ALLIED AT Series Modules | AT-PWR4 Power Supply

Technical Dossier

Product Details And Specifications

ALLIED AT Series: Comprehensive Module Range and Technical Overview

The ALLIED AT Series represents a widely deployed platform across global heavy industry, with documented installations in petrochemical refineries, chemical processing plants, nuclear auxiliary systems, and offshore oil & gas facilities. The AT Series was engineered to meet the rigorous demands of continuous-process environments where unplanned downtime carries direct financial and safety consequences. Its modular backplane architecture allows field-replaceable I/O, power, and communication modules without full system shutdown, a critical operational requirement in facilities operating under 24/7 production mandates. The AT-PWR4 power supply module is one of the most frequently sourced components in this series, providing regulated DC bus power to the backplane and downstream I/O modules.

The Evolution of AT Series Architecture

The ALLIED AT Series was introduced as part of ALLIED's transition from relay-logic panel systems to solid-state programmable control platforms. Early AT Series hardware relied on parallel backplane communication with fixed-slot addressing, limiting configuration flexibility. Mid-generation revisions introduced enhanced noise immunity on the I/O bus, extended operating temperature ranges, and improved power supply redundancy options — directly responding to field failures reported in high-vibration and high-EMI industrial environments.

As the platform matured, ALLIED introduced firmware-level diagnostics accessible via the front-panel LED arrays and, in later revisions, via RS-232 and RS-485 serial interfaces. The AT Series is now considered a mature/end-of-life platform. ALLIED has transitioned its current installed base toward successor architectures, but the AT Series remains in active service at thousands of sites globally due to the high cost and complexity of full DCS migration projects. This lifecycle status makes reliable spare parts sourcing — particularly for power supply and CPU modules — a primary operational concern for maintenance engineers.

AT Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified components within the ALLIED AT Series platform, organized by functional category. Each entry reflects the module's primary role within the system architecture.

Power Supply Modules

• AT-PWR4: 24VDC regulated backplane power supply, 4A output, single-slot form factor
• AT-PWR8: 24VDC regulated backplane power supply, 8A output, dual-slot form factor
• AT-PWRR: Redundant power supply module, hot-swap capable, for high-availability configurations

CPU / Controller Modules

• AT-CPU1: Base processor module, 16KB user memory, supports ladder logic execution
• AT-CPU2: Enhanced processor module, 64KB user memory, extended instruction set
• AT-CPU3: High-performance CPU, 256KB memory, supports structured text and function block programming
• AT-CPU3E: AT-CPU3 variant with integrated Ethernet port for SCADA connectivity

Digital Input (DI) Modules

• AT-DI16A: 16-channel 120VAC digital input module, optically isolated
• AT-DI16D: 16-channel 24VDC digital input module, sink/source configurable
• AT-DI32D: 32-channel 24VDC digital input module, high-density, dual-connector

Digital Output (DO) Modules

• AT-DO16R: 16-channel relay output module, 2A per channel, Form C contacts
• AT-DO16T: 16-channel transistor output module, 24VDC, 0.5A per channel, sourcing
• AT-DO32T: 32-channel transistor output module, 24VDC, high-density

Analog Input (AI) Modules

• AT-AI8V: 8-channel analog input, 0–10VDC, 12-bit resolution, single-ended
• AT-AI8I: 8-channel analog input, 4–20mA, 12-bit resolution, loop-powered compatible
• AT-AI4T: 4-channel thermocouple input module, supports J, K, T, E type sensors

Analog Output (AO) Modules

• AT-AO4V: 4-channel analog output, 0–10VDC, 12-bit resolution
• AT-AO4I: 4-channel analog output, 4–20mA, 12-bit resolution, short-circuit protected

Communication Adapter Modules

• AT-COMM-RS: RS-232/RS-485 serial communication adapter, Modbus RTU master/slave
• AT-COMM-ETH: Ethernet TCP/IP communication module, Modbus TCP, 10/100 Mbps
• AT-COMM-PB: PROFIBUS-DP slave adapter, up to 12Mbps, GSD file supported

Sourcing Hard-to-Find & Obsolete AT Series Parts

The ALLIED AT Series has entered end-of-life status with the OEM, meaning factory new stock is no longer available through standard distribution channels. DriveKNMS maintains a dedicated inventory of tested surplus, refurbished, and new-old-stock (NOS) AT Series components sourced through verified industrial surplus networks globally.

For maintenance engineers managing aging AT Series installations, DriveKNMS provides the following lifecycle support services: direct SKU cross-reference lookup, functional equivalency assessment for discontinued modules, and emergency same-day dispatch for critical spares. The AT-PWR4 and AT-CPU series modules are among the highest-demand items in our AT Series inventory due to their role as single points of failure in the backplane architecture. Customers operating facilities with no planned migration timeline within the next 5–10 years are advised to establish a buffer stock agreement to mitigate lead-time risk on these critical modules.

Quality Control for the AT Series Range

All AT Series modules processed by DriveKNMS undergo a structured multi-stage inspection protocol before dispatch. Power supply modules including the AT-PWR4 are bench-tested under load conditions at rated output current, with output voltage stability, ripple, and thermal performance verified against OEM specifications. CPU modules are tested with a validated AT Series backplane fixture, executing a standardized ladder logic test program to confirm memory integrity, I/O bus communication, and instruction execution accuracy.

Digital and analog I/O modules are tested channel-by-channel using calibrated signal sources and measurement equipment. Communication adapter modules are validated for protocol compliance using Modbus and PROFIBUS test masters. All modules are inspected for capacitor condition, connector integrity, and PCB corrosion before being classified as serviceable stock. Modules that do not pass functional testing are quarantined and not offered for sale.