A-B 1746-QS Setting Up the Hardware Synchronized Axes Control Module

Minimizing Interference

from Radiated Electrical

Noise

Important: Signals in this type of control system are very susceptible to

radiated electrical noise. The module is designed to detect loss-of-sensor

and sensor noise conditions for any of the four axes when position values

are lost or corrupted. The Hydraulic Configurator displays these

conditions in the Status word window. The resulting hard or soft stop

depends on how you configured autostop conditions. (See Hydraulic

Configurator, Config word, and click on autostop “Help“).

To minimize interference from radiated electrical noise with correct

shielding and grounding:

• Connect LDT cable shields and drive output cable shields (all

shields at one end, only) to IFM terminal block SH terminals, and

connect the IFM terminal block GND terminal (51) to earth ground.

• Keep LDT signal cables far from motors or proportional amplifiers.

• Connect all of the following to earth ground:

– power supply cable shields (one end, only)

– LDT flange, frame, and machine

– I/O chassis

– AC ground

• Use shielded twisted pairs for all connections to inputs and outputs.

• Run shielded cables only in low-voltage conduit.

• Place the SLC-500 processor and I/O chassis in a suitable enclosure.

Important: To minimize the adverse effects of ground loops, you must

isolate power supply and signal commons from earth ground as follows:

1. Connect power supply commons to IFM Com terminal (50), and

LDT commons to LDT Com terminals of the IFM terminal block.

Be sure that they are isolated from earth ground.

2. Connect the cable shield of the servo or proportional amplifier

output cable to a zero potential terminal inside the amplifier.

3. Use bond wires that are equal in size to signal wires.

4. When practical, use one power supply to power only your LDTs.

Connecting Outputs to Output Devices

Note: Follow manufacturer recommendations for shielding the output

cables of the proportional amplifier. Typically, pulse-width modulated

outputs radiate electrical noise originating from the +24V dc power

supply, so isolate the shields of the amplifier output cable to a 0V dc

connection inside the proportional amplifier.

You have a choice of three configurations to match your hydraulics:

• proportional amplifier integrated with a proportional valve

• servo amplifier and variable-volume pump or servo valve

• Allen-Bradley 1305 Drive and hydraulic pump

You may use either of the following output voltage ranges:

• 0-10V dc for an Allen-Bradley 1305 Drive or variable-volume pump

• –10 to +10V dc for a proportional or servo amplifier

If using servo valves, you must convert the module’s output from

voltage to current.

Output Polarity

In most hydraulic systems, the actuator extends (with increasing

LDT counts) when a positive voltage is sent to the output. The

extend direction is defined as the direction that causes the LDT to

return increasing counts moving away from the head.

You can make these selections in the Config word that affect output:

• To generate a positive drive output (0-10V dc) regardless of move

direction, you can select Absolute Mode.

• To extend the actuator by sending a negative voltage to the

output, you can select Reverse Drive Mode.

For additional information on the Configuration word, select that

subject in Help Topics.

Checking Out the Wiring and Grounding

Repeat this procedure to check out each of the four axis loops

connected to the IFM terminal block.

ATTENTION: Be sure to remove all power to the SLC processor,

LDT, valve and pump beforehand.

1. Disconnect the LDT connector at the head end.

2. Disconnect the connector to the IFM terminal block.

3. Turn ON the power supplies for the LDT and SLC processor, and

check the LDT connector and IFM terminal block for:

• +15V dc

• PS common

• –15V dc

4. Observe that the module’s fault LED indicates Green.

5. Verify continuity between IFM COM terminal (50) and each of:

• shield of the amplifier output cable to the valve

• output common on