Step 2: Triggering

A trigger is what makes the camera capture. Before choosing a mode, check the line will not outrun the camera: this is the single most common cause of rejected triggers and results that lag the part.

Line rate and timing check

Take the inspection time from Processing time in Live Preview or the Library.

The line

Parts per minute120

Inspection time110 ms

Result

Time between parts500 ms

Camera busy22% of the time

Fastest sustainable rate545 parts/min

Comfortable headroomKeep the image trigger buffer at 0 so any overrun is reported rather than hidden.

Output pulse against the PLC scan

Pulse (ms)

PLC scan (ms)

The pulse spans at least two scans, so it is always seen.

Pulses on OV Spark Pro run from 10 to 60000 ms. Twice the scan time is a conservative rule of thumb for an input that is not latched in hardware.

The four modes

OV Spark Pro offers four modes, and manual triggering stays active alongside whichever one you pick, so you can always force a capture while setting up.

Triggering is Step 2 of the Recipe Editor, so it is set per recipe rather than per camera.

Modes at a glance

Mode	What fires the inspection	Paced by
Manual Trigger	Only the manual button	The camera
Interval	A fixed time interval	The camera
AI Trigger	The camera watches the scene and triggers itself when conditions are met	The camera
External	A hardware trigger, PLC, or HTTP request	The outside world

The first three are internal: the camera decides when to look. External waits to be told.

Which one to use

External is the right answer for most production lines. A part sensor fires as each part arrives, so the capture is tied to the part rather than to a clock. Wire the sensor to pin 10, see Pinouts.

Interval suits continuous processes where there is no discrete part: web inspection, a filled hopper, anything where "every 500 ms" is a more meaningful question than "this part".

AI Trigger removes the sensor entirely. The camera watches for the part to be in position and triggers itself. It is useful where mounting a sensor is impractical, at the cost of the camera continuously evaluating frames.

Manual Trigger is for setup, validation and bench work, not production.

When you choose External, tick the sources the recipe should listen to under Enabled sources: GPIO (a sensor wired to the camera), PLC / Fieldbus, or HTTP (a POST /trigger call from your software, see HTTP API). You can tick more than one. A source that is not ticked is ignored, even if something is sending to it.

AI Trigger in practice

AI Trigger uses an Alignment tool as its evaluator. The camera triggers when that tool finds the part, so the aligner's confidence threshold is also the trigger's sensitivity.

Setting	Behaviour
AI evaluator tool	Which alignment tool decides that the part is present
Trigger hold	How long the trigger stays asserted, defaulting to 0 ms
Max checks per second	How often the camera evaluates, defaulting to 10 fps

It fires once when alignment succeeds, holds for the configured time, and re-arms once alignment is lost.

You need an aligner first

If the recipe has no alignment tool, AI Trigger cannot be saved. See Alignment.

There is no separate trigger threshold

Tuning the aligner's confidence threshold tunes the trigger with it. If you raise the threshold to make the inspection stricter, you also make the camera less willing to trigger at all.

The image trigger buffer

Below the modes is the image trigger buffer: how many triggered images the camera will hold while an inspection is still processing.

• 0 accepts one inspection at a time, and additional triggers are rejected as busy
• Higher values queue triggers, absorbing short bursts

Queuing trades latency for correctness

A queue keeps the camera busy, but the result no longer corresponds to the part currently in front of your reject gate. If downstream logic assumes one in, one out, leave the buffer at 0 so an overrun is reported rather than silently delayed.

An overrun you can see in Diagnostic Logs is a problem you can fix. A silently delayed result is a problem you discover from a customer.

Wiring an external trigger

The trigger input is pin 10, referenced to Digital GND on pin 9.

Sensor types and the full circuit are on the Pinouts page. Once wired, use the I/O Live Monitor to confirm the edge is actually arriving before you go looking for problems in the recipe.

Troubleshooting

Symptom	Where to look
No inspection at all	I/O Live Monitor: is there an edge on the trigger track?
"Trigger while busy" in the logs	The line is faster than the inspection. See Diagnostic Logs
"Trigger not ready"	The PLC is triggering before the camera is armed. Check the handshake in Industrial Ethernet
Results lag the part	The trigger buffer is queuing. Set it to 0

Step 6 of 13

← PreviousStep 1: Imaging

Next →Step 3a: Set up alignment tool

Add it as the first tool for the AI to dynamically track the part. Skip only if a fixture holds the part identically every cycle.