial. It works for a lot of different types of wireless projects, but it means that you sometimes have to poll for data, which you don’t always want to do. It’s like asking over and over again “are we there yet?” instead of saying “let me know when we get there.”

The latest version of XIG lets you communicate in both directions with your wireless project, meaning you can do away with the pesky polling. Check out the video above to get a quick demo of how to set up XIG push serial data to your project using the iDigi Cloud and also take a look at the project’s wiki to see a few other ways of communicating with your project from the cloud. According to Jordan Husney, iDigi Solutions Architect, the XIG creates a persistant outbound connection to the iDigi Cloud, so you won’t have to monkey around with your router’s settings to get data from the internet to your projects. I have a few projects in mind that this update is perfect for.

2011 DCC - Bluetooth for Microcontroller Circuits

Wednesday, March 7, 2012

Tool Review: Syringe Applicators for Plastic Solvent Cements



If you’ve worked with acrylic or certain other plastics before, you might be aware that they bond best with solvent-based adhesives. Solvent-based cements provide the least mess and cleanest bonds if applied with care, helping your projects and enclosures look even better.


Solvent cements are best applied via a capillary action, where you assemble the to-be-bonded plastic pieces and let small amounts of the liquid flow into the joint. There are two main types of applicators you can use – squeeze-bottles and syringes.

Going back more than a decade, I used to purchase my plastic materials and supplies over at Canal Street, in NYC. There were specialty plastics shops that had everything I needed, and Pearl Paint carried a few plastic-working tools and accessories as well. But a couple of years ago when I went back, I found higher prices and almost no selection.


Looking online, almost all online plastics suppliers do carry several sizes of syringes and applicator bottles, but their prices seem a bit steep, even with quantity discounts. Because of this I started ordering my applicator syringes from industrial suppliers. Syringes are quite easy to find, but blunted applicator needles can be a little harder to come by.


Sunday, March 4, 2012

Saturday, March 3, 2012

Tuesday, February 28, 2012

How-To: Splice Wire to NASA Standards

Some commenters on Friday’s post about using a washer as a soldering aid noticed my sloppy splicing technique and were kind enough to educate me about the so-called “Western Union splice,” aka the “Lineman’s splice,” which is the preferred method for twisting solid-core wire leads together for inline electrical connections.

Developed during the heydey of the telegraph, the Lineman’s splice is designed for connections that will be under tension. It is commonly claimed that, properly made, a Lineman’s splice is stronger than the wires of which it is composed. In any case, it is a time-proven method, and, coolest of all, one of NASA’s Required Workmanship Standards. To wit, in a NASA-approved Lineman’s splice:
  1. The conductors shall be pre-tinned.
  2. There shall be at least 3 turns around each conductor and the wraps shall be tight with no gaps between adjacent turns.
  3. The wraps shall not overlap and the ends of the wrap shall be trimmed flush prior to soldering to prevent protruding ends.
  4. Conductors shall not overlap the insulation of the other wire.
Though the Lineman’s splice was originally used without solder, today soldering is common. And NASA insists on it:
  1. Solder shall wet all elements of the connection.
  2. The solder shall fillet between connection elements over the complete periphery of the connection.
This material comes from page 84 of NASA-STD 8739.4, which is a great reference if you’re interested in best practices for interconnecting cables and wires. [Thanks, Alex Barclay!]


NASA TECHNICAL
STANDARD
NASA-STD 8739.4
with Change 6

National Aeronautics and Space Administration
Washington, DC 20546
Approved: 1998-02-09
Revalidation Date: 2008-07-25
Change 6 approved: 2011-03-29
View PDF