OPTO 22 SNAP-PAC Series Modules: SNAP-PAC-S1

Technical Dossier

Product Details And Specifications

OPTO 22 SNAP-PAC Series: Comprehensive Module Range and Technical Overview

The OPTO 22 SNAP-PAC series is a family of programmable automation controllers (PACs) and associated I/O modules deployed across global heavy industry, including petrochemical refineries, nuclear power generation facilities, offshore platforms, water treatment plants, and continuous-process chemical manufacturing. The SNAP-PAC architecture integrates real-time control, deterministic I/O scanning, and Ethernet-based communications into a single unified platform, making it a reference standard for facilities requiring long-lifecycle automation infrastructure. Its modular backplane design allows field-replaceable I/O without controller downtime, a critical requirement in 24/7 process environments. SNAP-PAC controllers run OPTO 22's PAC Control and PAC Display software suites, and the series supports both standalone and distributed control topologies. Installed base density is highest in North American and European process industries, with significant deployment in Asia-Pacific LNG and refining sectors.

The Evolution of SNAP-PAC Architecture

The SNAP-PAC series succeeded OPTO 22's earlier SNAP Ultimate and SNAP Ethernet I/O platforms, which used a separate controller-plus-brain architecture. The SNAP-PAC line consolidated control intelligence directly into the controller module, eliminating the need for a separate SNAP Ethernet Brain on standalone racks. Early SNAP-PAC controllers (circa 2004–2008) operated on 10/100 Ethernet and supported serial legacy protocols including Modbus RTU and DNP3. Mid-generation revisions introduced dual Ethernet ports for network redundancy and expanded memory capacity to support larger PAC Control strategy files. The SNAP-PAC-S1 and SNAP-PAC-S2 represent the standalone controller tier, while the SNAP-PAC-R1 and SNAP-PAC-R2 serve as rack-mounted variants designed for SNAP-PAC mounting racks. The SNAP-PAC-EB1 and SNAP-PAC-EB2 Ethernet brains extend I/O to remote racks without a local controller. As of 2020, OPTO 22 introduced the groov EPIC (GRV-EPIC-PR1) as the next-generation successor platform, offering Linux-based edge computing, Node-RED integration, and OPC UA native support. Facilities running SNAP-PAC hardware face a compatibility boundary: groov EPIC does not share the same backplane or I/O modules, requiring a full rack migration rather than a drop-in upgrade. This architectural discontinuity has extended the active service life of SNAP-PAC installations, as many operators defer migration due to capital cost and process risk.

SNAP-PAC Full Catalog & Functionalities (SKU List)

Controllers — Standalone

• SNAP-PAC-S1: Standalone PAC, single Ethernet port, 256 MB RAM, USB programming port, supports up to 512 I/O points on local rack.
• SNAP-PAC-S2: Standalone PAC, dual Ethernet ports, 512 MB RAM, enhanced strategy file capacity, supports redundant network topologies.

Controllers — Rack-Mounted

• SNAP-PAC-R1: Rack-mounted PAC controller, single Ethernet, mounts in SNAP-PAC-RCK4/RCK8/RCK16 racks, local I/O only.
• SNAP-PAC-R2: Rack-mounted PAC controller, dual Ethernet, expanded memory, supports peer-to-peer communication with other SNAP-PAC units.

Ethernet Brains (Remote I/O Expansion)

• SNAP-PAC-EB1: Single-port Ethernet brain for remote SNAP-PAC racks; controlled by a SNAP-PAC-S or R series controller.
• SNAP-PAC-EB2: Dual-port Ethernet brain for remote racks; supports daisy-chain and star network topologies.

Analog Input Modules

• SNAP-AIMA-4: 4-channel analog input, 4–20 mA, 16-bit resolution, field-configurable range.
• SNAP-AIV-4: 4-channel analog voltage input, ±10 VDC, 16-bit resolution.
• SNAP-AITM-2: 2-channel thermocouple input module, supports J, K, T, E, R, S, B types.
• SNAP-AIRTD-8: 8-channel RTD input, supports PT100/PT1000, 3-wire configuration.

