MachPro TP400 Probe Wiring to M31 Motion Controller

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How-to guide

Scope

This procedure shows how to wireWire a TP400 touch probe to an M31 motionDI controller(Digital digitalInput). input. It also shows where to connectConfigure the cableTP400 shield.output as NO or NC by swapping the TP400 power wire polarity.

TermsDefinitions

• 0 V DC: The DC power(Direct returnCurrent): conductorElectrical forcurrent athat 24flows Vin DCone supply.direction.

• PEDI (ProtectiveDigital Earth)Input): TheAn safetyon/off earthinput bond foron the enclosure and bonded devices.M31.

• Chassis ground: The metal enclosure bond point. Chassis ground is bonded to PE.

• PNP (sourcing) input: A digitalAn input that turns ON when itthe receivesDI terminal is driven to +24 V DCVDC relative to 0 VVDC.

  DC.

• NO (Normally Open): Output is open when the probe is not triggered.

• NC (Normally Closed): Output is closed when the probe is not triggered.

• PE (Protective Earth): Safety ground bonded to the enclosure.

PrerequisitesElectrical requirements

• ATP400 regulatedinput power: 24 VVDC DC power supply for field I/O.±10%.

• ATP400 freeoutput load current limit: 50 mA max.

• M31 digitalDI: input16 configuredinputs as(PNP asourcing), 16–2

Wire colors (manufacturer)

• Red: Probe power lead (polarity depends on NO/NC selection)

• Green: Probe 

• Blue: Probe status output lead

• Black: Probe status output lead
  The TP400 can reverse output logic by changing the power polarity at the probe input in MachPro.interface.

Procedure

1. De-energize the cabinet.

2. RouteSelect an unused M31 input for the TP400 probe cable(example: separately from motor and VFD (variable frequency drive) output cables.1DI.01.xx).

Connect probeTP400 power:power and select output type:

A. Set TP400 as NO (Normally Open)

• • • Connect Green to 0 VDC.
    • Connect Red to +24 VDC.

B. Set TP400 as NC (Normally Closed)

• • • Connect Green to +24 VDC.
    • Connect Red to 0 VDC.

1. Connect TP400 +24probe Vstatus DCoutput to the M31 PNP input:

   • Connect Black to +24 VVDC DC(same field24 supply.VDC supply used for M31 inputs).

   • Connect TP400 0 V DCBlue to the 0 V DC field supply (the same 0 V DC reference used by theselected M31 inputs)DI terminal (1DI.01.xx).

Result:

• In NO mode, the signal goes to +24 VDC only when the probe triggers.

• In NC mode, the signal is +24 VDC at rest and goes OFF when the probe triggers.

Connect the TP400cable probeshield output to an M31 input:(recommended):

• Connect the TP400 trigger output wireshield/drain to the selected M31 input terminal.

• Make sure the input is configured in MachPro as the probe input.

Connect 0 V DC correctly (recommended cabinet practice):

1. Tie all 0 V DC terminals (power supply 0 V, drive I/O 0 V, M31 I/O 0 V) to a single 0 V / ground bar.

2. Bond the 0 V / ground bar toenclosure PE at one place only.

Connect the probe cable shield (updated):

1. Connect the probe cable shield to the enclosure ground lug (PE/chassis ground) at the cabinet entry point.

2. Do not connect the cable shield to an M31 0 V terminal.end.

3. Do not connect the shield atto the probeM31 end0 unlessVDC you have a defined EMC (electromagnetic compatibility) plan and equipotential bonding.

4. Use a 360° shield clamp or gland if available. Keep any pigtail as short as possible.

Reference

TP400 electrical notes

• The TP400 uses shielded cable.

• Input power is 24 V DC (±10%).

• The TP400 output load current limit is 50 mA (maximum).terminal.

Shield termination rules of thumb (for this application)

• Terminate the shield at one end only (cabinet end) to reduce ground-loop risk.

• Prefer a low-impedance, 36 “pigtails”). lug is better than an M31 0 V terminal
  A cable shield workending the noise to ground through a low-impedance path. A shield that is not grounded, or is grounded through a high-impedance path, is less effective.

If you connect the shield to 0 V DC at the controller, shield current can flow in the same conductors used as the signal reference for inputs. This can shift the input reference and cause false input transitions.

Connecting the shield to chassis ground (PE) keeps shield current out of the 0 V DC signal reference. Rockwell’s wiring guidance shows this approach: ground the shield at one end and connect it to a chassis mounting bolt.

About pigtails vs 360° clamps

Single-point terminations that use a drain wire or pigtail can reduce shielding effectiveness because the exposed length adds impedance and can radiate or receive noise. 360° terminations perform better across a wide frequency range.

Troubleshooting

• Symptom: Probe trips randomly when the spindle starts or during rapid moves.

  • Verify the shield is connected to PE at the cabinet entry and not to M31 0 V.

  • Verify operation:

    • In MachPro, monitor the chosen input state while you trigger the probe by hand.

    • If the probe is wired as NC, set the input as Active Low so the control treats the triggered state as “ON”.

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  Reference

  Why NO/NC changes when you swap Red and Green

  The TP400 documentation states that reversing the power polarity at the probe interface reverses the logic state of the output signal.

  M31 input type

  The M31 inputs are PNP sourcing, 16–24 VDC, and isolated.

  Cabinet 0 VVDC /bonding (MachMotion recommendation)

  Tie all 0 VDC terminals to a single 0 VDC/ground bar isand bondedbond that bar to PE at one point

  only.

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  Explanation

  Shield to 0 VDC vs shield to enclosure PE

  • Shield to 0 VDC can inject noise into the input reference. This can cause unwanted probe triggers.

  • Re-routeShield to enclosure PE sends noise current to the probechassis cableinstead awayof fromthe motor/VFDinput outputreference. cables.This usually improves noise immunity.

  Which mode to use

  • Use NC when you want easier detection of a broken wire or loss of power (the input changes state when the circuit is not healthy).

  • Use NO when you want the input OFF at rest and ON only during probe trigger.

  
  

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