Application Notes

Basic I/O operation

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This tutorial covers the basics of connecting and using the I/O points on your IMS motion control products.

This basic tutorial covers the following concepts as they apply to the Liberty* MDrive and MDrive/MForce.

  1. Sinking I/O
  2. Sourcing I/O
  3. I/O cabling best practices

Though the design of the I/O points differ between Liberty* MDrive and MDrive MForce products, these basic concepts are relevant to both product families.


  • Liberty* MDrive
  • MDrive Linear Actuator
  • MDrive Plus
  • MForce
  • Motion, Drives & Controllers



Design variations between products

Liberty* MDrive inputs:

  • +5 to+24 VDC
  • Isolated (optical)
  • Fixed as inputs

Liberty* MDrive outputs:

  • +5 to+24 VDC
  • Isolated (optical)
  • Fixed as outputs
  • Dry-contact type

MDrive/MForce I/O

  • +5 to +24 VDC
  • Programmable as input or output
  • No isolation

Sinking I/O

Sinking: A sinking device provides a path for the current to ground. Terms used to describe sinking devices include NPN, Open Collector, Normally High, and IEC Negative Logic.

Sinking input

Sinking input
Figure 1: Sinking input

Sinking output

Sinking output
Figure 2: Sinking output

Sourcing I/O

Sourcing :A sourcing device provides the power or a positive potential to an I/O point. Sourcing devices ‘push’ the current through the load. Other terms used to describe sourcing devices include PNP, Open Emitter, Normally Low, and IEC Positive Logic.

Sourcing input

Sourcing input
Figure 1: Sourcing input

Sourcing output

Sourcing output
Figure 2: Sourcing output


The impact of electrical noise in a system is greatly reduced by following a few basic practices: Signal cabling should be 22 AWG, shielded twisted pairs.

  1. Provide adequate strain relief for all cables.
  2. Minimum cable bend radius = 4 x cable diameter.
  3. Cut the shield at the I/O device end, leave floating.
  4. Connect the shield at the Motion Control Device end earth.
  5. Ensure that all earth connections to the control cabinet are free of paint.
  6. Do not run power cabling alongside signal cabling.
  7. Keep grounds as short as possible.
  8. If a secondary shield is used over the primary, tie both ends of the secondary shield to earth.

Cabling best practices

Cabling best practices
Cabling best practices

*Previously Lexium

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