Optical sync vs wired sync
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Cabling cost & interference robustness. This page explains the timing-synchronization methods used by safety light curtains — optical sync (no dedicated sync cable) and wired sync (separate sync conductors). We compare EMI robustness, long-distance behavior, dense-machine layouts, welding/glare scenarios, and provide a simple TCO estimator for cabling and commissioning time.
Quick answer: Optical synchronization can reduce interconnect wiring, but both emitter and receiver still need the connections specified by their design. Wired synchronization does not automatically prevent electrical or optical interference. Compare the exact model’s supported modes, response times and interference-control arrangements, then assess the real cable route and validate each protective field with neighboring equipment operating.
1) Principles: how each method stays in step
The light-curtain series selection guide helps identify a candidate; obtain its wiring manual to confirm which synchronization methods it actually supports. Method choice is a device-specific integration decision.
Optical sync
- Timing information is embedded in the emitted beam pattern; the receiver locks to that pattern.
- Fewer cables: only power + OSSD/EDM; no dedicated sync wire between Tx/Rx.
- Requires clean line-of-sight during lock; cross-talk control is handled by coding and timing offsets.
Wired sync
- Tx/Rx share a hardwired sync pair that dictates scan timing.
- Extra cable/core where the design requires it; check the documented EMC and optical limits independently.
- Long runs benefit from shielded sync pairs and proper grounding.
2) Side-by-side comparison
| Aspect | Optical sync | Wired sync |
|---|---|---|
| Cabling & install time | May remove a dedicated interconnect; power/output cables remain | May need extra conductors or connectors; depends on topology |
| EMI & drives nearby | Optical timing path is not a conducted cable path; electronics and power/output wiring remain exposed | Follow documented cable/shield design; wiring does not guarantee EMI immunity |
| Welding arc / bright glare | Check ambient-light limits and approved shielding | Receiver optics still require a usable optical signal and documented glare tolerance |
| Multiple curtains in close proximity | Use supported scan codes/orientation/separation | Use the supported interference-control topology; wiring alone does not eliminate optical interference |
| Very long range | Respect model-specific optical and accessory limits | Respect optical span and sync-cable limits |
| Serviceability | Use model diagnostics; fewer interconnects may simplify checking | Check permitted diagnostic procedures and wiring; no universal sync-pin waveform |
3) Selection matrix
| Scenario | Recommended sync | Why | Notes |
|---|---|---|---|
| Compact cell, short range, clean optics | Optical where supported | May avoid a dedicated interconnect | Meet reflective-clearance and alignment requirements |
| Press lines with VFDs/servos clustered | Evaluate both documented designs | Cable routing, supply and EMC performance govern suitability | Do not rank immunity from sync method alone |
| Welding booths / bright arcs | Select by documented optical/environmental limits | Both methods need reliable received light | Use approved shielding and verify during the real process |
| Multi-curtain arrays side-by-side | Supported coding or wired control arrangement | Interference prevention is model-specific | Validate every field with neighboring emitters active |
| Retrofit with limited cable routes | Optical if functionally suitable | Potentially one less interconnect to route | Confirm remaining cables, operating mode and response time |
4) Cabling cost & time estimator (TCO)
This estimator is an illustrative installation-cost worksheet; it does not include all lifecycle costs or prove savings. Response time must be taken from the chosen mode: Omron’s F3SG-SR response-time table lists separate optical and wired values. If unexpected trips drive the decision, first follow the alignment and interference investigation.
Enter actual extra cable length for the chosen wiring topology; core count is not cable length.
Model: Material = length × cost/m, Labor = length ÷ rate × labor_cost. Wired adds additional routed length to Material and Labor. Defaults are examples, not quotations. The model assumes equal cable prices and installation rates and excludes sensor/controller prices, terminations, validation and downtime; the delta is not a measured saving.
5) Commissioning checklist
For optical sync
- Verify alignment margin across corners/center; log receiver indicators.
- Check for cross-talk: with other emitters active, verify that each curtain detects its prescribed test piece and reaches its documented safe state.
- Meet reflective-clearance requirements and use approved shielding; record the final geometry.
For wired sync
- Use the manual’s sync diagnostics; electrical measurements require known pin assignments and a qualified safe test procedure.
- Verify the documented sync connections and bonding arrangement; do not assume a universal one-end shield rule.
- Follow equipment-specific cable routing, separation and crossing requirements.
Acceptance log (CSV copy)
Machine/Cell,Sync type,Lens tilt (deg),Align margin (%),Cross-talk check,Sync waveform OK,Notes,Date,By
,,, ,,,,
6) Troubleshooting quick map
| Symptom | Likely cause | Fix |
|---|---|---|
| Random trips near VFD cabinets | Possible supply disturbance or EMI coupling | Identify the path; apply documented routing, bonding and supply requirements |
| Intermittent loss of lock (optical) | Glare, contamination or marginal alignment | Use diagnostics and approved shielding; check reflective clearance and alignment |
| Two adjacent curtains interfere | Unsupported layout or interference-control configuration | Apply the exact model's coding/orientation/wired-control method and test all fields |
| Weld spatter damages window | Thermal particles reaching an unsuitable optical assembly | Fit only an approved spatter guard and repeat the required optical checks |
7) FAQ
Does optical sync reduce response time?
It can change response time on a particular device. For example, Omron lists different optical- and wired-synchronization times for F3SG-SR. Use the maximum ON-to-OFF time for the exact height, connection and operating mode, rather than assuming a universal advantage.
Can I mix sync types across a line?
Independent systems may use different supported synchronization methods, but emitter/receiver compatibility and mutual-interference measures must follow each manual. Validate every protective field while neighboring systems operate.
Which is better for retrofits?
Optical synchronization can eliminate a dedicated interconnect where the selected design supports it; both units still need their specified power and output wiring. Compare the actual routing and functions. Neither synchronization method alone proves immunity to welding glare or conducted electrical noise.