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Series circuit
Series means one unbranched current path. R1 and R2 add together; neither resistor uses up current. I = 5 / (R1 + R2). The larger resistor gets more voltage. Swapping their order does not change total current. V(R2) is the voltage across R2.
Parallel circuit
Parallel branches connect to the same two nodes, so each receives 5 V. A node is a continuous electrical connection. I(R1) = 5/R1 and I(R2) = 5/R2. Total current is their sum. A smaller branch resistance draws more current; adding a branch increases supply current.
Potentiometer / wiper
A potentiometer is a three-terminal variable resistor. Its moving contact is the wiper. Here it divides a 10 kΩ track into R1 above and R2 below. Vout = 5 × position/100. R1 + R2 stays 10 kΩ, so supply current stays 0.5 mA. Turning the knob changes the ratio, not the total resistance.
Diode / anode / cathode
A diode conducts mainly in one direction. D marks the diode, R the current-limiting resistor. The bar on its symbol is the cathode; the other terminal is the anode. Forward current is (5 − 0.7)/R. Reversing the diode blocks current in this model. V(D) is measured from anode to cathode, so it becomes negative in reverse. A real diode has a reverse-voltage limit.
NTC — Negative Temperature Coefficient / thermistor
NTC means Negative Temperature Coefficient: resistance falls as temperature rises. A thermistor is a temperature-sensitive resistor. Here it forms a divider with a fixed 10 kΩ resistor. R(T) = 10000 × exp[3950 × (1/(T + 273.15) − 1/298.15)]. The formula uses absolute temperature in kelvin. Warming reduces the upper resistance, so Vout rises. Real sensors need calibration. Beta is a model constant describing temperature sensitivity. K means kelvin, an absolute temperature unit. exp(x) means e raised to x; e is about 2.718. You do not need to calculate this by hand to explore the sensor.
Light-emitting diode
A semiconductor component that emits light when forward current flows. In this circuit, a resistor limits that current.
Light-dependent resistor
A light-sensitive resistor. In this model, more light means less resistance; the second resistor turns that change into a voltage.
n-type / p-type / n-type transistor
N–P–N describes three semiconductor regions: n-type, p-type, n-type. Electrons are the majority carriers in n-type material; holes in p-type. Here a small base current controls the LED current.
Resistor–capacitor circuit
R means resistance, C means capacitance. Together they set how quickly the capacitor voltage changes.
Analog-to-digital converter
An analog-to-digital converter measures a voltage and represents it as a number. Analog means a continuously varying quantity; digital means discrete codes. The reference sets the measurement range. A converter does not create the sensor signal, and its input must stay within permitted limits.
B = base, C = collector, E = emitter: the transistor’s three terminals. Here the base controls conduction; the LED current flows through collector and emitter.
VBE is base-to-emitter voltage; VCE is collector-to-emitter voltage. The second terminal is the reference. Ib and Ic mean base current and collector current.
Rb is the base resistor; Rc is the collector-branch resistor. R1 and R2 identify different resistors; the numbers do not specify their values.
V = volt (voltage); A = ampere (current); mA = 0.001 A. Ω = ohm (resistance); kΩ = 1000 Ω. F = farad (capacitance); µF = 0.000001 F. s = second; W = watt (power). I means current; Vs supply voltage; Vf diode forward voltage; Vout output voltage; Vc capacitor voltage; τ = R × C is the time constant.
Electrical power / watt
Power is the rate of energy transfer. A watt (W) is one joule of energy per second. For a steady voltage and current, P = V × I: voltage times current. A resistor turns electrical energy into heat; its watt rating limits safe dissipation.
Pull-up resistor
A resistor connects an input to the positive supply, giving it a defined high level when a switch is open. High means a voltage read as logic 1. Closing the switch to ground produces low, logic 0; the resistor limits current through the switch.
Floating input
An input is floating when nothing establishes its voltage. Tiny leakage currents and nearby electrical signals can then change the reading. An open switch alone does not guarantee logic 0. A pull-up or pull-down resistor provides a defined resting state.
Pulse-width modulation
Pulse-width modulation repeatedly switches a signal on and off. Changing the fraction of each cycle spent on changes average delivery to a load. The pulses retain their full height; PWM is not a steady intermediate voltage unless filtered. Loads and drivers have current limits.
