Open end trigger cable wiring for optocoupler trigger and strobe

An open end trigger cable is a plug shell, a set of flying leads and your own crimping: the camera side is fixed, and every connection from there to the PLC terminal is yours. Wire the two live circuits correctly — the optocoupled trigger input and the open-drain strobe output — and the camera fires on every part and flashes the light in step with the exposure. This guide gives the pin assignment for the 6-pin and 12-pin plugs, the voltage and current figures that must hold, the resistor arithmetic worked through, and a bench procedure that proves both loops before the cabinet closes.

What you need

• The mating plug: a Hirose HR10A-7P-6S(73) for the 6-pin camera connector, an HR10A-10P-12S(73) for the 12-pin.
• Shielded multi-core cable. The signal cores carry milliamps, so 0.2 mm² (24 AWG) is ample; use 0.5 mm² for the camera power pair, which keeps the round-trip drop about 0.14 V at 0.4 A over a 5 m run and protects the 11–13 V power window.
• A soldering iron or the crimp contacts the plug family specifies, plus heat-shrink and the backshell with its strain relief.
• A current-limited bench supply, a multimeter and, ideally, a scope.
• The camera's I/O controls in your capture software: the trigger source selector and the strobe or line-output enable.

The trigger cable carries signals only — images still travel on the data line between camera and host. For how far a GigE-class run holds up and which cable grade to pick, see 5GBASE-T camera interface: bandwidth, cables and distance. If the pulse comes from a bench generator rather than a PLC, camera trigger cable selection for a signal generator matches levels and connectors before you build the lead.

Pin assignment for the 6-pin and 12-pin plugs

The scheme below is the published assignment used across a common family of machine-vision cameras, and these I/O connectors appear on many GigE area scan cameras. The signal types repeat across the industry — an isolated optocoupler input, an open-drain output, two separate grounds — but pin numbers and lead colours move between camera models, so keep your camera's own I/O sheet beside this table if its connector is not one of the two shown.

6-pin plug, Hirose HR10A-7P-6S(73):

12-pin plug, Hirose HR10A-10P-12S(73):

On the 12-pin plug, four pins carry trigger and strobe, and the published instruction for the remaining pins is to leave them unused.

The trigger input: an LED, and it needs current

Pins 2 and 3 (11 and 12 on the 12-pin plug) are the input side of an optocoupler — an LED looking at your signal. Current has to flow from (+) to (-), the applied voltage must stay inside the window printed in the table, and the source must deliver at least 3.5 mA. Below that threshold the LED never reaches its operating point and the camera sees no edge at all. Reversed leads read the same way: a dead input, not an error message.

Isolation is the point of the optocoupler, so your trigger source shares no ground with the camera. A push-pull output anywhere in that window drives the pair directly, no extra parts needed. When the source is an open-collector sensor or a transistor stage, set the current with one resistor:

Here V_drive is the trigger supply voltage, V_f is the optocoupler LED forward drop — about 1.2 V is typical for a standard optocoupler input — and I is the current you are designing for.

The classic failure is a pull-up sized for logic instead of for an LED. Drive the pair from 3.3 V through 10 kΩ and the current is I = (3.3 − 1.2) V / 10,000 Ω = 0.21 mA, barely six percent of the minimum — the LED never conducts, and everyone blames the software. If you are building the drive stage from scratch, these optocoupler trigger circuits with relay loads run the same current-first arithmetic on a different load.

Optocouplers also add a few microseconds of edge delay that a plain wire does not. It is invisible at part-per-second rates, but it belongs in the timing budget when the trigger has to compensate for a sensor mounted upstream of the camera; camera trigger delay timing for offset inspection sensors works that side out.

The strobe output: a switch to ground, not a source

Pin 4 (pin 10 on the 12-pin plug) is an open-drain transistor. When the camera asserts it, the pin conducts to ground; the rest of the time it floats. It never pushes voltage out, so you supply both the voltage and the load: from the positive terminal of a strobe supply, through the load — pull-up resistor, PLC input, relay coil — into pin 4, with that supply's return landed on pin 5 (pin 7 on the 12-pin plug). Hold both within the output's ratings in the table.

The load sets the current, so the load sets the floor on its own resistance. At the strobe limit the load must be 24 V / 0.2 A = 120 Ω or more; at 12 V, 60 Ω. Controller inputs need almost nothing: a 4.7 kΩ pull-up to 12 V draws I = 12 V / 4700 Ω = 2.6 mA and dissipates 12 V × 2.6 mA ≈ 31 mW while the camera conducts. A small relay coil above 120 Ω fits the budget; a contactor coil or an incandescent lamp does not.

