I’m adding definitions to this page on a continual basis. Entries without definitions are are entries that I haven’t had the time to work on yet.


555 timer IC — “The 555 timer IC is an integrated circuit used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two (556) or four (558) timing circuits in one package.”[WIKI]

ADCAnalog-to-Digital [A/D] Converter. “A converter that uniquely represents all analog input values within a specified total input range by a limited number of digital output codes, each of which exclusively represents a fractional part of the total analog input range. NOTE: This quantization procedure introduces inherent errors of ±1/2 LSB (least significant bit) in the representation because, within this fractional range, only one analog value can be represented free of error by a single digital output code.”[JEDEC]

ALUArithmetic Logic Unit.

anode — “(1) The p‑type region from which the forward current flows within a semiconductor diode. NOTE: In Schottky diodes, usually the barrier metal replaces the p‑type semiconductor region and the remaining semiconductor region is n‑type; however, some Schottky diodes have been made with the barrier metal replacing the n‑type semiconductor region, in which case the remaining semiconductor region is p‑type. (2) A circuit element to which positive bias is applied.”[JEDEC]

API — Application Programming Interface. A set of subroutine definitions, protocols, and tools for building application software. In general terms, it is a set of clearly defined methods of communication between various software components.

Arduino — “Arduino is an open-source electronics platform based on easy-to-use hardware and software. It’s intended for anyone making interactive projects.”[ARD]

Arduino Software (IDE) — There are two versions of the Arduino IDE: the online IDE (Arduino Web Editor) and the desktop IDE.

AVR — AVR is a family of 8-bit RISC single-chip microcontrollers developed by Atmel. Atmel says that the name AVR is not an acronym and does not stand for anything in particular. AVR microcontrollers are commonly found in embedded systems. They are also used in the Arduino line of open source board designs.

baud rate — Baud rate (a.k.a. modulation rate or symbol rate) is the number of symbol changes, waveform changes, or signaling events, across the transmission medium per time unit using a digitally modulated signal or a line code. The symbol rate is measured in baud (Bd) or symbols per second. In the case of a line code, the symbol rate is the pulse rate in pulses per second. Each symbol can represent or convey one or several bits of data. The symbol rate is related to the gross bitrate expressed in bits per second.

BJTBipolar Junction Transistor.




CMOSComplementary Metal–Oxide–Semiconductor. A technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits. CMOS technology is also used for several analog circuits such as image sensors (CMOS sensor), data converters, and highly integrated transceivers for many types of communication. Two important characteristics of CMOS devices are high noise immunity and low static power consumption.

data sheet —

decade — A range of electrical resistances, frequencies, or other quantities spanning from one to ten times a base value.


DIP — Dual In-line Package. a type of integrated circuit packaging. A DIP switch, for example, is an electric switch in a dual in-line package. In Catalan mythology, Dip is an evil demonic dog that drinks people’s blood.

DuPont wire — A jumper wire or group of wires in a cable—named for DuPont, one manufacturer of them—with a connector or pin at each end. They are used to interconnect the components of a breadboard or other prototype or test circuit, internally or with other equipment or components, without soldering.

EEPROMElectrically Erasable Programmable Read-Only Memory. “A reprogrammable read-only memory in which the cells at each address can be erased electrically and reprogrammed electrically.”[JEDEC]

EPROMErasable Programmable Read-Only Memory. “A reprogrammable read-only memory in which all cells can be simultaneously erased using ultraviolet light, after which the cells at each address can be reprogrammed electrically.”[JEDEC]

ESD — Electrostatic Discharge.

firmware —

flash memory —

GPIO — General-Purpose Input/Output. A GPIO is a generic pin on an integrated circuit or computer board whose behavior—including whether it is an input or output pin—is controllable by the user at run time. GPIO pins have no predefined purpose, and go unused by default.

I2C, I2C — Inter-Integrated Circuit. Pronounced I-squared-C, I2C is a multi-master, multi-slave, packet switched, single-ended, serial computer bus. It is widely used for attaching lower-speed peripheral integrated circuits to processors and microcontrollers in short-distance, intra-board communication.

IC — Integrated Circuit. “A circuit in which all or some of the circuit elements are inseparably associated and electrically interconnected so that it is considered to be indivisible for the purposes of construction and commerce.”[JEDEC]


IDE — Integrated Development Environment. An integrated development environment is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of a source code editor, build automation tools, and a debugger.

LCD — Liquid-Crystal Display.

LED — Light-Emitting Diode.

LSBLeast-Significant Bit.