Duty cycle
Duty cycle is on-time divided by the duration of one complete cycle, usually expressed as a percentage. With pulses between 0 V and 5 V, 25% duty gives a time-average voltage of 1.25 V. This average is not a promise of equal perceived brightness.
Frequency / hertz
Frequency counts repeated cycles per second. One hertz (Hz) means one cycle each second. Period is the duration of one cycle: frequency = 1/period. A 100 Hz signal has a 10 ms period; ms means millisecond, one thousandth of a second.
Resolution / bit depth
Resolution describes how finely a converter divides its range. A bit is a binary digit, 0 or 1. An N-bit converter has 2^N possible codes: 8 bits gives 256. More codes make finer steps, but do not automatically improve accuracy or remove electrical noise.
Quantization
Quantization assigns a continuous measurement to one of a finite set of codes. Small voltage changes can leave the code unchanged. In an ideal N-bit converter the nominal step width is range/2^N. Quantization creates uncertainty even with perfect components; actual conversion boundaries depend on the device.
Resistor–capacitor low-pass filter
RC means resistor–capacitor. With a resistor in series and a capacitor from the output to ground, this low-pass filter follows slow changes and reduces rapid changes. The capacitor voltage cannot jump instantly. These relations assume an ideal source and a lightly loaded output.
Cutoff frequency
For this ideal resistor–capacitor filter, cutoff is 1/(2πRC), with resistance R in ohms and capacitance C in farads. π is about 3.1416. At cutoff the output sine-wave amplitude is about 70.7% of the input; it does not abruptly become zero above that frequency.
555 timer
The 555 is a timer chip that can make a single timed pulse or repeated pulses. External resistors and a capacitor set timing. In the standard arrangement its internal comparisons use roughly one-third and two-thirds of the supply voltage. Different 555 versions have different operating limits.
Operational amplifier
An operational amplifier amplifies the voltage difference between its + and − inputs. Feeding some output back to the − input can set predictable gain. Gain means output change divided by input change. Its supply, input range, speed and output current limit what it can do.
Voltage buffer / voltage follower
A voltage buffer, or voltage follower, uses an operational amplifier with its output connected to its − input. The + input receives the signal. Within operating limits, the output follows that voltage while drawing little current from the source. It reduces loading; it does not create unlimited power.
Voltage comparator
A comparator decides which of two input voltages is higher and changes its output state accordingly. It can turn a smooth sensor voltage into an on/off decision. The input range and output wiring depend on the part; an operational amplifier is not always a suitable substitute.
Hysteresis
Hysteresis uses separate thresholds for switching on and switching off. Between them, the output keeps its previous state. This prevents repeated switching when a noisy signal hovers near a boundary. A temperature controller might turn on at 30 °C and off at 28 °C.
Metric prefixes and units
A prefix scales a unit: milli (m) means 1/1000, micro (µ) 1/1000000 and nano (n) 1/1000000000. mW is milliwatt, a power unit; ms is millisecond, a time unit. nF is nanofarad and µF is microfarad, units of capacitance: a capacitor’s ability to store charge per volt. Hz is hertz, cycles per second. A bit is a binary digit, 0 or 1.
Internal resistance
A source can be represented by an ideal voltage in series with internal resistance Ri. Load current causes a voltage drop I × Ri and internal loss I² × Ri. This simple equivalent circuit, often called a Thevenin model, does not predict battery life or chemistry.
Wheatstone bridge
Four resistors form two voltage dividers. Comparing their middle voltages reveals an imbalance; matching the two resistance ratios gives zero difference. A sensor changes one arm, while a trim resistor adjusts balance. The meter is assumed not to load either divider.
Metal Oxide Semiconductor Field Effect Transistor
MOSFET means Metal Oxide Semiconductor Field Effect Transistor. Gate-to-source voltage VGS controls a conducting channel between drain and source; an n-channel device uses electrons as its mobile carriers. RDS(on) is drain-to-source resistance when driven on. Threshold voltage indicates the start of conduction, not guaranteed low resistance. VDS is drain-to-source voltage; here the source is at 0 V.