Mind the idle state. With a pull-up fitted, the line rests high at your supply voltage and falls to near 0 V for the duration of the strobe window, so the pulse reads active low. A controller that wants active high is fixed in its input settings or by switching the strobe polarity in the camera's I/O controls, not by rewiring.

To drive the light itself from the camera rather than a generic output, smart camera strobe output: enable it and wire the light covers the enable side, and this GPIO strobe wiring example driven by the exposure-active signal shows the same idea built out end to end. Inductive loads — relay coils, solenoids — get a flyback diode across the coil, because a 0.2 A switch has no tolerance for inductive kick.

Keep the two grounds apart

Pin 5 and pin 6 exist separately on purpose. Pin 6 is the return for the camera's own supply; pin 5 is the return for strobe currents — fast edges, up to 0.2 A, routed right beside your signal wiring. Land them on separate terminals and let them meet only at the supply's star point if they share a source. Daisy-chaining the strobe return through the power ground injects every strobe edge into the camera's supply reference, which shows up as trigger jitter and noise no filter quite removes. Camera GPIO wiring: prevent damage and triage power faults covers what happens when shared returns graduate from noise to damage.

Assemble and prove it out

1. Slide the shell, backshell and heat-shrink onto the cable before any soldering. Then solder or crimp each core into its cavity per the tables above, treating the colour column as a convention rather than a law.
2. Meter every pin to its lead for continuity, then pin to pin for shorts, with the camera unplugged. A short between pins 5 and 6 is the one that bites later.
3. Power the camera: 12.0 V between pins 1 and 6, current-limited, inside the 11–13 V window.
4. Set the trigger source in software to the physical input line, then pulse pins 2 and 3 with 5 V from the bench supply — the input takes its whole rated window directly, so no resistor is needed for this test. One pulse, one frame; ten pulses, ten frames.
5. Wire the strobe pull-up and watch pin 4 with a meter or scope while you enable the output tied to exposure in the I/O controls. The line should drop low for exactly the strobe window and no longer.
6. Nothing firing? Swap pins 2 and 3 and retest; a reversed optocoupler masquerades as a dead input. Frames landing on the wrong edge? Change the trigger activation setting in software, not the wiring.

From there the questions move from wiring to timing. Trigger call versus exposure time: understand capture timing explains the gap between the pulse and the photons, and once two cameras share one part-detect signal, multi-camera exposure synchronization with a shared trigger is the next problem up.

Mistakes that cost an afternoon

• Treating the strobe as a voltage source. It only pulls to ground; with no pull-up and no return on pin 5, flawless-looking wiring reads dead on a meter.
• Logic-sized pull-ups on the trigger input. If the source cannot deliver 3.5 mA, the camera ignores the edge — size for 10 mA and stop revisiting it.
• One ground for everything. Power return and strobe return sharing a conductor puts every strobe edge on the camera's supply reference.
• Asking the strobe pin for more than its 0.2 A ceiling. Relay coils and controller inputs fit; lamps, brakes and contactors do not.
• Blaming the trigger when the data link is down. The trigger pair moves no pixels; if the camera has power but no image on the host, camera has power but not detected: USB link checks after a cable swap is the faster path.

Moulded cables that skip the soldering

For a permanent loom, a moulded cable from the cables category lands the same power and I/O functions on open ends, with factory-crimped contacts and tested continuity. This line's camera-side connector is the 8-pin M8 type on a drag-chain rated jacket:

Cameras with the 12-pin I/O connector have a moulded equivalent carrying I/O and power on 12-pin conductors. The trigger pair never carries images, so budget a data cable alongside it: the LS-CBL-0117 is an RJ45 camera data cable with locking studs over 15 m, and the LS-CBL-0199 is a 3 m high-flex GigE cable built for drag chains.

From bare leads to a running line

The whole build is an hour at the bench: a plug, a meter and one resistor per circuit — 2.2 kΩ in series with the trigger pair fed from the PLC rail, 4.7 kΩ pulling the strobe up to 12 V. Once both loops pulse cleanly, the loom disappears into the machine and stays there. To pick cable and camera as one order, start at the extras step of the configurator, filter power and I/O cables by length in the accessories finder, or match the camera itself in the camera finder. The contact page reaches the applications team when your camera's I/O connector matches neither plug in the tables above.