And it feels like medication

Electric charge

A basic property of matter, positive or negative, that makes particles attract or repel each other. Moving charge is what carries electricity through wires.

Electric current

The flow of electric charge through a material, measured in amperes (amps). Like the amount of water passing a point in a pipe each second.

Voltage

The electrical push that drives current, measured in volts. Like water pressure: a higher voltage pushes harder on the charge in a wire.

Resistance

How strongly a material opposes current, measured in ohms. Like a narrow pipe: for the same push, more resistance lets less current through.

Impedance

How much a circuit opposes alternating or fast-changing current. It is like resistance, but it also depends on how fast the signal changes.

Ohm's law

The rule linking the three basics: voltage equals current times resistance. Know any two and you can calculate the third, which is how nearly every circuit gets sized.

Electrical power

How fast energy is being used, measured in watts: volts times amps. Much of it ends up as heat, so parts have limits on how much they can handle.

Pico (p)

A prefix meaning one trillionth. A picoamp is a trillionth of an amp, a vanishingly small current.

Nano (n)

A prefix meaning one billionth. A nanosecond is a billionth of a second, the time light takes to travel about 30 centimeters.

Micro (µ)

A prefix meaning one millionth. A microvolt is a millionth of a volt.

Milli (m)

A prefix meaning one thousandth. A milliamp is a thousandth of an amp, a typical size for currents on a small board.

Kilo (k)

A prefix meaning one thousand. A kilohm is a thousand ohms.

Mega (M)

A prefix meaning one million. A megohm is a million ohms.

Conductor

A material such as copper that lets current flow easily, like a wide open pipe.

Insulator

A material such as plastic or air that blocks current, like a closed valve.

Semiconductor

A material whose ability to conduct electricity can be controlled, acting as a conductor or an insulator as needed. That control is what lets chips switch and compute. Silicon is the usual one.

Silicon

The semiconductor nearly all chips are made from. Thin slices of purified silicon are etched with microscopic circuits.

Signal

A voltage or current that varies over time to carry information, such as a sensor reading or a stream of bits.

Chip (IC)

An integrated circuit: a whole circuit etched onto a tiny sliver of silicon and sealed in a small plastic package with pins. Like a program compiled into hardware.

Pin (of a chip)

One of the metal connections on a chip's package where signals and power go in and out. Like the chip's API: the only way to talk to it.

Package (of a part)

The physical body around a part, together with its pins or pads. One chip can come in several packages with different sizes and pin layouts.

Circuit

A closed loop from a power source's positive side, through the parts, and back to its negative side. Current flows only when the loop is complete, like water pumped around a closed loop of pipe.

Schematic

A diagram showing which parts connect to which, without caring where they sit on the board. It is like a wiring flowchart, often split into sheets by function such as power or microcontroller.

Schematic sheet

One page of a schematic. A big design is split across several sheets, usually one per function, like files in a project.

Open circuit

A break in the loop, such as a cracked trace or an unsoldered pin, so no current flows. Like a drawbridge left up.

Short circuit

An accidental easy path between two points at different voltages, with almost no resistance. Current surges, and parts or traces can overheat and burn out.

Printed circuit board (PCB)

A flat board of insulating material, usually fiberglass epoxy called FR-4, with copper patterns that connect the parts soldered onto it. It is the wiring and the mounting surface in one.

Trace (PCB)

A narrow copper strip on a board that carries a signal or power from one part to another. It is the board's version of a wire.

Pad (PCB)

Exposed copper on a board where a part's lead or terminal is soldered. The part's electrical connection to the board.

Solder

A metal alloy that melts at a low temperature and, once cooled, joins a part's pin to the copper of a board both mechanically and electrically.

Ground (GND)

The shared reference point for voltages, defined as 0 volts, and the path current takes back to the source. Like sea level: every other voltage is measured relative to it.

Rail

A wire or board area held at a steady supply voltage that the parts run on. Boards have several, each named for its voltage relative to ground.

3V3 (rail name)

The name of a rail held at 3.3 volts above ground, a common supply for chips. Other rails follow the same pattern, such as 5V for 5 volts.

VCC (supply name)

The label for a chip's positive supply connection, the pin that brings in its power. VDD is another name for the same connection.