Zener diode
A Zener diode is designed to operate in reverse breakdown. With a series resistor limiting current, it can hold a node near its specified voltage. Load current and Zener current share the available supply current. Too little Zener current loses regulation; too much dissipates excessive power.
Resistor Capacitor high-pass filter
RC means Resistor Capacitor. A series capacitor and resistor to ground pass rapid changes better than slow ones; output is measured across the resistor. For an unloaded sinusoid, cutoff is fc = 1/(2πRC). Gain at cutoff is about 70.7%, and steady direct current is blocked in the ideal model.
Resistor Inductor circuit
An inductor stores energy in a magnetic field and opposes changes in current. RL means Resistor Inductor: resistance and inductance set the time constant τ = L/R. L is inductance in henries; mH is 1/1000 H. Energy is L × I²/2; mJ is 1/1000 joule. Interrupting current can create a large voltage, outside this step model.
Resistor Inductor Capacitor circuit
RLC means Resistor Inductor Capacitor. In a series sinusoidal circuit, inductive reactance XL rises with frequency and capacitive reactance XC falls. Reactance is opposition associated with energy storage, measured in ohms. At f0 = 1/(2π√(LC)), the reactances cancel and resistance limits current; resonance does not create energy.
Full-wave bridge rectifier
AC means Alternating Current: its direction reverses. DC means Direct Current: it flows in one direction, although its magnitude may vary. A four-diode bridge sends both input half-cycles through the load in the same direction; two diodes conduct at once. Output pulses repeat twice per input cycle and require additional filtering to become smooth.
Inverting operational amplifier
A powered operational amplifier with negative feedback produces opposite-polarity output. In the linear ideal model, voltage gain is −Rf/Rin. Its inverting input is near 0 V when the other input is grounded: a virtual ground, not a wire to ground. Output clipping at the supply limits breaks that approximation.
Non-inverting operational amplifier
A signal applied to the positive input keeps its polarity. Negative feedback divides the output back to the other input, setting ideal voltage gain 1 + Rf/Rg. Rg connects to ground and Rf to output. If the required output exceeds the supply range, clipping occurs and the two input voltages need not match.
NOT AND logic gate
NAND means NOT AND: invert the result of AND. The output is logic 0 only when both inputs are logic 1; all other defined input pairs give logic 1. A truth table lists these four cases. NAND gates can build other logic functions, but physical devices have voltage thresholds and propagation delay.
Monostable one-shot timer
Monostable means one stable resting state. A trigger starts a temporary output pulse before the timer returns to rest. An ideal 555 timer charges a capacitor to two thirds of its supply, giving T = ln(3) × R × C, about 1.099RC. R is resistance, C capacitance; ms is 1/1000 second. The elapsed-time slider samples one pulse.
Comparator
A comparator compares two input voltages and produces a high or low output rather than a scaled copy of their difference. A reference voltage is the comparison target; a threshold is the level at which the decision changes. In this non-inverting teaching model, input above reference gives 5 V and input at or below reference gives 0 V. Equality is a chosen rule, not a prediction for real hardware: offset, noise, response delay and output circuitry matter. Supply rails are the power connection voltages that bound the output.
Schmitt trigger
A Schmitt trigger changes state at two different input thresholds. Hysteresis means the output also depends on its previous state: in the band between thresholds it remembers that state. Here input at or above 3 V sets the output high, and input at or below 2 V resets it low. The 1 V separation is the hysteresis band. Positive feedback returns part of the output to reinforce a change; real circuits can use it to create the two thresholds. This non-inverting model uses prescribed thresholds and no physical feedback-resistor calculation.
Electromagnetic relay
An electromagnetic relay uses a current-carrying coil to move mechanical contacts, which make or break another circuit. NO means Normally Open: the contact is open with the coil released. NC means Normally Closed: the contact is closed with the coil released. A coil is an inductor with winding resistance; the contact circuit and coil circuit can be electrically isolated, but that does not mean unlimited voltage or current ratings. This experiment calculates coil-current decay only, not contact motion or a certified isolation rating.
Flyback diode
A flyback diode provides a circulating-current path when a direct-current coil is switched off. During normal energizing it is reverse biased, meaning its orientation blocks supply current: cathode, the striped end on many diodes, is toward the positive coil supply; anode is toward the switched end. After switch-off the coil reverses its terminal voltage to keep current flowing, and the diode conducts. This model uses a fixed 0.7 V forward drop and winding resistance. Suppression changes the current decay; a low-voltage clamp can make relay release slower than a higher-voltage clamp.
