Electrical Engineering Crossword (Issue 280)

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



2.    DOPPLERLIMIT—Temperature restrictions for laser cooling techniques [two words]
4.    PINKNOISE—This signal sees the world through rose-colored glasses [two words]
5.    BOLTZMANNCONSTANT—k or kB [two words]
7.    XORGATE—A half adder is made of an AND gate and one of these [two words]
14.    NEPER—Symbolized by “Np”
15.    GOTOPAIR—Two tunnel diodes used in high-speed gate circuits [two words]
17.    YAGI—Unidirectional antenna
18.    PHOSPHOR—Used as a light source in a cathode ray tube
19.    KERREFFECT—All materials show this, but certain liquids display it more strongly than others [two words]


1.    WEINBRIDGEOSCILLATOR—This type generates sine waves [three words]
3.    INTEGRATEDINJECTIONLOGIC—These digital circuits are built with several collector BJTs [three words]
6.    CARBONNANOTUBES—Their electronic properties can be metallic or semiconducting [two words]
8.    GILBERTCIRCUIT—Uses diodes and transistors’ logarithmic properties to compensates for nonlinearities and instabilities [two words]
9.    ADDRESSINGMODE—Can be implied by the instruction’s function [two words]
10.    SINADRATIO—Used to measure a signal’s standards
11.    FLATPACK—Semiconductor network sealed in a thin rectangular package
12.    SPEECHCLIPPING—Process that limits peak signals [two words]
13.    COMPANDOR—Condenses or enlarges an electric signal’s dynamic range
15.    GLASS—Device under development by search engine giant
16.    LILLIPUTIAN—A very small robot


Electrical Engineering Crossword (Issue 279)

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



1.    ERASABLE—The second “E” in EEPROM
4.    NYCRESISTOR—Brooklyn, NY-based open-community workspace [two words]
5.    WHITEHAT—A hacker with ethics may don one of these [two words]
6.    WIMAX—aka, IEEE 802.16
8.    STRUCTUREDQUERY—A type of data-management language [two words]
9.    PACKETSWITCHING—Data grouping method [two words]
11.    VOLTOHMMETER—Capable of measuring  voltage, current, and resistance [three words]
12.    ELUA—It’s free, open source, and embedded
13.    BUCK—A switched-mode power supply converter
14.    GOODPUT—This can be calculated by dividing a transmitted file’s size by the amount of time it takes to transfer the file
16.    GRAYCODE—One bit makes a difference [two words]
17.    UBUNTU—Linux-based OS
18.    WEARLEVELING—When applied to a flash memory, this technique can level out the amount of writes to any given memory block across the entire memory chip [two words]
19.    MOODLE—E-learning software developed by Australian computer scientist Martin Dougiamas
20.    CROSSEDFIELD—This type of microwave amplifier can also be used as an oscillator [two words]


2.    LONGTERMEVOLUTION—Wireless communication standard [three words]
3.    CHEMILUMINESCENCE—A chemical reaction that creates a light emission
7.    BAXANDALL—A negative-feedback circuit used in high-quality audio amplifiers
15.    PAUSEUS—BASIC command that creates a microsecond-based delay


Solar Cells Explained (EE Tip #104)

All solar cells are made from at least two different materials, often in the form of two thin, adjacent layers. One of the materials must act as an electron donor under illumination, while the other material must act as an electron acceptor. If there is some sort of electron barrier between the two materials, the result is an electrical potential. If each of these materials is now provided with an electrode made from an electrically conductive material and the two electrodes are connected to an external load, the electrons will follow this path.

Source: Jens Nickels, Elektor, 070798-I, 6/2009

Source: Jens Nickels, Elektor, 070798-I, 6/2009

The most commonly used solar cells are made from thin wafers of polycrystalline silicon (polycrystalline cells have a typical “frosty” appearance after sawing and polishing). The silicon is very pure, but it contains an extremely small amount of boron as a dopant (an intentionally introduced impurity), and it has a thin surface layer doped with phosphorus. This creates a PN junction in the cell, exactly the same as in a diode. When the cell is exposed to light, electrons are released and holes (positive charge carriers) are generated. The holes can recombine with the electrons. The charge carriers are kept apart by the electrical field of the PN junction, which partially prevents the direct recombination of electrons and holes.

