Solenoid Coil Symbol
Definition: The Solenoid Coil symbol represents an electromagnetic actuator coil that converts current into linear mechanical motion of a ferromagnetic plunger, drawn per IEC 60617 as a series of coil humps (three to four semicircular loops) with an arrow indicating the armature/plunger travel, and carrying terminals A1 and A2 per IEC coil-marking convention.
Also known as: solenoid, solenoid coil, electromagnet coil, linear solenoid, plunger solenoid, actuator coil, pull/push solenoid, operating coil.
What the Solenoid Coil symbol means
The solenoid coil symbol denotes a wound electromagnet whose purpose is motion: energising the coil creates a magnetic field that pulls a movable iron plunger (armature) into the coil bore, and that stroke does mechanical work — opening a valve, throwing a latch, engaging a starter pinion, striking a chime bar. It is distinct in intent from the inductor (same physical construction, but used for its electrical inductance) and from the relay/contactor coil (an electromagnet whose only job is to move its own contacts). The plunger arrow in the symbol is what signals 'this coil moves something'.
The terminals A1 and A2 follow IEC 60445/EN 50005 coil-marking practice, shared with relay and contactor coils: control drawings wire A1 toward the switched supply and A2 toward the return, though a plain solenoid coil is not polarity-sensitive unless it contains a built-in diode or is a polarised/latching type. In ladder diagrams the solenoid is a classic output element — the last thing on the rung, turning electrical logic into physical action.
How to identify the Solenoid Coil symbol
IEC-style drawings show the actuator winding as a run of three or four semicircular humps (the same loops as an inductor) with a straight lead at each end, plus an arrow — either through the coil or alongside it — representing the plunger and its direction of travel; a small T-bar or block on the arrow sometimes depicts the armature. In industrial/ladder practice the operating coil is often abstracted to a rectangle (IEC) or a circle with a designation like 'SOL' (NEMA/JIC ladder diagrams), and pneumatic/hydraulic drawings per ISO 1219 show the solenoid as a small rectangle with a diagonal line attached to the valve box it actuates.
Separate it from the plain inductor (humps but no plunger arrow, and often a core line for iron-core chokes), from the relay coil (rectangle whose dashed link goes to contact symbols, not to a mechanism), and from the solenoid valve symbol (which combines this coil with a valve body).
Live editor identity: Live-library identity: `solenoid-coil`, 60 × 28 canvas units, 2 logical terminals. Match this exact SVG and terminal list when identifying the placeable editor symbol; do not identify a physical package from the schematic outline alone.
Function and usage boundary
Current through the winding magnetises the steel frame and plunger; the plunger is pulled toward the position of minimum magnetic reluctance — into the coil — compressing or extending against a return spring. Force is greatest at the fully seated position and falls off steeply with air gap, which is why solenoids are short-stroke devices (millimetres) and why datasheets publish force-versus-stroke curves. De-energise and the spring returns the plunger; in a latching solenoid a permanent magnet holds position with zero power and a reverse pulse releases it.
Electrically the coil is a substantial inductance with low DC resistance. Two consequences dominate design: at turn-off the collapsing field generates a large inverse voltage spike, so DC solenoids need a flyback diode (or RC/TVS snubber) across A1–A2 to protect the driving transistor or switch contacts; and AC solenoids draw a large inrush current while the plunger is out (high reluctance, low impedance) that falls to a much smaller holding current once seated — a stuck AC plunger therefore overheats the coil quickly. Duty cycle ratings (continuous vs intermittent, e.g. 25% ED) limit how long the coil may stay energised without overheating.