Electromotive Force
EMF means Electromotive Force, an induced voltage measured in volts; despite the name it is not a mechanical force. Back EMF opposes a change in current as the coil’s magnetic field changes. With the passive voltage convention, voltage across the ideal inductive part is L × dI/dt: L is inductance and dI/dt means the rate of current change. A real winding also has a resistive voltage drop. A flyback path limits switch-off voltage by allowing current to continue. Field energy is dissipated in winding and diode, not instantly erased.
Contact bounce
Contact bounce is a short sequence of unwanted open/closed changes while mechanical contacts settle after switching. It comes from their motion, not from a comparator changing its decision near an electrical threshold. Debouncing means accepting a switch state only after such changes have settled, using timing or a suitable circuit. Hysteresis alone does not guarantee debouncing of full-amplitude contact transitions. The relay experiment has no contact-motion or bounce model, so its smooth coil-current curve cannot predict bounce time.
Set Reset latch
SR means Set Reset: set writes 1, reset writes 0. A latch stores one bit, a binary digit that is 0 or 1. Two NOR (NOT OR) gates feed their outputs back to each other. A NOR output is 1 only when both inputs are 0. Here logic 1 is 5 V and logic 0 is 0 V. S is set, R is reset, Q is stored output, and Q̅ is its opposite in valid operation. With S = R = 0, feedback keeps the previous bit. Both commands at 1 force both outputs to 0, so they cease to be opposites. Ideal active-high inputs: 1 activates the command. S = R = 1 is invalid. Releasing both then leaves memory uncertain until one command acts. Power off resets this teaching model to 0; a real latch has no guaranteed power-up state. Delays and noise are omitted. Use Release both inputs to return S and R to 0 together.
NOT OR logic gate
NOR means NOT OR: take OR, then reverse its answer. OR is 1 if either input is 1; NOR therefore is 1 only with both inputs 0. Feeding two NOR outputs back to each other can retain a bit. A single gate alone has no memory. Real gates have voltage thresholds, delays and load limits.
Digital to Analog Converter
DAC means Digital to Analog Converter: it turns a number into a voltage. An R–2R ladder combines resistors of resistance R and twice R. A bit is 0 or 1. LSB (Least Significant Bit) has weight 1; MSB (Most Significant Bit) has weight 8 here. Four bits select 16 voltage levels. b0 to b3 are input bits with weights 1, 2, 4 and 8. Code is their weighted sum. Vout is output voltage; Vref is reference voltage. One LSB step is Vref/16. Code 15 is one step below Vref, not equal to it. Ideal four-bit voltage ladder with a buffer, a circuit that follows voltage without loading the ladder. The output is unloaded. Reference Vref is 1–5 V. Resistor errors, switch glitches, settling time and output-current limits are omitted.
Least Significant Bit
LSB means Least Significant Bit, the binary position with the smallest weight. In this four-bit converter it is b0, weight 1 in the code. Changing only b0 from 0 to 1 raises ideal output by Vref/16. One LSB step describes resolution, not a guarantee of measurement accuracy.
Most Significant Bit
MSB means Most Significant Bit, the binary position with the largest weight in a word. Here it is b3 with weight 8. With other bits zero, setting b3 gives code 8, half the reference voltage. It is not a sign bit in this unsigned four-bit model; all codes are nonnegative.
Clock
A clock is a repeating timing signal; CLK abbreviates Clock. A rising edge is its change from logic 0 to 1. A binary counter adds one per received rising edge. A bit is a binary digit, 0 or 1; four bits hold 16 states, 0000 to 1111. Hz (hertz) counts cycles per second. n is the number of received edges. The four-bit count is n modulo 16: keep the remainder after division by 16. Q0 is the lowest-weight bit and Q3 the highest. Under continuous counting, Q0 completes one cycle per two edges; Q3 per sixteen. Choose 0–32 already-received edges or press Clock pulse to add one. This is a history sample, not an automatically running clock. Frequency sets steady repeating output rates, not the chosen count. Ideal transitions have no delay or contact bounce. Clock pulse stops at 32 received edges. Reset starts a new sample.