The electrical potential between the electrodes on the top and bottom of the cell is approximately 0.6 V. The maximum current (short-circuit current) is proportional to the surface area of the cell, the impinging light energy, and the efficiency. Higher voltages and currents are obtained by connecting cells in series to form strings and connecting these strings of cells in parallel to form modules.

The maximum efficiency achieved by polycrystalline cells is 17%, while monocrystalline cells can achieve up to 22%, although the overall efficiency is lower if the total module area is taken into account. On a sunny day in central Europe, the available solar energy is approximately 1000 W/m2, and around 150 W/m2 of this can be converted into electrical energy with currently available solar cells.

Source: Jens Nickels, Elektor, 070798-I, 6/2009

Source: Jens Nickels, Elektor, 070798-I, 6/2009

Cells made from selenium, gallium arsenide, or other compounds can achieve even higher efficiency, but they are more expensive and are only used in special applications, such as space travel. There are also other approaches that are aimed primarily at reducing costs instead of increasing efficiency. The objective of such approaches is to considerably reduce the amount of pure silicon that has to be used or eliminate its use entirely. One example is thin-film solar cells made from amorphous silicon, which have an efficiency of 8 to 10% and a good price/performance ratio. The silicon can be applied to a glass sheet or plastic film in the form of a thin layer. This thin-film technology is quite suitable for the production of robust, flexible modules, such as the examples described in this article.

Battery Charging

From an electrical viewpoint, an ideal solar cell consists of a pure current source in parallel with a diode (the outlined components in the accompanying schematic diagram). When the solar cell is illuminated, the typical U/I characteristic of the diode shifts downward (see the drawing, which also shows the opencircuit voltage UOC and the short-circuit current ISC). The panel supplies maximum power when the load corresponds to the points marked “MPP” (maximum power point) in the drawing. The power rating of a cell or panel specified by the manufacturer usually refers to operation at the MPP with a light intensity of 100,000 lux and a temperature of 25°C. The power decreases by approximately 0.2 to 0.5 %/°C as the temperature increases.

A battery can be charged directly from a panel without any problems if the open-circuit voltage of the panel is higher than the nominal voltage of the battery. No voltage divider is necessary, even if the battery voltage is only 3 V and the nominal voltage of the solar panel is 12 V. This is because a solar cell always acts as a current source instead of a voltage source.

If the battery is connected directly to the solar panel, a small leakage current will flow through the solar panel when it is not illuminated. The can be prevented by adding a blocking diode to the circuit (see the schematic). Many portable solar modules have a built-in blocking diode (check the manufacturer’s specifications).

This simple arrangement is adequate if the maximum current from the solar panel is less than the maximum allowable overcharging current of the battery. NiMH cells can be overcharged for up to 100 hours if the charging current (in A) is less than one-tenth of their rated capacity in Ah. This means that a panel with a rated current of 2 A can be connected directly to a 20-Ah battery without any problems. However, under these conditions the battery must be fully discharged by a load from time to time.

Practical Matters

When positioning a solar panel, you should ensure that no part of the panel is in the shade, as otherwise the voltage will decrease markedly, with a good chance that no current will flow into the connected battery.

Most modules have integrated bypass diodes connected in reverse parallel with the solar cells. These diodes prevent reverse polarization of any cells that are not exposed to sunlight, so the current from the other cells flows through the diodes, which can cause overheating and damage to the cells. To reduce costs, it is common practice to fit only one diode to a group of cells instead of providing a separate diode for each cell.

