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Reader I/O
Circuit Cellar has always invited readers to send in their comments about the magazine, the Web site, current contests, or whatever it is we're doing at the time. Rather than have the Reader I/O page in the print magazine, we've moved that feature to our Web site in order to expedite the posting process. We hope you'll stop by to drop off your comments, see what other readers are saying, or get any updated Editor's Notes that may pertain to articles in past issues.
CORRECTION
May 26, 2009
In Tom Cantrell’s article “Easy (E)mbed” (Circuit Cellar Issue 227, June 2009), the NXP part number should be “LPC236x” (not LPC263x) . The editorial department apologizes for the confusion. (Click here for an updated version of the article that reflects the proper part numbers.)
NOTE
March 6, 2009
Circuit Cellar thanks Smart Robots Inc. for the SR4 robot image that appears on the cover of Issue 224 (March 2009).
CORRECTIONS
February 2, 2009
The following changes/comments apply to Robert Lacoste’s article, “Microstrip Techniques” (Circuit Cellar Issue 223, February 2009).
A reader pointed out that the following sentence may be misunderstood: “the power transfer between a source and receiver is maximized when impedances are matched.”
Robert Lacoste replied:
“If you have a 50-ohm source, then the power delivered to the load will be maximized with a 50-ohm load as explained in the article. However, if you have a 50-ohm load and are allowed to choose any source impedance, then the power delivered to the load will be maximized with a 0-ohm source impedance, simply because the voltage on the load terminals will be higher. Unfortunately, in the RF world, if you match a 1-ohm source with a 50-ohm load, you may have other significant issues as 92% of the energy will be reflected back to the source, giving nasty mixing effects in the source if it is an active component.”
January 12, 2009
The following changes/comments apply to Robert Lacoste’s article, “PID Control Without Math” (Circuit Cellar Issue 221, December 221).
1. At the top of page 60, the article reads: “At equilibrium, the heat loss to the ambient air is exactly equal to the 3°C error multiply by Kd.” This is a typo. It should read “Kp,” not “Kd.”
2. A reader wrote: “The article uses Error = actual - target equation, but this seems to be opposite to the simulator code downloaded. Am I right that what appears in the article is just a typo?”
Robert Lacoste replied: “In fact, the sign of the command is just a convention. For example, if the controlled system is a motor-driven car, and if the sensor is a position sensor, then you could either need to send a positive or negative command to the motor for a positive error, depending on the wiring. Effectively, with the example the command (heating power) must be positive if the target is above the current temperature, so Error = target - actual with Kp > 0. But you could also have the opposite ...”
July 11, 2008
A mistake was found in Figure 1 in Robert Papp’s article, “Sound Effects Processing” (page 71, Circuit Cellar 216, July 2008). The corrected section of the schematic is now available at:
ftp://ftp.circuitcellar.com/pub/Circuit_Cellar/2008/216/Papp214Fig1b_corrected.pdf
April 22 , 2008
Regarding R7/R8 in Robert Lacoste’s April 2008 column, “Low-Power Techniques” (Circuit Cellar 213), note that R7 impact is probably very small as polarized only when the button is pushed. But R8 impact is not minor at all: 2 V/10 kohm = 200 microAmp. So, R8 must be far higher, 1 Mohm or so.
April 1 , 2008
In Tom Cantrell’s April column “More Than A Core” (Issue 213, p. 86), it was stated that the STM32 Primer uses an ARM7 MCU to provide a USB debug interface, but the part used is actually an 8-bit ST72651 MCU.
January 30 , 2008
Please note the following correction to Aubrey Kagan’s article, “Resilience in Embedded Designs (Part 3),” which ran in Issue 208 (November 2007). In Figure 2 on page 59, the decision box in the background routing the test is:
If cOldCheck0=cCheck0
The marked branch should be "Y" and not "N."
November 21 , 2007
In Figure 6 in Robert Lacoste’s issue 209 (December) article, an arrow is missing from "Output frequency" to the "Divide by N" block.
August 16 , 2007
In Robert Lacoste’s "Let's play with EMI" column published in issue 205 (August), he stated on page 67 that an FFT spectrum analyzer based on a 8-bit digitizer could provide a dynamic range of 48 dB. This is true if the signal is a pure sine, as when the signal amplitude will be lower than one LSB, the output of the ADC will be zero. However, as a reader pointed out, this is very pessimistic in real life. If you analyze a very small amplitude signal summed with some white noise, then the FFT calculation can bring signals out of the noise even if their amplitude is far below one LSB. This is due to the fact that the noise is "shared" between all FFT frequency bins, so each time you double the FFT size, the noise floor is lowered by 3 dB. And luckily noise is eveywhere.
January 3, 2007
During the final proofing stage of the editorial process, the editorial staff inadvertently inserted three typos into Tom Cantrell’s January 2007 article, “Hot Chips 18” (Circuit Cellar 198). Please note the following corrections:
Page 78, column 2, paragraph 3: “10 Kbps” should be “10 KBps”
Page 78, column 3, paragraph 1: “12.5 Mbps versus 10 Kbps” should be “12.5 MBps versus 10 KBps”
Editor’s note: According to IBM, the RAMAC transfer rate was “8.8 Kbytes/s” (http://www.research.ibm.com/journal/rd/255/ibmrd2505ZC.pdf).
Page 83, Table 2: "Xilinx Vertex-4" should be "Xilinx Virtex-4.
Our apologies go out to our readers and Tom Cantrell.
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