Exclusive OR
XOR means Exclusive OR. For two binary inputs, its output is 1 when the inputs differ and 0 when they match. The symbol ⊕ denotes this operation. Unlike inclusive OR, two high inputs give a low result. Here 0 and 1 describe logic states; the diagram does not calculate chip currents or switching delay.
Truth table
A truth table lists every possible input combination and its resulting output. Two binary inputs need four rows; three need eight. It describes the logical rule, rather than the order in which inputs change. Checking all rows distinguishes a correct circuit from one that happens to work for a single setting.
Half adder
A half adder adds two one-bit values and produces a sum bit S and carry bit C. The sum uses exclusive OR; carry is high only when both inputs are high. The total is S + 2C. It has no carry input, so an isolated half adder cannot include a carry from a previous digit.
Carry bit
A carry bit represents the part of a sum passed to the next binary position. Adding 1 and 1 gives binary 10: sum bit 0, carry bit 1. Carry is itself a binary state, although it contributes a weight of two relative to the current position. C here means carry, not capacitance or transistor collector.
Full adder
A full adder adds three one-bit inputs: A, B and an incoming carry Cin. Its two outputs satisfy A + B + Cin = S + 2Cout. Two half adders and an inclusive OR function can implement it. Connecting one position’s carry output to the next position’s carry input allows addition of wider binary numbers.
Carry input
Cin means Carry input: the incoming carry from a lower binary position. It is a third value to add, rather than an enable switch. For A = B = 0, Cin = 1 gives sum 1 and carry-out 0. The course models one position; propagation between physical stages takes time.
Multiplexer
MUX abbreviates Multiplexer, a circuit that selects one of several inputs for an output. In this two-input model, select S = 0 routes A and S = 1 routes B. It does not average or add the inputs. Actual devices may also have enable controls and different voltage or timing limits.
Select input
A select input chooses which data input reaches a multiplexer’s output. The selector is a control value; it need not equal the selected data value. Here S = 0 chooses A even when A = 1. The letter S means select in this experiment and sum in an adder; read the circuit context.
Binary decoder
A binary decoder turns a binary input code into a selected output line. Two code bits can choose four lines. This model uses code b0 + 2b1 and an active-high enable: E = 1 activates the selected output, E = 0 leaves all outputs low. Other devices can use different enable and output polarities.
One-hot encoding
One-hot encoding uses a group of bits with exactly one high bit to identify a choice. Four one-hot lines can represent four choices, while a two-bit binary code also represents four choices. Here disabling the decoder produces no high lines. That all-zero state is disabled, rather than a fifth one-hot choice.
Parity bit
A parity bit is an extra bit chosen to make the total number of ones even or odd. This experiment generates even parity: P is 1 when the three data bits contain an odd number of ones. A receiver checks the received data together with the originally transmitted P. Parity does not identify the incorrect bit.
Bit error
A bit error changes a digital value from 0 to 1 or from 1 to 0. A parity check detects an odd number of such flips in a protected word, including its parity bit, but an even number can pass undetected. Recomputing the sender’s parity after corrupting the data hides the demonstration; keep the original transmitted parity.
Inverting summing amplifier
A summing amplifier adds input signals. Op amp means Operational Amplifier, a powered circuit that amplifies the difference between two inputs. Negative feedback returns output to the subtracting input. A virtual ground stays near 0 V through feedback, without a wire to ground. V1 and V2 are input voltages. Each contributes current through its own resistor. Their currents add in the feedback resistor Rf. Gain magnitude g = Rf/10 kΩ; output Vout reverses the sum’s sign. Ideal amplifier with ±12 V output limits; two equal 10 kΩ input resistors. The gain knob sets feedback resistance. No noise, bandwidth, load or resistor error is modeled.
Virtual ground
Virtual ground is a circuit node held near ground voltage by negative feedback, rather than by a wire to ground. In the ideal inverting summer, the noninverting input is grounded and feedback adjusts output so the inverting input stays near 0 V. The input currents then meet at this summing node and flow through the feedback resistor. It is not an extra ground terminal or a general power source. The approximation needs a powered amplifier operating with effective feedback; an amplifier at its limits need not hold this voltage.