—Jens Nickels, Elektor, 070798-I, 6/2009

Electrical Engineering Crossword (Issue 278)

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


4.    ADIABATIC—Heat is neither gained nor lost
5.    DISCRETECIRCUIT—Made of resistors and transistors; not integrated [two words]
8.    FULLDUPLEX—Two-way communication [two words]
10.    KERMIT—Muppet-inspired protocol
12.    DEBIAN—Unix-like OS
14.    CHIRP—Conveys information
16.    FORTRAN—Others like it include BASIC and Pascal
18.    NANOKERNEL—Contains a minute amount of code capable of executing in the hardware’s privileged mode
19.    RHEOSTAT—Current regulator


1.    BIPOLARJUNCTION—There are two types: NPN and PNP [two words]
2.    ECBBUS—1970s communication system for Zilog and Intel microprocessors [two words]
3.    VISUALSERVOING—Used to control a robot’s motions [two words]
4.    ATTOSECOND—10-18 of a second
6.    NICKELCADMIUM—This small, light, high-power type is commonly used in hand-held devices [two words]
7.    DEFCON—Place where hackers annually assemble
9.    PIGGYBACKING—Bi-directional data transmission
11.    GRASSHOPPER—Programming language for rhinos
13.    FLOSSMANUALS—Netherlands-based foundation that provides information about and access to free software [two words]
15.    RASPBERRYPI—An inexpensive SBC [two words]
17.    LIDAR—Laser-based measurement technique


Electrical Engineering Crossword (Issue 277)

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


6.    ALGORITHM—Search engines use them to produce real-time results
9.    LOSSYCOMPRESSION—Condenses data by getting rid of some of it [two words]
11.    YOTTABYTE—Approximately 1,024 bytes
14.    PETAFLOP—Measures an FPU’s performance
15.    JQUERY—JavaScript library popularity contest winner
17.    THICKCLIENT—Able to function without a central server [two words]
18.    NYBBLE—4 bits
19.    DEGAUSSING—Gets rid of magnetism
20.    SPINTRONICS—aka, magnetoelectronics


1.    YANG—Co-founded a multinational Internet company in 1994
2.    MICROSOFT—Originally created and sold BASIC computer programs for the Altair 8800 microcomputer
3.    CHARACTERLARGEOBJECT—Used to store large amounts of text [three words]
4.    ACGENERATOR—Changes mechanical energy into electrical energy [two words]
5.    DROPPER—Installs malicious code onto computers
7.    TRINITRON—Sony Corp.’s CRT technology
8.    BEAMWIDTH—Commonly specified at –6 dB, –10 dB, and –20 dB
10.    OVERCLOCKING—Makes the time go by more quickly
12.    FERROMAGNETIC—e.g., iron, cobalt, and nickel
13.    BAUDOTCODE—An early digital communication method [two words]
16.    AUTODYNE—Invented in 1914 by electrical engineer Edwin Armstrong, who is also credited with creating FM radio transmission


Electrical Engineering Crossword (Issue 276)

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

3.    CRAY—Seattle, WA-based supercomputer company founded in the 1970s
5.    SUPERSTATE—A subprogram common to several states [two words]
7.    ONESCOMPLIANT—Inverted bits’ value [two words]
11.    BACKPLANE—Lacks processing and storage
13.    FALSECLOCK—Locks on an incorrect frequency [two words]
15.    TERNARY—This signal is capable of taking on one of three conditions
16.    BLUMLEIN—Known for advancements in telecommunications and radar
17.    JABBER—XML messaging protocol (hint: prior to 2000)
18.    DIRECTCURRENT—Zero frequency [two words]
20.    SERIALTRANSFER—Moves data bit by bit [two words]

1.    LYAPUNOV—Theory applies input-to-state (ISS) to systems with inputs
2.    LOWFREQUENCYOSCILLATOR—Produces a frequency below approximately 20 Hz [three words]
4.    HASHING—Security method
6.    SIGNIFICAND—aka, mantissa
8.    THYRISTOR—They have a four-layer N- and P-type construction
9.    HALFADDER—Combines two single binary digits [two words]
10.    DARKTRACE—A type of direct-view bistable storage tube [two words]
12.    FARADAYCAGE—Electric field-buffer [two words]
14.    SYMMETRIC—Uses the same key to code and decode
19.    KAHAN—Helped create the IEEE 754 floating-point computation specification

Electrical Engineer Crossword (Issue 275)