Usage boundary: Use the Solenoid Coil abstraction only when the intended circuit can be expressed through these logical ports: `a` (A1), `b` (A2). Select a versioned physical profile and exact manufacturer datasheet before assigning package pins, ratings, or fabrication dimensions.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 draws windings as semicircular humps or a rectangle for operating coils, with mechanical-function arrows per its general rules; IEC 60445 defines the A1/A2 coil terminal markings; solenoid-operated valve actuators in fluid-power schematics follow ISO 1219-1. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 shows coil windings as loops or a circle/rectangle coil element; NEMA ICS and JIC ladder-diagram practice labels output coils 'SOL' with a device number; NFPA/ANSI fluid-power drawings mirror ISO 1219 solenoid actuator boxes. |
| Key difference | IEC leans on the humps-plus-arrow or rectangle form with A1/A2 markings; North American ladder diagrams abstract the solenoid to a circle marked SOL. Fluid-power symbols are internationally harmonised through ISO 1219, so a solenoid-actuated valve looks the same worldwide. In every convention the giveaway distinguishing a solenoid from an inductor is the mechanical actuation mark, not the winding itself. |
The displayed SVG is the live editor implementation, not a licensed reproduction or certification of an IEC or IEEE database glyph. Verify the exact official entry and project edition before issuing work.
Variant availability
- Editor implementation (available): This is the exact SVG and terminal geometry placed by the CircuitDiagramMaker editor.
- IEC 60617 (reference only): IEC 60617 is the official international source. This page does not present the editor SVG as a licensed or certified IEC reproduction.
- ANSI/IEEE 315 (reference only): IEEE 315 is the North American reference listed by IEEE as inactive-reserved; use the edition required by the project.
Logical terminals
The live editor exposes `a` (A1), `b` (A2). These are stable logical terminal IDs for diagram connectivity, not a promise that they equal physical package pin numbers.
| Logical ID | Editor terminal name |
|---|---|
| a | A1 |
| b | A2 |
Polarity and direction
This editor symbol does not encode a universal positive/negative orientation. Do not infer physical polarity or package pin numbering from left/right placement alone.
Reference designator
Project-defined: No single reference letter is asserted for this broad symbol. Apply the project standard and equipment-classification rules consistently.
Where the Solenoid Coil symbol is used
- Solenoid valves controlling water, air, fuel and refrigerant in irrigation, washing machines, pneumatics and HVAC
- Electric door strikes, cabinet locks and vending-machine latches releasing on command
- Automotive systems: starter-motor engagement solenoids, transmission shift solenoids and fuel shut-offs
- Pinball machines, chimes and printers, where solenoids fire flippers, strike bars and actuate paper paths
- Industrial automation: part diverters, brakes, clutches and interlock pins driven from PLC outputs
- Ladder-logic output devices (marked SOL) actuating pneumatic 3/2 and 5/2 valves in machine control
Key facts
- The symbol is a coil winding (3–4 humps or a rectangle) plus a plunger/actuation arrow — the arrow is what distinguishes a solenoid from a plain inductor.
- Terminals are marked A1 and A2 per IEC 60445, the same convention as relay and contactor operating coils.
- A solenoid converts current to short linear strokes (typically 2–10 mm); pull force rises steeply as the plunger seats, so force is always quoted against stroke.
- DC solenoids demand a flyback diode or snubber across the coil — the turn-off inductive spike can reach hundreds of volts and destroys drive transistors and switch contacts.
- AC solenoids draw 2–10× inrush current until the plunger seats; a jammed plunger keeps the coil in inrush and burns it out in minutes.
- Duty cycle matters: intermittent-rated coils (e.g. 25% ED) overheat if held energised; continuous-rated coils run cooler but pull less force per watt.
- Return is by spring (or a permanent magnet in latching types, which hold position at zero power and release on a reverse pulse).
- In NEMA/JIC ladder diagrams the solenoid appears as an output coil labelled SOL; in ISO 1219 fluid-power drawings it is the small actuator box with a diagonal on the valve envelope.
Common interpretation mistakes
- Treating the Solenoid Coil drawing (60 × 28 canvas units) as a physical footprint. The schematic outline expresses electrical intent; package and panel dimensions come from the selected physical profile.
- Copying `a`, `b` directly to a wire marker or manufacturer package pin number. These are logical Solenoid Coil port IDs and require an exact ordered-part terminal map.
- Assuming every unlabelled or generic Solenoid Coil terminal has the same role across manufacturers and variants.
Frequently asked questions
What is the difference between a solenoid coil and an inductor?
