The answers for the crossword puzzle published in Circuit Cellar 259 (February 2012).
Tag Archives: CC259
RFI Bypasssing
With GPS technology and audio radio interfaces on his personal fleet of bikes, Circuit Cellar columnist Ed Nisley’s family can communicate to each other while sending GPS location data via an automatic packet reporting system (APRS) network. In his February 2012 article, Ed describes a project for which he used a KG-UV3D radio interface rigged with SMD capacitors to suppress RF energy. He covers topics such as test-fixture measurements on isolated capacitors and bypassing beyond VHF.
Photo 2 from the Febuary article, "RFI Bypassing (Part 1)." A pair of axial-lead resistors isolate the tracking generator and spectrum analyzer from the components under test. The 47-Ω SMD resistor, standing upright just to the right of the resistor lead junction, forms an almost perfect terminator. (Source: Ed Nisley CC259)
Ed writes:
Repeatable and dependable measurements require a solid test fixture. Although the collection of parts in Photo 2 may look like a kludge, it’s an exemplar of the “ugly construction” technique that’s actually a good way to build RF circuits. “Some Thoughts on Breadboarding,” by Wes Hayword, W7ZOI, gives details and suggestions for constructing RF projects above a solid printed circuit board (PCB) ground plane.
You can read this article now in Circuit Cellar 259. If you aren’t a subscriber, you can purchase a copy of the issue here.
Lacoste’s High-Speed ADC Discussion
High-speed analog-to-digital converters can be tricky—and sometimes costly—to work with. In his Circuit Cellar 259 article, “Playing with High-Speed ADCs,” columnist Robert Lacoste provided handy tips on effectively implementing them to your advantage. He used an Analog Devices AD9265-125 as an example.
A high-speed ADC is just a part of a high-performance digitizing system.
In response to the article, a reader wrote:
“Hello, Robert. Thanks for all the articles in CC. Your High Speed ADC covered some of the concepts I have been thinking about with creating a laser range finder using Pulsed time of flight. The problem is the frequencies are in the 20 GHz for 8-mm resolution. The ADC can be very low resolution, but the sampling has to be in the 40-GHz range. The sensors need to be dark 50% of the time to get even 10-GHz response times from the crystals. So, I was wondering how do the small handheld range finders work? They are accurate to 8 mm and cost $150+. Is there a easier way to do Time of Flight? Do you know how they do this? The internet is kind of a endless trail with nothing that leads to IC’s or circuits.”
Robert provided an insightful answer:
“The short and honest answer would be ‘I don’t know,’ as I’ve never worked or inspected the internals of a laser range finder. However I’m sure that they don’t use 20Gsps+ ADC’s… I would guess that they use more some kind of time interval to voltage converters, followed by a slow but high resolution ADC. The idea is basically to charge a capacitor between the transmit and receive pulses, and to measure to voltage on the capacitor. This technique is for example used in all Agilent’s period/frequency meters: these devices measure single-shot events with a resolution down to 10ps or so, and don’t include anything faster than a 100MHz clock. Look for ‘dual Vernier interpolation’ techniques. On the laser range side, I dug a little on the net and found this link which seems to confirm this assumption: http://herkules.oulu.fi/isbn9514269667/html/c305.html. There is at least one company who develops custom chips adequate for this job: http://www.acam.de/index.php?id=149. See there: www.acam.de/products/time-to-digital-converters/applications/laser-distance-meters/.”
You can purchase the issue in which this article appears in the CC Webshop.
Issue 259: Innovation in Wireless Technology
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Clayton Gumbrell's mbed-based QRSS-Rx
The topic of wireless communication is more relevant than ever. The technology is used everywhere from vehicles to hospitals to consumer electronics to military systems. Therefore, electronics engineers around the world are devoting their careers to innovating technologies to meet the ever-growing demand for wireless devices.
Since its inception in 1988, this magazine has been publishing articles on wireless technology. Examples include Ed Nisley’s “Digitizing Infrared Signals” (Circuit Cellar 2), Maurizio Ferrari’s “Secrets of Using the DS1209 in an RF Transponder” (Circuit Cellar 41), and Steve Ciarcia’s “Wireless Remote Control of the AVMux” (Circuit Cellar 46). This month we continue the tradition.
