Industrial Engineer · phase 3 of 16 · noun

One-Shot / Edge Detection

Instruction that becomes true for one execution when a Boolean signal changes state.

The Explain card

Plain English: A one shot fires for exactly one scan when its input changes state. Rising edge catches the moment it turns on, falling edge catches the moment it turns off.
Example: A counter must count one part per pulse. Without a one shot, a sensor that stays on for ten scans counts ten parts, so the sensor feeds a one shot and the one shot feeds the counter.
Why it matters: Anything that should happen once per event, like incrementing, toggling or latching an alarm, needs an edge. Forgetting it produces counts that run away and toggles that flicker.
Hook: Catch the moment, then let it go.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

In the conveyor PLC, a One-Shot instruction prevents the part counter from incrementing repeatedly while the photoeye remains blocked.

How it is built

Where it came from

Origin: English compound of one and shot; shot developed from shoot, from Old English scēotan
Entered the language: 20th century
What changed: The compound first described a single attempt or use, then entered electronics and industrial control vocabulary for event-based logic.

How it is spelled

Pattern: A hyphen joins two independent English words into one compound noun.
Pattern: The spelling retains the silent final e in one.

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

PLC event instructions

signal transitions

Phase 3: PLC Program Organization and Execution

How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.