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


2.    UNIFIEDMODELING—Language that standardizes software specifications
3.    KELVINBRIDGE—Compares low resistance values [two words]
6.    THINCLIENT—A codependent program [two words]
10.    BANANAPLUG—Makes electrical connections [two words]
11.    CONDENSER—aka capacitor
13.    ASTABLE—A multivibrator circuit
15.    FLIPFLOP—A fundamental building block [two words]
18.    AMMETER—Used to calibrate current
19.    CLOCKGATING—Method of lowering dynamic power dissipation [two words]
20.    THERMIONICVALVE—Uses a vacuum to control electric current [two words]


1.    VISITORPATTERN—Keeps an algorithm away from an object structure
4.    RUNTIME—Multi-lingual computer system
5.    FIELDEFFECT—This type is unipolar [two words]
7.    LISSAJOUSCURVE—An oscilloscope trace [two words]
8.    NONMASKABLE—Cannot be ignored
9.    CASCODECIRCUIT—Provides amplification [two words]
12.    CRON—Keeps things on schedule
14.    ROENTGEN—Radiation measurement
16.    RETFIE—Instruction that enables new interrupts to occur
17.    SELSYN—aka mag-slip

Electrical Engineer Crossword (Issue 274)

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

1.            MOSIPROTOCOL—Adds a state indicating ownership [two words]

3.            SPECTROMETER—Measures wavelengths

8.            SHELL—Protects an operating system’s kernel

10.          CHARGE—Q

12.          ASSIGN—A FORTRAN control statement

13.          HALL—American physicist (1855–1938) who had an “effect” [two words]

15.          FIELDPROGRAMMABLE—Configurable after purchase [two words]

17.          MOUNTPOINT—In a Linux system, create this first to access the queue [two words]

19.          CORDIC—Calculate digit by digit

20.          MEISSNEREFFECT—Flux jumping [two words]



2.            INTERPROCESSCOMMUNICATION—Data exchanging method [two words]

4.            SQUIRRELCAGE—Commonly used in asynchronous motors [two words]

5.            DEGLITCHER—Type of delay circuit, serves as a pulse generator

6.            MERCURYARC—Emits  bright bluish-green light [two words]

7.            BALLGRIDARRAY—Packages ICs [three words]

9.            THREADEDCODE—A compiler technique [two words]

11.          DARAF—Unit of elastance

14.          AMPEREHOUR—3,600 coulombs [two words]

16.          RIPPLE—Unwanted undulation

18.          NIXIE—Used for numeric display


Electrical Engineer Crossword (Issue 273)

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


1.         BITDENSITY—Bits per inch of magnetic tape, for example [two words]

3.         KALMANFILTER—aka LQE [two words]

5.         EMBEDDEDSECURITY—Circuit Cellar columnist Patrick Schaumont covers this topic with articles about authentication, encryption, and electronic signatures [two words]

7.         HAMMING—Error-correcting code

8.         SPURIOUS—Unintentional

11.       LAND—Electronics and Computer Engineering professor at Cornell University and Circuit Cellar frequent contributor (many of his students contribute to Circuit Cellar as well)

13.       CLAPP—American inventor who developed an oscillator frequency standard

14.       ELECTRODE—Able to interact with nonmetallic circuit parts

16.       RINGOSCILLATOR—A feedback structure with an odd number of digital inverters [two words]

17.       PLESIOCHRONOUS—A system that’s not quite in synch

18.       OSCILLOGRAPH—Takes electric current measurements

19.       REFLECTEDBINARYCODE—Created by Bell Labs physicist and researcher Frank Gray [three words]



2.         DEADBAND—Potentiometer’s part shortened by a tap [two words]

4.         BECHTOLSHEIM—Electronics engineer and co-founder of the company that created Java

6.         CHIPBIOMETRICS—Digital fingerprints [two words]

9.         INCANDESCENT—Illuminating

10.       ALOHANET—Computer networking system from the 1970s

12.       EEVBLOG—Where to find electronics engineer David L. Jones’s off-the-cuff online videos

15.       EULERMETHOD—Solves equations [two words]

17.       POPOV—Helped make electromagnetic radio waves more useful

Electrical Engineer Crossword (Issue 272)

