Passives (R, L, C)

Passives are the two- and three-terminal parts that resist, store, or divide. de:volt ships the Resistor, the Potentiometer, the Trimmer, the Capacitor (with Ceramic, Electrolytic, and Film variants), and the Inductor. The value is only part of the model: capacitors and inductors also have explicit loss parameters, and identified resistor packages have a compact thermal model.

Resistor

The plainest part in the catalog and the one you place most. A resistor sets a current for a given voltage (I = V / R) or drops a voltage for a given current. It is non-polar: pins a and b are interchangeable.

Pinout

Specs

Change resistance in the Inspector to set the nominal value. The normal transient run uses that nominal value. The tolerance param is the spread used by Monte Carlo analysis; at the 5% default a 220 Ω part can land anywhere from about 209 Ω to 231 Ω across Monte Carlo runs.

For the exact quarter-watt catalog resistor, solved I²R power drives a persistent one-pole body-temperature estimate and an ambient-adjusted continuous-power allowance. Sustained overload accumulates stress and can leave the simulated resistor open for the rest of the session. The thermal network is a teaching approximation: body temperature does not change resistance, and lead parasitics, temperature coefficient, hot spots, airflow, board conduction, and detailed pulse-rating curves are not modelled.

What you use it for

• Current limiting. A resistor in series with an LED caps the current the LED draws. For a red LED on a 5 V rail, a 330 Ω series resistor holds the current to roughly 10 mA: (5 V − 2 V_LED) / 330 Ω ≈ 9 mA. See /parts/leds for the per-colour forward voltages.
• Pull-up / pull-down. A resistor from a floating input to VCC or GND gives it a defined idle level so it isn’t left to pick up noise.
• Voltage division. Two resistors in series tap a fraction of the rail at their midpoint: the basis of every divider on this page.
• Biasing. Setting the quiescent operating point of a transistor or op-amp.

The four-resistor Resistor Array packs four isolated resistors that share one resistance value into a single SIP body: handy for ganged pull-ups on a bus. See /parts/passive-arrays-and-switches.

Potentiometer

A three-terminal variable divider: a resistive track of rTotal with a wiper that taps a point along it. Turning the shaft moves the wiper, so the wiper-to-end resistance varies continuously from 0 to rTotal.

Pinout

Specs

position is where the wiper sits, 0 at the CCW end and 1 at the CW end; 0.5 is mechanical centre. taper chooses how resistance tracks position: linear is proportional, while log is a compact audio-taper mapping. Wiper/contact resistance, scratch noise, bounce, wear, and parasitic capacitance are not modelled.

Wiring it as a divider

Tie one end to VCC and the other to GND, and the wiper delivers a voltage that sweeps the full rail:

VCC ─── CW
         ├── (track) ── W ─── Vout (0 → VCC as you turn)
GND ─── CCW

With CW to VCC and CCW to GND, position = 0.5 puts the wiper at half-rail. Read the wiper on an analog input for a manual knob.

Trimmer

Mechanically the same divider as the potentiometer, but set once with a screwdriver and left alone: for calibration trims you don’t expect a user to touch. There is no taper param; trimmers are linear.

Pinout

Specs

Wire it exactly like a potentiometer: ends to your reference voltages, wiper to the node you’re trimming. The lower p_max reflects the smaller body of a real trimmer.

Capacitor

A capacitor stores charge on two plates; its voltage can’t change instantly, so it smooths, couples, and times. The generic Capacitor part carries a style param that selects the body: and the palette also offers three pre-styled variants so you can grab the right one directly.

Pinout

Specs

The transient model is an ideal capacitance in series with editable esr, plus editable leakageResistance across the terminals. The exact Ceramic, Electrolytic, and Film catalog variants provide different representative defaults. Changing only the generic part’s style changes its body and polarity guidance; it does not invent a new datasheet-grade ESR or leakage curve. Pick the catalog variant that best matches the part you intend to use, then enter datasheet values when they matter.

Ceramic (cap-ceramic)

Default 100 nF, non-polarised, with representative 0.05 Ω ESR and 1 GΩ leakage. Either terminal can sit at the higher voltage. This is the workhorse decoupling cap. Place one close to each IC’s VCC/GND pins so it can supply fast current before the rail sags. The catalog’s tolerance is a Monte Carlo input, not random variation in every transient run.

Electrolytic (cap-electrolytic)

Default 100 µF, POLARISED, with representative 0.2 Ω ESR and 1 MΩ leakage. Pin a is positive (+) and pin b is negative (−). On real hardware, reverse polarity can damage the capacitor. The simulator shows polarity guidance but does not model reverse-polarity damage or breakdown. Use this variant for bulk rail filtering and for large timing values.

Film (cap-film)

Default 1 µF, non-polarised, with representative 0.1 Ω ESR and 1 GΩ leakage. Reach for it in audio coupling, snubbers, and timing work where a film part is a closer hardware match than a generic ceramic.

All capacitor variants omit lead inductance (ESL), dielectric absorption, voltage coefficient, frequency- and temperature-dependent ESR, detailed leakage curves, and breakdown. With ESR enabled, the Inspector does not claim internal capacitor energy from terminal voltage because the voltage across the ideal capacitance is not separately exposed.

Inductor

The dual of the capacitor: it stores energy in a magnetic field and its current can’t change instantly, so it resists changes in current. Non-polar, pins a and b.

Pinout

Specs

Inductors show up in filtering, switching converters, and tuned LC circuits. The simulator places dcr in series with the ideal inductance and coreLossResistance across the terminals. These losses limit current and dissipate power, but they are fixed lumped values rather than frequency-dependent curves. Switching off current can produce a voltage spike, which is why inductive loads need a freewheeling path (see /parts/diodes).

Core saturation, nonlinear permeability, hysteresis, skin effect, parasitic capacitance, magnetic coupling, and heating are not modelled. With the core-loss shunt enabled, the Inspector does not claim magnetic energy from total terminal current because that current also contains the shunt-loss component.

Model identity matters

Exact catalog IDs supply the defaults described above. Older or custom components without a matching ID keep their explicit authored parameters and use labelled generic fallbacks; the engine does not silently guess a package from kind alone. Select a component to see Model identity, Included, and Not included in the Inspector.

Placement

All of these are through-hole and breadboard-friendly. Straddle the centre gap or sit them in a single rail group as the circuit needs; the three-terminal pot and trimmer want their three pins on separate tie-points. See /user/breadboard-mode for how rows and rails connect.