User's Manual

PMAC2A PC104 Hardware Reference Manual

Machine Connections

supply, or the two supplies will fight each other, possibly causing damage. This voltage

could be measured on the TB1 terminal block.

• In a stand-alone configuration, when PMAC is not plugged in a computer bus, it will need an

external ±12V supply only when the digital-to-analog converter (DAC) outputs are used. The

±12V lines from the supply, including the ground reference, can be brought in either from the

TB1 terminal block or from the JMACH1 connector.

Flags Power Supply

Each channel of PMAC has five dedicated digital inputs on the machine connector: PLIMn, MLIMn

(overtravel limits), HOMEn (home flag), FAULTn (amplifier fault), and USERn. A power supply

from 5 to 24V must be used to power the circuits related to these inputs. This power supply can be

the same used to power PMAC and can be connected from the TB1 terminal block or the JMACH1

connector.

Overtravel Limits and Home Switches

When assigned for the dedicated uses, these signals provide important safety and accuracy functions.

PLIMn and MLIMn are direction-sensitive over-travel limits that must conduct current to permit

motion in that direction. If no over-travel switches will be connected to a particular motor, this

feature must be disabled in the software setup through the PMAC Ix25 variable.

Types of Overtravel Limits

PMAC expects a closed-to-ground connection for the limits to not be considered on fault. This

arrangement provides a failsafe condition. Usually, a passive normally close switch is used. If a

proximity switch is needed instead, use a 5 to 24V normally closed to ground NPN sinking type

sensor.

Home Switches

While normally closed-to-ground switches are required for the overtravel limits inputs, the home

switches could be either normally close or normally open types. The polarity is determined by

the home sequence setup, through the I-variables I9n2.

Motor Signals Connections

Incremental Encoder Connection

Each JMACH1 connector provides two +5V outputs and two logic grounds for powering encoders

and other devices. The +5V outputs are on pins 1 and 2; the grounds are on pins 3 and 4. The

encoder signal pins are grouped by number: all those numbered 1 (CHA1+, CHA1-, CHB1+, CHC1+,

etc.) belong to encoder #1. The encoder number does not have to match the motor number, but

usually does. Connect the A and B (quadrature) encoder channels to the appropriate terminal block

pins. For encoder 1, the CHA1+ is pin 5 and CHB1+ is pin 9. If there is a single-ended signal, leave

the complementary signal pins floating – do not ground them. However, if single-ended encoders are

used, check the setting of the resistor packs (see the Hardware Setup section for details). For a

differential encoder, connect the complementary signal lines – CHA1- is pin 7, and CHB1- is pin 11.

The third channel (index pulse) is optional; for encoder 1, CHC1+ is pin 13, and CHC1- is pin 15.