Electronics Engineering Crossword (Issue 267)

The answers to Circuit Cellar’s October electronics engineering crossword puzzle are now available.


1.     QUADRATURESIGNAL—Can be produced using two sensors spaced at odd half-slot multiples around a single track [two words]

4.     MICROELECTROMECHANICAL—This type of system’s size ranges from 20 µm to 1 mm

8.     MANCHESTERCODE—A low-to-high transition means “0″ and a high-to-low transition means “1″ [two words]

9.     ABSOLUTEDECODER—Because these devices have only one track per bit of resolution, they can require large diameters, which gives them a nonvolatile and unique output for each position [two words]

15.   BATTERY—Italian physicist Alessandro Volta (1745–1827) is credited with inventing the first one of these in the 1800s

16.   DIGITALFILTER—A piece of software, firmware, or logic circuit that takes a digital data flow as an input and provides a filtered version of this signal on its output [two words]

17.   CONCURRENCY—Topic of columnist Bob Japenga’s ongoing article series, which began in Circuit Cellar 263, 2012

18.   EXBIBYTE—1,152,921,504,606,846,976 bytes

19.   RELATIVEHUMIDITY—Amount of water vapor in the atmosphere expressed as a percentage of the total amount the air can hold at the current temperature [two words]


2.     ACCELEROMETER—The design in Mark Pedley’s article, “eCompass: Build and Calibrate a Tilt-Compensating Electronic Compass” (Circuit Cellar 265, 2012), was built using one of these

3.     SANDER—New Zealand-based Circuit Cellar contributor and recent interviewee who is fascinated with advanced robot technologies

5.     PHASELOCKEDLOOP—This control system generateS an output frequency, which can be either higher or lower than the input, based on a reference input clock [three words]

6.     NEUROMORPHICCircuit Cellar’s October’s interviewee, Helen Li, believes this type of computing will solve the contradiction between the limited functions of computing systems and the ever-increasing variety of applications

7.     ELECTROSTATIC—This type of cell consists of a thin plastic film sandwiched between two metal stators

10.   BOOSTCONVERTER—Its output voltage is greater than its input voltage [two words]

11.   ARMSTRONG—American engineer (1890—1954) who invented the regenerative circuit, the super-regenerative circuit, the superheterodyne receiver, and modern frequency modulation (FM) radio transmission

12.   INCLINOMETER—Used to measure tilt

13.   SHALLENBERGER—American engineer (1860–1898) who invented an induction meter to measure alternating current

14.   MEMRISTOR—The functional equivalent of a synapse


Electronics Engineering Crossword (Issue 266)

The answers to Circuit Cellar’s September electronics engineering crossword puzzle are now available.


3.     ZUSE—German engineer inventor and engineer (1910–1995) who is credited with creating the Z3, a program-controlled Turing-complete computer

5.     ROOTMEANSQUARE—Alternating voltage/current with the exact same energy content as the same value of direct current; a.k.a., quadric mean [three words]

10.   BLOB—Stores binary data; synonym: drop

13.   KLYSTRON—A specialized linear-beam vacuum tube

16.   ELECTROMAGNET—English physicist and inventor William Sturgeon (1783-1850) is credited with using electric current to develop the first one of these objects in 1825

17.   LACOSTE—Circuit Cellar columnist who frequently writes about frequency

18.   SMARTSWITCH—An energy-saving device that was the topic of Fergus Dixon’s article (Circuit Cellar, 263 2012) [two words]

19.   PICOAMMETER—Measures low current


1.     PUBLICKEYCRYPTOGRAPHY—Decodes using two pieces of information, one public and one private [three words]

2.     COMPRESSIONDRIVER—A loudspeaker that achieves high efficiencies by using a consolidating technique [two words]

4.     SPIDER—The flexible collar that helps keep a voice coil magnetically centered

6.     MICROPOWERIMPULSERADAR—A pocket-sized radar that runs off AA batteries and is often used as a basic motion sensor for security applications [three words]

7.     ALPHATESTING—Check performed by an independent team on a system installed at a place other than the targeted customer’s site [two words]

8.     ATOMICOPERATION—An action that is non-interruptible by any other one and never presents partial results to an outside observer [two words]