Manchester modulation —


MOSFET — Metal-Oxide-Semiconductor Field-Effect Transistor.

n-type —

Bipolar Junction Transistor NPN Symbol

NPN — A mnemonic device for the NPN transistor symbol is “Not Pointing iN”, based on the arrows in the symbol and the letters in the name.

On-chip ISP Flash —

p-type —

PCB — Printed Circuit Board. A PCB “mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.”[WIKI]

Bipolar Junction Transistor PNP Symbol

PNP — A mnemonic device for the PNP transistor symbol is “Pointing iN Proudly” or “Pointing iN Permanently”, based on the arrows in the symbol and the letters in the name.

PSoC — Programmable System-on-Chip. A family of microcontroller integrated circuits by Cypress Semiconductor. These chips include a CPU core and mixed-signal arrays of configurable integrated analog and digital peripherals.

pull-down resistor

pull-up resistor —

PWM — Pulse-Width Modulation.

RC servo — Radio Control servo.

RF — Radio Frequency.

RFID — Radio-Frequency Identification.


RoHS — Restriction of Hazardous Substances Directive. “The Restriction of Hazardous Substances Directive 2002/95/EC, (RoHS 1), short for Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, was adopted in February 2003 by the European Union. The RoHS 1 directive took effect on 1 July 2006, and is required to be enforced and became a law in each member state. This directive restricts (with exceptions) the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment. It is closely linked with the Waste Electrical and Electronic Equipment Directive (WEEE) 2002/96/EC which sets collection, recycling and recovery targets for electrical goods and is part of a legislative initiative to solve the problem of huge amounts of toxic electronic waste. In speech, RoHS is often spelled out, or pronounced /rɒs/, /rɒʃ/, /roʊz/, or /ˈroʊhɒz/, and refers to the EU standard, unless otherwise qualified.”[WIKIROHS]

RPD — Pull-Down Resistor.

RPU — Pull-Up Resistor.

RS-232 — EIA Recommended Standard 232. “A standard for serial communication transmission of data. It formally defines the signals connecting between a DTE (data terminal equipment) such as a computer terminal, and a DCE (data circuit-terminating equipment or data communication equipment), such as a modem. The RS-232 standard had been commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. An RS-232 serial port was once a standard feature of a personal computer, used for connections to modems, printers, mice, data storage, uninterruptible power supplies, and other peripheral devices. RS-232, when compared to later interfaces such as RS-422, RS-485 and Ethernet, has lower transmission speed, short maximum cable length, large voltage swing, large standard connectors, no multipoint capability and limited multidrop capability. In modern personal computers, USB has displaced RS-232 from most of its peripheral interface roles. Many computers no longer come equipped with RS-232 ports (although some motherboards come equipped with a COM port header that allows the user to install a bracket with a DE-9 port) and must use either an external USB-to-RS-232 converter or an internal expansion card with one or more serial ports to connect to RS-232 peripherals.”[WIKI]

RTCReal Time Counter.

Rx —

servo, servomotor —

servo control — Servo control is achieved by sending a servo a PWM signal, a series of repeating pulses of variable width where the width of the pulse determines the position to be achieved by the servo. The PWM signal might come from a radio control receiver to the servo or from common microcontrollers such as the Arduino.

shield — Arduino and Arduino-compatible boards use printed circuit expansion boards called shields, which plug into the normally supplied Arduino pin headers. Shields can provide motor controls for 3D printing and other applications, Global Positioning System (GPS), Ethernet, liquid crystal display (LCD), or breadboarding (prototyping). Several shields can also be made do it yourself (DIY).

Schottky diode — A semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage drop and a very fast switching action. When sufficient forward voltage is applied, a current flows in the forward direction. A silicon diode has a typical forward voltage of 600–700 mV, while the Schottky’s forward voltage is 150–450 mV. This lower forward voltage requirement allows higher switching speeds and better system efficiency. Not to be confused with Shockley diode.

Shockley diode — Not to be confused with Schottky diode.

SOIC — Small Outline Integrated Circuit. A surface-mounted integrated circuit (IC) package which occupies an area about 30–50% less than an equivalent dual in-line package (DIP), with a typical thickness that is 70% less. They are generally available in the same pin-outs as their counterpart DIP ICs. The convention for naming the package is SOIC or SO followed by the number of pins. For example, a 14-pin 4011 would be housed in an SOIC-14 or SO-14 package.


