Voltage Sources (Batteries/DC)
Long plate = +, short plate = −. Use on simple DC schematics.
Generic DC supply symbol. Label with voltage (e.g., 5 V, 3.3 V).
Resistors & Passives
US/ANSI style. Label value (e.g., 220 Ω).
International/IEC style used in many datasheets.
Two plates. For ceramic film caps.
Curved negative plate indicates electrolytic; observe polarity.
Inductor & Transformer
Coil symbol. Stores energy in a magnetic field.
Two coils with a core (parallel lines). Step up/down AC.
Diodes & LEDs
Triangle hits a bar → current flows towards the bar direction (→|).
Arrows show light coming out. Use a series resistor.
Bent bar indicates zener knee voltage.
Transistors (BJT Examples)
Arrow on emitter points out (Not Pointing iN = NPN).
Arrow on emitter points in (Pointing iN = PNP).
Switches & Protection
Single Pole Single Throw. Draw closed by connecting the gap.
Protects circuits by melting when current is too high.
Node you can clip to or plug into. Label with signal name.
Power, Ground & Outputs
General light output symbol. Sometimes an LED symbol is used instead.
Three lines decreasing in width. Use for reference/return.
Circle with “M”. For DC motors in beginner diagrams.
Meters
Connect across (parallel) with the part being measured.
Connect in series so current flows through the meter.
Drawing Tips
- Be consistent: Pick either ANSI (zig‑zag resistor) or IEC (rectangle) and stick with it.
- Label values: Show part value (e.g., 10 kΩ), tolerance if needed (±5%), and reference (R1).
- Wires & dots: Use solid dots for connections and hop‑over humps for cross‑overs that don’t connect.
- Left‑to‑right flow: Inputs on the left, outputs on the right; ground at the bottom, supply at the top.
- Units: V, A, Ω, F, H. Use prefixes: m (milli), μ (micro), n (nano), k (kilo), M (mega).
- Title block: Add project name, author, revision, and date for printouts.