9.     EMBEDDED—As Circuit Cellar prepares to celebrate its 25th anniversary, a  past, present, and future key theme of the magazine centers on this type of technology

11.   SIGNALPROCESSING—Involves measuring physical quantities with time and spatial variances [two words]

12.   FLOWCHARTING—Jeff Bachiochi describes how to use this technique to write code in this issue

14.   CONVOLUTION—Mark Csele’s article, “DSP-Based Color Organ” (Circuit Cellar, 249 2012), used this technique to create high-performance filters

15.   MULTIPLEXER—A device that combines input signals, shares a single transmission channel, and enables data compression


MCU-Based Prosthetic Arm with Kinect

James Kim—a biomedical student at Ryerson University in Toronto, Canada—recently submitted an update on the status of an interesting prosthetic arm design project. The design features a Freescale 9S12 microcontroller and a Microsoft Kinect, which tracks arm movements that are then reproduced on the prosthetic arm.

He also submitted a block diagram.

Overview of the prosthetic arm system (Source: J. Kim)

Kim explains:

The 9S12 microcontroller board we use is Arduino form-factor compatible and was coded in C using Codewarrior.  The Kinect was coded in C# using Visual Studio using the latest version of Microsoft Kinect SDK 1.5.  In the article, I plan to discuss how the microcontroller was set up to do deterministic control of the motors (including the timer setup and the PID code used), how the control was implemented to compensate for gravitational effects on the arm, and how we interfaced the microcontroller to the PC.  This last part will involve a discussion of data logging as well as interfacing with the Kinect.

The Kinect tracks a user’s movement and the prosthetic arm replicates it. (Source: J. Kim, YouTube)

The system includes:

Circuit Cellar intends to publish an article about the project in an upcoming issue.

Issue 268: EQ Answers

Problem 1: A transformer’s windings, when measured individually (all other windings disconnected), have a certain amount of inductance. If you have a 1:1 transformer (both windings have the same inductance) and connect the windings in series, what value of inductance do you get?

Answer 1: Assuming you connect the windings in-phase, you’ll have double the number of turns, so the resulting inductance will be about four times the inductance of one winding alone.

If you hook them up out of phase, the inductance will cancel out and you’ll be left with the resistance of the wire and a lot of parasitic inter-winding capacitance.

Problem 2: If you connect the windings in parallel, what value of inductance do you get?

Answer 2: With the two windings connected in-phase and in parallel, the inductance will be exactly the same as the single-winding case. But the resulting inductor will be able to handle twice the current, as long as the core itself doesn’t saturate.

Question 3: Suppose you have a 32-bit word in your microprocessor, and you want to count how many contiguous strings ones that appear in it. For example, the word “01110001000111101100011100011111″ contains six such strings. Can you come up with an algorithm that uses simple shifts, bitwise logical and arithmetic operators, but —here’s the twist—does not require iterating over each bit in the word?

Answer 3: Here’s a solution that iterates over the number of strings, rather than the number of bits in the word.

int nstrings (unsigned long int x)
   int result = 0;

   /* convert x into a word that has a '1' for every
    * transition from 0 to 1 or 1 to 0 in the original
    * word.
   x ^= (x << 1);

   /* every pair of ones in the new word represents
    * a string of ones in the original word. Remove
    * them two at a time and keep count.
   while (x) {
     /* remove the lowest set bit from x; this
      * represents the start of a string of ones.
     x &= ~(x & -x);

     /* remove the next set bit from x; this
      * represents the end of that string of ones.
     x &= ~(x & -x);
   return result;

Problem 4: For the purpose of timing analysis, the operating conditions of an FPGA are sometimes known as “PVT,” which stands for “process, voltage, and temperature.” Voltage and temperature are pretty much self-explanatory, but what does process mean in this context?

Answer 4: The term process in this case refers to the manufacturing process at the plant where they make the FPGA. It’s a measure of the statistical variability of the physical characteristics from chip to chip as they come off the line.
This includes everything from mask alignment to etching times to doping levels. These things affect electrical parameters such as sheet and contact resistance, actual transistor gains, and thresholds and parasitic capacitances.
These kinds of variations are unavoidable, and the P in PVT is an attempt to account for their effects in the timing analysis. The idea is to make the analysis conservative enough so that your design will work reliably despite these variations.

Contributed by David Tweed