Physically both are wire wound into a coil, and 'solenoid' is even the geometry term for such a winding. The difference is purpose and construction: an inductor exists for its electrical inductance (filtering, energy storage) and has a fixed core, while a solenoid actuator has a movable iron plunger and exists to produce motion. The symbols reflect this — the solenoid adds a plunger/arrow to the winding humps. Treating a solenoid as 'just an inductor' electrically is, however, exactly right for drive design: it stores energy and kicks back at turn-off.
Why does a solenoid need a flyback diode?
The coil is an inductor carrying current; when the driving switch opens, the current cannot stop instantly, so the collapsing field drives the coil voltage to whatever level finds a path — easily hundreds of volts — arcing switch contacts or avalanching a transistor. A diode across A1–A2, reverse-biased in normal operation, gives that current a safe recirculation loop, clamping the spike to about 0.7 V above supply. For faster plunger release, use a diode in series with a Zener or an RC/TVS snubber instead of a bare diode.
What do A1 and A2 mean on a solenoid or coil?
A1 and A2 are the IEC 60445 standard markings for the two ends of an operating coil, used identically on solenoids, relays and contactors. Convention wires A1 toward the switched control supply (e.g. from the PLC output or line) and A2 toward common/neutral, which keeps control drawings consistent and fault-finding predictable. An ordinary solenoid coil is not polarity-sensitive, but versions with built-in flyback diodes, LEDs or electronics are — those must be connected with the marked polarity.
Why did my AC solenoid coil burn out?
Almost certainly a plunger that never seated. An AC solenoid's current is limited by inductive impedance, which is low while the magnetic circuit has an air gap: during the stroke the coil draws 2–10 times its holding current. If dirt, misalignment or a mechanical jam stops the plunger from seating, the coil sits at inrush current continuously and overheats within minutes. Other culprits: wrong voltage, duty cycle exceeded (an intermittent-rated coil held on), or rapid cycling without cooling time.
Can I drive a solenoid directly from an Arduino or logic output?
No — logic pins source tens of milliamps, while even small solenoids draw hundreds of milliamps to amps at 5–24 V. Drive the coil through a logic-level MOSFET (or NPN/Darlington, or a driver IC like the ULN2803 for multiple coils), power it from its own supply rail, always fit the flyback diode across A1–A2, and share only the ground with the microcontroller. For latching solenoids, use an H-bridge so you can pulse current in both directions.
Sources and verification
- IEC 60617:2026 DB — Graphical symbols for diagrams (International Electrotechnical Commission) — The current official IEC graphical-symbol database and the electrotechnical areas it covers. Exact symbol identity data requires IEC access.; claim scope: standards
- IEEE/ANSI 315-1975 — Graphic Symbols for Electrical and Electronics Diagrams (IEEE Standards Association) — The official catalogue record for North American diagram symbols and reference-designation letters; IEEE lists the standard as inactive-reserved.; claim scope: standards, reference_designator
- IEC 61666:2010+AMD1:2021 — Identification of terminals within a system (International Electrotechnical Commission) — General principles for identifying terminals within systems; it does not replace the exact ordered-device datasheet.
- IEC 81346-2:2019 — Object classes and reference-designation codes (International Electrotechnical Commission) — The official classification scheme used to form reference designations across technical disciplines.; claim scope: reference_designator
- IEC 61082-1:2014 — Preparation of documents used in electrotechnology (International Electrotechnical Commission) — General presentation rules for electrotechnical diagrams, drawings, and tables.; claim scope: standards, usage
Geometry fingerprint: 8f63049bc15b78d4. A changed SVG, canvas size, or terminal definition invalidates the recorded review.
Related symbols
- Buzzer / Audible Alarm symbol
- Contactor Coil symbol
- DC Motor symbol
- Inductor / Coil symbol
- Relay Coil symbol
- Solenoid Valve symbol
Physical breadboard, PCB, and panel mapping
No universal physical profile is published for this symbol yet. Create a versioned custom part from the exact manufacturer dimensions and terminal map before fabrication.
Place the Solenoid Coil symbol directly on a wiring diagram or schematic in the free online editor — no download required.