Difference amplifier
A difference amplifier subtracts one input from another. Op amp means Operational Amplifier, a powered difference-amplifying circuit. Common-mode voltage is the part shared by both inputs. CMRR means Common Mode Rejection Ratio: how well an amplifier rejects that shared part compared with the desired difference. Input difference is V2 − V1. Matching both resistor ratios makes output Vout = g × (V2 − V1). Increasing both inputs equally leaves their difference unchanged. Ideal four-resistor amplifier with exactly matched resistor ratios and ±12 V output limits. Common-mode rejection is perfect here; actual resistor mismatch, input range, noise and bandwidth are omitted.
Common Mode Rejection Ratio
CMRR means Common Mode Rejection Ratio: how strongly a circuit amplifies the wanted difference compared with an unwanted voltage shared by both inputs. The shared component is called common-mode voltage; for two inputs its average is (V1 + V2)/2. Equal changes to both inputs leave their difference unchanged. Precisely matched resistor ratios and an ideal Operational Amplifier give zero gain for the shared component in this lesson, so the ideal rejection ratio is unbounded. No real numerical CMRR measurement is simulated. Real resistor mismatch and amplifier imperfections turn some shared voltage into output error.
Integrator
An integrator accumulates input over time. Op amp means Operational Amplifier, a powered amplifier; a feedback capacitor makes its output remember accumulated charge. An initial condition is the starting value needed before predicting a changing system. Here output starts at 0 V. R means resistance, C means capacitance; RC is their product, a time scale called the time constant. RC = 0.1 s sets the accumulation scale. For a constant input Vin, requested output Vout = −Vin × t/RC. t is elapsed time in seconds; 100 ms is 0.1 s. The minus sign reverses the accumulation. Constant input, R = 10 kΩ and C = 10 µF. Choose an elapsed-time sample, not a running clock. Requested output is clipped at ±10 V. Every calculation starts from 0 V; offsets and leakage are omitted.
Initial condition
An initial condition is the starting value needed to predict a system that changes over time. For the integrator it is the initial capacitor/output voltage, Vout(0). The later output equals that starting value plus the accumulated input effect. This lesson fixes Vout(0) = 0 V on every calculation: moving the elapsed-time slider selects a new sample from the same start, rather than continuing a previous run. A physical capacitor can already hold charge, so its starting voltage cannot generally be assumed zero.
Differentiator
A differentiator responds to a signal’s rate of change, not its final size. Op amp means Operational Amplifier, a powered amplifier. A ramp is a steady voltage change over a finite duration. Slew rate is a real amplifier’s maximum output-voltage change per unit time; that limit is omitted here. R means resistance, C means capacitance; RC is their product, a time scale called the time constant. ΔV is total ramp change and T its duration in seconds. During the ramp the input slope is ΔV/T, and requested output is −RC × ΔV/T. A downward ramp produces positive output. Ideal linear input ramp with R = 100 kΩ, C = 1 µF and RC = 0.1 s. The displayed value is during the ramp. Output limits are ±10 V. No instantaneous step, start/end transient, noise or frequency limit is simulated.
Slew rate
Slew rate is the maximum speed at which a real amplifier can change its output voltage. It is an output limitation, not another name for the input ramp slope. A circuit may ask for a fast change that the real output cannot follow even when its requested voltage stays inside the supply limits. This finite-ramp differentiator calculates an ideal output during the ramp and omits slew rate, frequency limits and start/end behavior. Its selected input change divided by duration describes the input slope, not a measured amplifier slew rate.
Sample and hold
Sample and hold means capture a voltage and retain it for later use. A capacitor stores the selected sample; a buffer follows it without drawing current in this model. Droop means the held voltage drifts during hold. Here a leakage resistor to ground makes it decay. R means resistance, C means capacitance; RC is their product, a time scale called the time constant. Vsample is voltage at the start of hold. Rleak is leakage resistance, C capacitance, and τ = Rleak × C the time constant. Held voltage Vhold = Vsample × exp(−t/τ), with exp(x) meaning e to the power x. Select the initial sampled voltage and elapsed hold time; there is no capture button or live history. C = 1 µF and the leakage path is 100–1000 kΩ. This passive RC model omits real switch, buffer and capacitor leakage mechanisms.