DC (direct current)

Current that flows in one direction at a steady voltage, as from a battery. Boards run on DC, even though signals on them can change very quickly.

AC (alternating current)

Current that reverses direction many times a second, as from a wall outlet. It has to be converted to DC before it can power a board.

Series connection

Parts wired one after another in a single path, so the same current passes through every one. Like cars in a single lane.

Parallel connection

Parts wired side by side across the same two points, so each has the same voltage across it. Like several lanes branching off one road and rejoining.

Net (circuit)

A group of points that are all electrically connected, such as every pin tied to one supply rail.

Noise (electrical)

Unwanted small variations in voltage or current, from switching parts, nearby signals or the supply. Like static on a radio, it hurts most when the real signal is tiny.

Pulse-width modulation (PWM)

Controlling power by switching a signal on and off very fast and changing how long it stays on each cycle. A longer on-time delivers more average power, like flicking a light switch rapidly to dim it.

Duty cycle

The fraction of each cycle that a switched signal spends on. A 25 percent duty cycle means on a quarter of the time, so the average power is a quarter of full.

Analog signal

A signal whose voltage can take any value within a range, such as a sensor's output. Like a dimmer dial rather than an on-off switch.

Digital signal

A signal with only two levels, low and high, standing for 0 and 1. Like a light switch that is either off or on.

Signal edge

The moment a digital signal switches from low to high (rising edge) or high to low (falling edge). Chips often act exactly when an edge arrives.

Logic level

The voltage ranges that count as low or high. Near ground is low, near the supply voltage is high. Parts using different logic voltages cannot always talk directly.

Active-low signal

A signal that does its job when held low and stays idle when high, the reverse of the usual. A reset line is typical, and its name often carries a bar or an N.

Cycle

One full run of a repeating signal, from a starting point until it returns to that same point, such as high, then low, then high again.

Frequency

How many cycles happen each second, measured in hertz. A million repeats a second is one megahertz. At higher frequencies board layout matters more.

Electrical load

Anything that draws power from a supply, such as an LED, a motor or a chip. The supply exists to feed the load.

Battery

A part that stores chemical energy and supplies it as DC voltage between its positive and negative terminals. It powers a portable device away from wall power.

Coin cell

A small, flat, round battery the size of a coin. It supplies a small current for a long time, for example to keep a clock running.

Switch

A part that opens or closes a circuit, by hand or under electrical control. Open stops the current, closed lets it flow. Like a faucet that is fully on or off.

Fuse

A part with a thin link that melts when too much current passes through, opening the circuit to protect the rest of the board. It must be replaced once blown.

Polyfuse (resettable fuse)

A fuse that becomes very resistant when too much current heats it, cutting the current off, then recovers as it cools. Like a circuit breaker rather than a one-shot fuse.

USB-C

A small, reversible connector standard that carries both power and data over one cable. Devices use it for charging and for talking to a computer.

Sensor

A part that turns something in the physical world, such as light, magnetic field or motion, into an electrical signal a chip can read.

Amplifier

A circuit that makes a signal larger without changing its shape. Needed when a sensor's output is too weak to use directly.

Gain

How many times larger an amplifier's output is than its input. A gain of 10 turns a 1 millivolt signal into 10 millivolts.

Feedback

Sending part of a circuit's output back to its input so the circuit corrects itself, like a thermostat. It makes an amplifier's gain predictable and a power supply's voltage steady.

Electronic filter

A circuit that passes some frequencies and blocks others, for example removing hum or fast noise from a signal.

Converter (circuit)

A circuit that changes electricity from one form into another, for example one voltage into a different voltage. Buck and boost converters are the common kinds.

Voltage regulator

A circuit that turns a varying or higher voltage into one steady voltage for the chips to run on, like a pressure regulator on a water line.

Linear regulator

A power circuit that lowers a voltage by burning the excess as heat. Simple and quiet, but wasteful when the input is much higher than the output.

LDO (low-dropout regulator)

A linear regulator that keeps working even when its input is only slightly above its output. The dropout is the smallest gap it needs between the two.

Switching regulator

A power circuit that switches current on and off very quickly through a coil to change a voltage with little wasted heat. More efficient than a linear regulator, but it adds switching noise.