On page 14, Clayton Gumbrell describes his QRSS-Rx design. The mbed-based receiver can digitize a small bandwidth of RF signals and send them to a server for processing.
Turn to page 30 to learn how Steve Lubbers built his “KartTracker,” which is a standalone GPS-based timing system used to time racing activities. An LCD operates as a user interface, an integrated accelerometer records G forces, a serial port provides connections to a GPS receiver and a wireless transmitter, and removable flash memory stores data.
Ed Nisley tackles the topics of capacitor self-resonance, GPS technology, RF energy, and data transmission in the first part of his series titled “RFI Bypassing” (p. 38). He presents a radio project featuring SMD capacitors for suppressing RF energy, and he describes test-fixture measurements on isolated capacitors.
As usual, this issue is not devoted solely to its theme. CPUs, power supplies, ADCs, Linux, and protocols are also covered.
On page 24, Alexander Pozhitkov begins a two-part series about the NakedCPU platform. It is designed to provide full access to hardware and a CPU without any OS restrictions while working in the protected mode.
In the first part of his series on building a robust power supply, George Novacek described how to make a power supply operate properly when the primary power distribution bus voltage is lower than nominal. This month he explains what happens when it encounters an abnormal surge voltage (p. 44).
On page 52, Robert Lacoste details how to work with high-speed ADCs. The article is intended to demystify the process of using high-speed converters effectively.
Another topic that needs demystification is embedded Linux, which is why Bob Japenga has been covering the subject in his ongoing series “Getting Started with Embedded Linux.” This month he addresses various licensing issues you’ll face as you work with Linux (p. 60).
Columnist Jeff Bachiochi wraps up this issue with the article “Multi-Serial Protocol Tool” (p. 64). As you’ll see, it’s fairly easy to build a multi-serial protocol tool designed to connect from a USB host an I2C, SPI, RS-232/422/485, or Dallas 1-Wire format.
Issue 259: An Interview with Chris Gammell
In Circuit Cellar February 2012 (Issue 259), we feature a recent interview with Chris Gammell, the multitalented engineer who co-hosts The Amp Hour with Dave Jones. Chris tells us about his designs, workspace, podcasts, and much more. Here’s an excerpt:
NAN: What was the impetus for starting your radio show, The Amp Hour (www.theamphour.com) which you co-host with Dave Jones of the EEVblog?
CHRIS: I’m a member of the online community reddit, and actually an administrator of the ECE sub-group (http://reddit.com/r/ECE). Two years ago, there was a request on the site for podcasts and blogs featuring electronics, because the submitter wanted to learn more while in the car and on their bike. I tried a podcast by myself and it was dreadful. But once I posted it, Dave Jones happened to hear it and suggested we give it a shot together. We didn’t have much of a plan at first, just to get on the line and shoot the breeze for an hour or so. After the first two episodes, we began soliciting our listeners and Dave’s regular viewers for a name for the show. One of our listeners suggested “The Amp Hour” and it’s been roughly an hour-long show every week since. It’s one of my favorite times of the week and I’m so glad I have been able to continue doing the show, 70-some episodes later. If your readers haven’t had a chance to listen, I hope they will at some point in the future. I personally think the best time to listen to the show is on the way to or from work, or while sitting at your bench soldering.
NAN: Some recent Amp Hour interviewees included: Jeff Keyzer of the blog MightyOhm.com (December 2011); John Edmond, co-founder and director of Advanced Optoelectronics Technology at Cree (November 2011); and Joe Grand, president of Grand Idea Studio and a former member of the legendary hacker collective L0pht Heavy Industries (September 2011). How do you decide who to feature on the show? Can you tell us who has been your favorite or most memorable guest?
CHRIS: Your embedded programming readers out there undoubtedly know Jack Ganssle, who was a guest on our show. It was a ton of fun trading stories with him and hearing how the computer industry used to be driven by the demands of the… ahem…online adult industry. But really, all of our guests have been amazing. We choose guests who not only have interesting stories and work but also can chat about the weekly news and who enjoy electronics. I’m sure a couple of members of the Circuit Cellar audience will be in our sights as potential guests in the future!
To read the entire article, go to CC-Access.