Hold-voltage droop
Droop is a gradual change in a held voltage while a sample is being retained. Here an initially sampled voltage is stored on a capacitor, and a parallel leakage resistor to ground removes charge: Vhold = Vsample × exp(−t/(Rleak C)). Rleak is resistance, C capacitance, t elapsed time; exp(x) means e raised to x. Their product is the time constant. At one time constant about 36.8% remains. This chosen passive leakage gives exponential decay. Real switches, buffers and capacitors can leak in other ways, so droop is not universally exponential or described by one resistance.
Window comparator
A comparator compares voltages and makes a high/low decision. A window comparator combines two comparisons to report whether an input lies between a lower and upper limit. Window width is their difference. Here output is high only strictly inside the interval. Vlow and Vhigh are lower and upper thresholds. Output Vout = 5 V only when Vlow < Vin < Vhigh; otherwise 0 V. The window width is Vhigh − Vlow. Crossing a boundary changes the decision immediately in this model. Ideal 0 V/5 V decisions, no delay, noise or memory. Equality at either boundary is deliberately outside. Two limits do not automatically give hysteresis, where the previous state changes a switching decision.
Control deadband
A control deadband is an input interval in which a controller applies no corrective action. It can avoid reacting to small deviations, but its meaning depends on the controller. It is distinct from this window detector, which reports high when the input is strictly inside an allowed interval. Hysteresis means the previous state changes where switching occurs: upward and downward switching can use different thresholds. A static deadband or two window limits do not by themselves create this memory. The lesson implements an interval test without a controller or hysteresis.
Hobby servo
A hobby servo combines a motor, position sensing and internal control to aim a shaft toward a requested position. A pulse on its control lead encodes the request. This lesson deliberately maps 1–2 ms to 0–180°, with a 20 ms period. Real ranges, direction and calibration vary; the displayed command does not measure a shaft or simulate mechanical response.
Pulse Width
Pulse Width is the time a pulse stays high, here w in milliseconds. ms means millisecond, 1/1000 second. Width differs from period, the time of a whole repeating cycle, and duty, the fraction of that cycle spent high. Servo position commands depend on pulse width; width alone says nothing about motor power consumption.
Control lead
A control lead carries a timing instruction to the servo electronics. Separate supply wires provide motor energy. Controller and motor supply need a common voltage reference so the signal can be interpreted. GND means Ground, that circuit reference; it does not make the thin signal wire a motor power source. The lesson omits supply current and loading.
Stepper motor
A stepper motor advances through discrete shaft steps as a driver sequences magnetic fields in its windings. A winding is a coil of wire. The driver routes power currents, while a command chooses amount and direction. Counting requested steps does not prove actual position: physical motors can miss steps. Here the slider selects one command from zero, not accumulated motion.
Full step
A full step is one complete advance of the chosen stepping sequence. This example chooses 1.8° per full step, so 200 steps command 360°. Other motors have other step angles. Direction sets the sign of angle and turns. Microstepping divides the electrical sequence more finely; it is not modeled here, and finer commands alone do not guarantee more positioning accuracy.
Bipolar stepper drive
Bipolar stepper drive reverses current through each of two independent windings. Bipolar here describes winding-current direction, not semiconductor regions in a transistor. A and B label the coils; + and − mark commanded current direction. The four-state example starts from chosen phase 0. These are functional commands, not measured currents or a specific driver pinout.
Piezoelectric transducer
Piezo is short for piezoelectric. Such material changes shape under an electric voltage; repeated motion can vibrate air and produce sound. A passive piezo sounder needs an external changing drive. Mechanical resonances and the drive circuit affect the result. The lab calculates a waveform; its optional short browser playback is not a calibrated model of a real piezo.
Pitch
Pitch is the perceived height of a sound. For a repeating tone, cycle frequency strongly influences pitch: more cycles per second generally sound higher. Hz means hertz, one cycle per second. Pitch is not loudness. Changing duty alters pulse shape without changing its repetition frequency; actual sound also depends on the device and listener.
Square wave
A symmetric square wave switches between two levels for equal durations, with 50% duty. Here those levels are 0 and V; 25% or 75% makes a general rectangular waveform. Period T lasts one cycle, while duty D is its high-time percentage. The mean is V × D/100, not a constant wire voltage or a measure of piezo loudness.