Buck converter

A switching converter that steps a voltage down, switching rapidly with an inductor so very little power is wasted as heat.

Boost converter

A switching converter that steps a voltage up, switching rapidly with an inductor so very little power is wasted.

Buck-boost converter

A switching converter that can step a voltage either up or down, suiting a source whose voltage moves above and below what the load needs.

Clock signal

A steady repeating tick that chips use to keep time and step through their work, like a metronome.

Driver circuit

A circuit that supplies the right power at the right moment to something a signal pin cannot run directly, such as an LED, a laser or a motor.

Constant-current driver

A driver that holds the current through an LED or laser steady even when the voltage changes, because these parts are controlled by current, not voltage.

Bias (electrical)

A steady voltage or current applied to a part so it sits in the state where it works well. A light sensor called a photodiode, for example, can be biased with a high voltage to make it more sensitive.

Data bus

A set of shared wires that several chips use to exchange data in turn, like a shared road. A serial bus sends data one bit after another over few wires.

Laser

A light source that makes a narrow beam of a single color, with all of its light waves moving in step. The beam stays tight over long distances.

Pulse

A very short burst of light or electricity that starts at a known moment, which makes it useful for measuring time.

Wavelength

The length of one wave of light, which sets its color. Infrared has a longer wavelength than red, so the eye cannot see it, though cameras and sensors can.

Infrared (IR) light

Light with a wavelength longer than red, invisible to people. A device can use it unnoticed, but an invisible laser can still injure eyes.

Emitter (light)

Any part that gives off light, such as an LED or a laser.

Channel (circuit path)

One independent path of a circuit, such as one light emitter with its own switch. Several channels repeat the same path side by side.

Ringing (signal)

A brief wobble after a fast edge, before the signal settles, like a bell still vibrating after being struck. Faster edges make it more likely.

Laser range finder

A device that measures distance by sending a short laser pulse at a target, catching the reflected light, and timing the trip. Distance is half the round-trip time multiplied by the speed of light.

Why a range finder needs fast electronics

Light travels so fast that the round trip to a nearby target takes only billionths of a second. The electronics must therefore time events at the nanosecond scale.

Measuring the round-trip time

A fast counter, driven by a very fast clock, starts when the pulse leaves and stops when the echo arrives. The number of ticks counted is the round-trip time.

Why a range finder uses short light pulses

A short, strong flash gives a sharp start time to measure from, and the light source has little time to heat up. A steady beam would give neither.

Why a range finder boosts the battery voltage

A laser pulse and a light detector work best at voltages above the battery's, so boost converters raise the battery voltage for them.

Via

A small plated hole that connects copper on different layers of a board, like a stairwell between floors.

Mounting hole

A hole through the board for a screw, to fasten it into a housing. It usually has no electrical job.

Fiducial

A small round copper marker that the assembly machine looks at to line itself up with the board, like a registration mark.

Test point

An exposed pad on a net where a probe can touch to measure the signal during testing, like a debug port for hardware.

Copper layers

A board can have two or many copper layers separated by insulation. Outer layers hold the parts, and inner layers are often given to ground and power planes.

Ground plane

A large area of copper reserved for ground. It gives current an easy return path, reduces noise and helps spread heat.

Solder mask

The coating, often green, over a board's copper except the pads. It keeps solder from bridging between neighbors and protects the copper.

Silkscreen (PCB)

The printed text and outlines on a board, such as part names, polarity marks and pin 1 dots. Labels for humans building and debugging it.

Through-hole part

A part whose legs go through holes in the board and are soldered on the other side. Sturdy, but larger than a surface-mount part.

Lead (of a part)

A metal leg of a part, the way electricity enters and leaves it. Through-hole parts have leads that go through the board.

Surface-mount part

A part that sits flat on pads on the board's surface. Smaller than a through-hole part, and machines place it easily.

0402 (size code)

A package size code for a tiny surface-mount part, 0.04 by 0.02 inches. About the size of a grain of sand and hard to place by hand.

0603 (size code)

A package size code for a small surface-mount part, 0.06 by 0.03 inches. Slightly larger than 0402 and easier to solder by hand.

Thermal pad

A large exposed metal pad under a chip that is soldered to the board's copper. It carries heat away from the chip and often doubles as ground.