Configured for closed-loop hydraulic axis positioning in a ControlLogix chassis, the Allen-Bradley 1756-HYD02 (1756-HYD02 Hydraulic Servo Module) receives LDT position feedback and generates a +/-10 V analog command for hydraulic actuator control. The module provides two-axis control with selectable servo loop rates from 500 Hz to 4 kHz.

Model Identification

The catalog number 1756-HYD02 identifies the ControlLogix hydraulic servo module. Rockwell Automation documentation specifies it as a two-axis LDT hydraulic module with a 36-position field wiring interface. No additional suffix is present in the supplied catalog number.

Hardware Specifications

The published Rockwell Automation specifications confirm the 700 mA at 5.1 VDC and 2.5 mA at 24 VDC backplane loads, 5.5 W maximum power dissipation, 0 to 60 deg C operating range, and 30 V continuous user-to-system isolation.

ControlLogix Motion Interface

The 1756-HYD02 uses LDT feedback to close the hydraulic position loop. The module accepts transducer feedback and produces a +/-10 V analog command reference for the hydraulic actuator or valve.

Key motion parameters include:

• 2 hydraulic servo axes per module.
• Up to 32 controlled axes per ControlLogix controller.
• 500 Hz to 4 kHz selectable loop update rate.
• 230,000 LDT counts absolute position range.
• 16-bit analog output resolution.
• PID control with feed-forward and directional scaling.
• LDT input using PWM or Start/Stop interrogation.
• Optically isolated, current-sinking registration input.

The hydraulic servo module must be installed in the same chassis as the ControlLogix controller that controls it. For distributed motion systems, Rockwell Automation specifies a ControlLogix controller in each chassis containing a servo module.

Backplane and I/O Electrical Interface

The module draws power from the ControlLogix backplane rather than requiring a separate module power input.

• 5.1 VDC backplane current: 700 mA.
• 24 VDC backplane current: 2.5 mA.
• Maximum power dissipation: 5.5 W.
• Analog servo output: +/-10 VDC.
• Analog output resolution: 16 bits.
• Other outputs: solid-state isolated relay contacts.
• Nominal discrete output voltage: 24 VDC.
• User-to-system isolation: 30 V continuous.

Ordering Information

• 1 x Allen-Bradley 1756-HYD02 Hydraulic Servo Module.
• 1 x 36-position field wiring interface is required for field wiring.
• 1 x compatible 1756-TBCH or 1756-TBS6H terminal block when field termination is required.
• The terminal block is a separate accessory and should be specified according to the installation wiring method.

Field Installation Guidelines

Chassis Installation

• Install the module in a compatible 1756 ControlLogix chassis.
• Keep the 1756-HYD02 in the same chassis as its controlling ControlLogix controller.
• Verify available backplane current before adding the module.
• Use the specified 36-position terminal block for field wiring.

LDT Feedback Wiring

• Use an LDT that accepts the required external interrogation signal.
• Do not use a transducer configured for internal interrogation when external synchronization is required by the module.
• Route feedback wiring separately from high-current switching conductors.
• Maintain appropriate signal shielding and grounding practices for low-level feedback circuits.

Analog Output Wiring

• The servo command output operates at +/-10 VDC.
• Keep analog command wiring separated from high-voltage and high-current conductors.
• Avoid unnecessary parallel routing with switching outputs or motor power cables.
• Verify the connected valve or actuator input impedance against the module specifications.

Environmental Conditions

• Operating temperature: 0 to 60 deg C.
• Storage temperature: -40 to 85 deg C.
• Relative humidity: 5 to 95%, non-condensing.
• Operating vibration: 2 g at 10 to 500 Hz.
• Operating shock: 30 g.
• Non-operating shock: 50 g.

Frequently Asked Questions

• How many axes can the 1756-HYD02 control?

  The module supports a maximum of 2 hydraulic servo axes. A ControlLogix controller can support up to 32 axes through multiple compatible motion modules.

• What feedback device does the module use?

  The module uses Linear Displacement Transducer (LDT) feedback. The LDT input supports PWM and Start/Stop rising or falling edge interrogation methods.

• What is the analog servo output range?

  The servo output is an analog voltage signal with a range of +/-10 VDC and a resolution of 16 bits.

• What servo loop rates are available?

  The selectable servo loop rate ranges from 500 Hz to 4 kHz. The selected rate determines the position-loop update frequency.

• What is the backplane current requirement?

  The module requires 700 mA from the 5.1 VDC backplane supply and 2.5 mA from the 24 VDC backplane supply.

• Can the module be installed in a remote chassis?

  The controlling ControlLogix controller must be installed in the same chassis as the 1756-HYD02. Distributed motion requires a controller in each applicable chassis.

• Which terminal blocks are compatible?

  The documented field wiring terminal blocks are 1756-TBCH and 1756-TBS6H, both providing the required 36-position interface.

• What is the operating temperature range?

  The specified operating temperature range is 0 to 60 deg C. Storage temperature is specified from -40 to 85 deg C.