Ultrasonic sound
Ultrasonic means sound above normal human hearing. An echo is sound reflected back from an object. TOF means Time of Flight, the time a wave takes to travel. Here the chosen echo time includes the outward and return trips. T is air temperature in degrees Celsius, c sound speed, t round-trip time in seconds. c = 331.3 + 0.606T. Distance = c × t/2: halve the journey because the echo travels there and back. 1 ms is 0.001 s. Multiply metres by 100 for centimetres. Dry-air speed approximation for the selected 0–40 °C temperature. Choose a valid round-trip echo; this model does not detect obstacles, false echoes, humidity or air gradients. It is a calculation, not a live sensor.
Reflected sound
An echo is sound reflected from a surface and returning toward a receiver. Its delay can reveal a path length when sound speed is known. Real echoes depend on shape, orientation and the medium; multiple reflections can produce confusing returns. This lesson starts from a chosen valid echo time, rather than predicting whether an object produces a detectable echo.
Time of Flight
TOF means Time of Flight, the travel time of a wave. It may describe a one-way path or a round trip; the convention must be stated. Here the measured delay includes both directions, so object distance is speed × time/2. Temperature supplies an approximate dry-air sound speed, not a complete model of humidity, wind or reflections.
Wheatstone bridge
A Wheatstone bridge compares two voltage dividers, each made from two resistors. Balance means their middle voltages are equal, so their difference is zero. Vs is supply voltage and Rs the chosen sensor resistance. mV means millivolt: 1 mV = 0.001 V. Left divider: Vleft = Vs/2. Right divider: Vright = Vs × Rs/(1000 + Rs). Display the signed difference Vright − Vleft in millivolts. Increasing the lower-right resistance raises its midpoint. Three fixed 1000 Ω resistors and one chosen 800–1200 Ω resistance. Midpoint readings are unloaded: the meter draws no current. No amplifier, real strain measurement, heating or resistor errors are modeled.
Bridge balance
Bridge balance means the two divider midpoints have equal voltage, giving zero difference even when neither is at ground. Matching divider ratios is the condition; all four resistors need not always be equal. Here three resistors are 1000 Ω, so the chosen fourth also balances at 1000 Ω. Zero difference is not zero supply voltage.
Strain gauge
A strain gauge is a resistive sensor whose resistance changes as its attached material stretches or compresses. Strain is change in length divided by original length. A bridge can turn resistance change into a voltage difference. The lesson selects resistance directly: it provides neither a gauge calibration nor a force, weight or deformation measurement. Real measurements also depend on temperature and mounting.
Universal Asynchronous Receiver/Transmitter
UART means Universal Asynchronous Receiver/Transmitter, hardware that sends and receives bits in sequence without a shared clock wire. A byte is eight bits. Baud is symbols per second; one binary symbol carries one bit here. 8N1 means eight data bits, No parity check bit, one stop bit. LSB means Least Significant Bit, the smallest-weight bit, sent first. ASCII means American Standard Code for Information Interchange, a 7-bit character code: 65 is A, 85 is U; 255 is outside ASCII. Idle is 1. A frame is start 0, eight data bits b0 through b7, then stop 1: ten bit periods. Bit time = 1000000/baud in µs; frame time = 10000/baud in ms. Idle time between frames is not included. Static logic frame, not a live transmitter or receiver. µs means microsecond, 0.000001 s. ms means millisecond, 0.001 s. Timing mismatch, voltage interfaces, noise and error checking are omitted.
Baud rate
Baud rate counts signal symbols per second, not the number of transitions between high and low. In this binary UART model every symbol carries one bit, so baud equals total bit rate. An 8N1 frame occupies ten periods for eight data bits. Consecutive frames at 9600 baud carry at most 960 bytes/s here, excluding extra gaps; byte content does not change the period.
American Standard Code for Information Interchange
ASCII means American Standard Code for Information Interchange, a standard 7-bit character code with values 0–127. Some values are control codes rather than printed characters. Uppercase A is 65 and U is 85. They fit in an eight-bit byte with the highest bit zero; 255 is outside standard ASCII. UART carries bits without choosing their character interpretation.