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


1.     JACOBSLADDER—Climbing arc [two words]

5.     WOZNIAK—Apple I

8.     SPARKCOIL—Uses a low-voltage DC supply to create high-voltage pulses

10.   JITTER—Creates an imperfect timing signal

11.   ERG—Energy measurement

13.   ACOUSTICOHM—Equivalent to µbar s/cm3 [two words]

15.   BUFFER—Provides electrical isolation

16.   WIFI—Provides movement to smartphones, PCs, and tablets

17.   POSIX—An IEEE operating system compatibility standard

18.   PEAKTOPEAK—Alterations between high and low values

19.   MUTEX—Capable of ensuring atomic access to any shared resource

20.   NAKAMURA—University of California, Santa Barbara professor credited with inventing the blue LED



2.     OSCILLATOR—American physicist George W. Pierce (1872–1956); piezoelectric

3.     EIGENTONE—A pitch capable of resonance

4.     FRETSONFIRE—Open-source gameplay for music lovers [three words]

6.     NEGATIVEFEEDBACK—Type of amplifier invented in 1927 by Harold Black [two words]

7.     BAFFLE—Sound wave obstruction

9.     MORSECODE—A pre-texting means of communication [two words]

12.   COMBFILTER—Capable of causing delay [two words]

14.   CHIPSET—Intel created the first family of these

Electrical Engineer Crossword (Issue 271)

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


3.            CONFORMALCOATING—Used on PCBs intended for extreme environments [two words]

4.            LOOP—An often repetitious code sequence

7.            VUMETER—Measures program volume [two words]

8.            GALVANOMETER—An electric current identifier

10.         FACTORIAL—“n!”

11.         DIPMETER—Evaluates radio frequency circuits [two words]

13.         REEDSOLOMON—Non-binary code [two words]

16.         SHOCKLEY—One of a group of three co-inventors who, in 1956, were awarded the Nobel Prize in Physics for creating the transistor

18.         SUBSTRATE—An insulating board’s surface

19.         TELEPHONY—Concept proposed by Belgian engineer Charles Bourseul in 1856

20.         ACTUATOR—Electric motors and loudspeakers, for example



1.            TORODIAL—A type of inductor or transformer whose windings form a closed circular tube

2.            POTENTIOMETER—May be used to control volume on audio equipment

5.            PIEZOELECTRICITY—Often used to produce and detect high voltages, sound, and electronic frequency generation

6.            OCCAMPROCESS—An electronic circuit board manufacturing method [two words]

9.            FLYWHEEL—An energy-storing device

12.         MONOBLOCK—A single-channel power amp with high current power

14.         RELIABILITY—Quality over time

15.         MICROMETER—Used to measure small objects’ thickness

17.         EISLER—Austrian engineer (1907–992) credited with inventing the printed circuit

Electrical Engineer Crossword (Issue 270)

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


1.     ICONOSCOPE—The first widely used television camera tube

5.     INTERRUPTROUTINE—Responds to disturbances [two words]

8.     RADIXPOINT—Separates a number’s integer part from its fraction part [two words]

11.   IMPEDANCE—Bridge circuit used to measure resistance

14.   SALLENKEY—A simple filter topology used to implement second-order active filters [two words]

16.   TYNDALLEFFECT—Light scattering [two words]

17.   LADDER—A kind of passive filter

18.   INPUTOUTPUT—Microcontrollers contain these type of peripherals [two words]

19.   IDEMPOTENTLAW—The result never changes [two words]



2.     NANDCIRCUIT—Combines two types of functions in a binary circuit with two or more inputs and one output [two words]

3.     BARDEEN—Won the Nobel Prize in Physics twice

4.     DIODE—Developed in 1904 by English engineer John Ambrose Fleming

6.     ECHOBOX—A device that receives part of a transmitted pulse and transmits it back to the receiver [two words]

7.     KARNAUGHMAP—Used to simplify algebra expressions [two words]

9.     FARADY—English scientist (1791–1867) who published the law of induction

10.   GANGED—Tuning that uses a single control to tune two or more circuits

12.   DCGENERATOR—French instrument maker Hippolyte Pixii developed a prototype for this in 1832 [two words]

13.   ILLUMINATE—What an LED does

14.   SAWTOOTH—A waveform with a slow linear rise time and a fast fall time

15.   RCSERVO—An absolute-positioning actuator that is typically limited to a 180° rotation  [two words]