SPI — Serial Peripheral Interface. “A synchronous serial communication interface specification used for short distance communication, primarily in embedded systems. The interface has become a de facto standard. Typical applications include Secure Digital cards and liquid crystal displays. SPI devices communicate in full duplex mode using a master-slave architecture with a single master. The master device originates the frame for reading and writing. Multiple slave devices are supported through selection with individual slave select (SS) lines. The SPI may be accurately described as a synchronous serial interface, but it is different from the Synchronous Serial Interface (SSI) protocol, which is also a four-wire synchronous serial communication protocol. SSI Protocol employs differential signaling and provides only a single simplex communication channel.”[WIKI]


stepper motor —

TTL — Transistor–transistor logic. “TTL is a class of digital circuits built from bipolar junction transistors. It is so named because transistors perform both the logic function and the amplifying function (unlike resistor–transistor logic and diode–transistor logic). TTL integrated circuits (ICs) were widely used in applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, and synthesizers. The 7400 series by Texas Instruments became particularly popular. TTL manufacturers offered a wide range of logic gates, flip-flops, counters, and other circuits. Variations of the original TTL circuit design offered higher speed or lower power dissipation to allow design optimization.”[WIKI]

Tx —

UART — Universal Asynchronous Receiver-Transmitter. A computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. The electric signaling levels and methods are handled by a driver circuit external to the UART. A UART is usually an individual (or part of an) integrated circuit (IC) used for serial communications over a computer or peripheral device serial port. UARTs are now commonly included in microcontrollers. A related device, the universal synchronous and asynchronous receiver-transmitter (USART) also supports synchronous operation.

Uno — Arduino Uno board. The Uno Rev3 board is 2.7 in × 2.1 in (68.6 mm × 53.3 mm) and has a 16 MHz ATmega328P processor, 32 kB flash, 1 kB EEPROM, 2 kB SRAM, USB 16U2 host interface, 6 analog input pins, 14 digital I/O pins, 6 of the digital I/O pins with PWM, and runs on 5 volts.

USART — Universal Synchronous and Asynchronous Receiver-Transmitter.

VCC, VCC — Logic power voltage. Positive supply voltage for bipolar junction transistor.

VDD, VDD — Drain power voltage. Positive supply voltage for field-effect transistor.

VEE, VEE — Ground reference or source power voltage (pin). Negative supply voltage for bipolar junction transistor.

VI — Input voltage.

VIH — High-level input voltage.

VIL — Low-level input voltage.

virtual memory — Virtual memory is “a memory management technique that provides an “idealized abstraction of the storage resources that are actually available on a given machine” which “creates the illusion to users of a very large (main) memory.” The computer’s operating system, using a combination of hardware and software, maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage, as seen by a process or task, appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer. The primary benefits of virtual memory include freeing applications from having to manage a shared memory space, increased security due to memory isolation, and being able to conceptually use more memory than might be physically available, using the technique of paging.”[WIKI]

VO — Output voltage.

VOH — High-level output voltage.

VOL — Low-level output voltage.

VSS, VSS — Ground reference or source power voltage (pin). Negative supply voltage for field-effect transistor.

Watchdog Timer —

Wiegand — [TODO: Used in access control systems.]

Wheatstone bridge — “A 4-arm bridge forming a diamond, all of whose arms are predominantly resistive, with three resistors of known values in three of the arms and the unknown resistor in the fourth. NOTE 1: A voltage source, e.g., a battery, is connected across two opposite points of the diamond and a current-detecting instrument (e.g., a galvanometer) is connected across the other two points. The values of one or two of the known resistors are varied until no current flows through the galvanometer. The bridge is then balanced and the value of the unknown resistor can be calculated in terms of the other three. NOTE 2: A method using the Wheatstone bridge for monitoring resistance of solder bumps in electromigration tests has greater sensitivity to resistance change than other methods. Net resistance changes due to electromigration of only the solder bumps, excluding the Al or Cu traces, can be deduced by this method.”[JEDEC]

zero-ohm resistor — “A zero-ohm link or zero-ohm resistor is a wire link used to connect traces on a printed circuit board that is packaged in the same physical package format as a resistor. This format allows it to be placed on the circuit board using the same automated equipment used to place other resistors, instead of requiring a separate machine to install a jumper or other wire. The resistance is only approximately zero; only a maximum (typically 10–50 mΩ) is specified. A percentage tolerance would not make sense, as it would be specified as a percentage of the ideal value of zero ohms (which would always be zero), so it is not specified. An axial-lead through-hole zero-ohm resistor is generally marked with a single black band, the symbol for “0” in the resistor color code.”[WIKI]



[ARD]Arduino (Official Website)”. Arduino. ( 2018-02-05)

[JEDEC] “Dictionary Introduction”. JEDEC. ( 2018-02-05)

[WIKI] Wikipedia. ( 2018-02-05)

[WIKIROHS] Wikipedia contributors. “Restriction of Hazardous Substances Directive”. Wikipedia. January 22, 2018. ( 2018-02-05)