ADLINK PCI-7250/7251 Relay Output Card Selection and Expansion Guide

ADLINK PCI-7250/7251 Relay Output Card Selection and Expansion Guide

Introduction: The Key Role of Industrial I/O Cards in Automation Upgrades

In industrial control systems, relay outputs are used to drive external actuators such as motors, solenoid valves, and alarm lights, while isolated digital inputs are used to collect signals from limit switches, buttons, and sensors. With the transition from PCI bus to PCIe, many older I/O cards are facing discontinuation or compatibility issues. The ADLINK PCI-7250/7251 series offers flexible relay quantity and input channel expansion solutions, and introduces low profile PCI (LPCI-7250) and PCI Express (LPCIe-7250) versions, as well as CompactPCI (cPCI-7252) specifications to accommodate different chassis and bus requirements. This article will comprehensively analyze the engineering deployment points of this series of cards from model comparison, expansion configuration, electrical characteristics, driver installation to typical applications, helping technicians make efficient decisions when replacing old I/O modules or building new projects.

Product model and expansion architecture

2.1 List of Basic Models

PCI-7250: Main card, providing 4 SPDT (Single Pole Double Throw, Form C) and 4 SPST (Single Pole Single Throw, Form A) relay outputs, as well as 8 isolated digital inputs. Adopting standard PCI 2.1 (5V) bus and 37 pin D-sub female interface.

PCI-7251: Expansion card, no bus interface, must be connected to PCI-7250 through a flat cable, providing the same 8-way relays (4 SPDT+4 SPST) and 8-way isolation DI as the main card. One PCI-7250 can connect up to 3 PCI-7251, doubling the total number of channels (up to 32 relays+32 DI).

LPCI-7250: Low profile PCI card (3.3V/5V universal), providing 8 SPDT relays (without dual SPST) and 8 isolated DI, 50 pin SCSI-II interface, suitable for compact chassis.

LPCIe-7250: PCI Express x1 version, with the same specifications as LPCI-7250, compatible with modern motherboards.

CPCI-7252: 3U CompactPCI module (PICMG 2.0), providing 8 SPDT relays and 16 isolated DI (doubled input channels), designed specifically for telecommunications and military grade racks.

2.2 Comparison of Expansion Capability

Model combination relay total SPDT SPST isolation DI

PCI-7250 8 4 4 8

PCI-7250+1×7251 16 8 8 16

PCI-7250+2×7251 24 12 12 24

PCI-7250+3×7251 32 16 16 32

LPCI/LPCIe-7250 8 8 0 8

cPCI-7252 8 8 0 16

Selection tip: If a large number of SPST (normally open only) relays are needed, the PCI-7250 combination is more flexible; If only SPDT (both normally open and normally closed) is needed and space is limited, LPCI-7250 is better.

Relay output characteristics and engineering wiring

3.1 Contact specifications

PCI-7250/7251 and cPCI-7252: AC 120V@0.5A ， DC  24V@1A (Resistive load), operation/release time of about 8ms, mechanical life>5 × 10 ⁵ times (24VDC/1A).

LPCI/LPCIe-7250：DC  30V@2A (Higher current), operating life>10 ⁵ times (2A/30V), but without AC rating, only suitable for DC loads.

Important difference: The LPCI version has a higher rated current for contacts (2A), but the voltage is lower and does not support AC, making it suitable for driving DC solenoid valves or LED indicator lights; The PCI-7250 version supports AC 120V and can drive AC contactors or small motors.

3.2 Relay status indication and readback

Each relay corresponds to an onboard LED (lit to SET status, extinguished to RESET). The software can obtain the current output status by reading the register (relay read back function), avoiding unknown status caused by external power failure or malfunction. This is a more reliable feature than simple latch output.

3.3 Wiring precautions

The relay is a non latch type, which returns to its initial state after power failure (normally open contacts open, normally closed contacts closed).

The voltage resistance between contacts is 1000VRMS, but the high and low voltage signals still need to be routed separately to avoid interference during wiring.

The use of DIN-37D-01 or ACLD-9137-01 terminal blocks facilitates the connection of external devices and supports DIN rail installation.

Isolation digital input characteristics and anti-interference design

4.1 Electrical Parameters

Number of channels: 8 main cards (PCI/LPCI/PCIe); CPCI-7252 has 16 channels.

Input range: 0~24V, non-polar (bridge rectifier inside optocoupler), can be connected to NPN or PNP sensors.

Logical threshold:

High level: 5~24V (PCI/LPCI/PCIe and 7251), 3~24V (cPCI-7252)

Low level: 0~1.5V (former), 0~1V (latter)

Input resistance: 2.2k Ω @ 0.33W (PCI series), 1.2k Ω @ 0.5W (cPCI-7252)

Isolation voltage: 5000VRMS (much higher than general optocouplers), suitable for high common mode interference environments.

4.2 Low pass filtering options

Each DI channel can choose whether to enable RC filtering (hardware jumper or software configuration, see manual for details) to filter out contact jitter and transient noise in industrial sites. After enabling filtering, the response time slightly increases (about a few milliseconds), but the stability is greatly improved.

4.3 Wiring Examples

External dry contacts (such as buttons): One end is connected to DI+(or DI-H/L), and the other end is connected to IGND (isolated ground).