Analog Output Modules

• SNAP-AOMA-4: 4-channel analog current output, 4–20 mA, 16-bit DAC, loop-powered.
• SNAP-AOV-5: 4-channel analog voltage output, 0–10 VDC / ±10 VDC selectable.

Digital Input Modules

• SNAP-IDC5: 4-channel DC digital input, 5–28 VDC, optically isolated, 1 ms response time.
• SNAP-IAC5A: 4-channel AC digital input, 85–250 VAC, optically isolated.

Digital Output Modules

• SNAP-ODC5SRC: 4-channel DC sourcing digital output, 5–28 VDC, 0.5 A per channel, solid-state.
• SNAP-OAC5A: 4-channel AC digital output, 24–280 VAC, solid-state relay, zero-crossing switching.

Communication & Serial Modules

• SNAP-SCM-232: RS-232 serial communication module, supports Modbus RTU master/slave, ASCII protocols.
• SNAP-SCM-485-422: RS-485/RS-422 serial module, multi-drop bus support, up to 32 nodes.

Power Supplies

• SNAP-PS5: 5 VDC rack power supply, 3 A output, mounts in SNAP-PAC rack power slot.
• SNAP-PS24: 24 VDC auxiliary power supply module for field device power distribution.

Mounting Racks

• SNAP-PAC-RCK4: 4-slot SNAP-PAC mounting rack, DIN-rail or panel mount.
• SNAP-PAC-RCK8: 8-slot SNAP-PAC mounting rack.
• SNAP-PAC-RCK16: 16-slot SNAP-PAC mounting rack, maximum I/O density per rack.

Sourcing Hard-to-Find & Obsolete SNAP-PAC Parts

As OPTO 22 transitions its product roadmap toward the groov EPIC platform, a growing subset of SNAP-PAC modules has entered end-of-life or limited-availability status. Modules such as the SNAP-SCM-232, SNAP-AIRTD-8, and earlier SNAP-PAC-R1 controller revisions are no longer in active production, creating sourcing gaps for facilities operating under long-term maintenance contracts or regulatory frameworks that prohibit unvalidated hardware substitutions (e.g., SIL-rated loops, nuclear QA programs).

DriveKNMS maintains a dedicated inventory of tested SNAP-PAC surplus and refurbished modules sourced from decommissioned plant assets, authorized distributor overstock, and controlled secondary market channels. Each unit is catalogued by firmware revision and hardware revision code where applicable, enabling compatibility verification against the customer's existing rack configuration. For facilities requiring multi-year spare parts coverage, DriveKNMS can structure blanket purchase agreements with reserved inventory allocation, reducing exposure to spot-market price volatility for discontinued part numbers.

Quality Control for the SNAP-PAC Range

SNAP-PAC modules present specific test challenges due to their integrated backplane bus architecture and Ethernet-dependent I/O scanning. DriveKNMS applies the following verification protocol to all SNAP-PAC inventory prior to dispatch:

• Backplane continuity test: Each module is seated in a reference SNAP-PAC rack and scanned for correct backplane register mapping. Modules that fail to enumerate correctly are quarantined regardless of visual condition.
• Ethernet brain handshake verification: For EB1/EB2 brains and R-series controllers, a PAC Control strategy is loaded and I/O point read/write cycles are executed across all populated module slots to confirm bus integrity.
• Analog calibration check: All analog input and output modules are tested against NIST-traceable reference signals. Modules with drift exceeding ±0.1% of full scale are recalibrated or rejected.
• Firmware revision logging: Controller firmware version is recorded and disclosed in the shipment documentation. Customers are advised of any firmware delta relative to their installed base to allow pre-deployment update planning.
• Thermal cycling: Modules destined for high-ambient installations (refineries, compressor stations) undergo a 4-hour thermal soak at 55°C prior to final inspection.