Encoder loss setup – Delta Tau 5xx-603869-xUxx User Manual

Page 33

Brick Motion Controller Hardware Reference Manual

System Wiring

Encoder Loss Setup

The Brick Motion Controller has encoder-loss detection circuitry for each encoder input. Designed for
use with encoders with differential line-driver outputs, the circuitry monitors each input pair with an
exclusive-or (XOR) gate. If the encoder is working properly and connected to the Brick Motion
Controller, the two inputs of the pair should be in opposite logical states – one high and one low –
yielding a true output from the XOR gate.

Note

A single-ended encoder cannot be used on the channel Encoder-Loss Errors

For the Brick Motion Controller Controller Encoder-loss detection bits come in the locations shown in the
table below.

Channel# Address

Description

Encoder #1

Y:$78807,0,1

Encoder #1 Loss Input Signal

Encoder #2

Y:$78807,1,1

Encoder #2 Loss Input Signal

Encoder #3

Y:$78807,2,1

Encoder #3 Loss Input Signal

Encoder #4

Y:$78807,3,1

Encoder #4 Loss Input Signal

Encoder #5

Y:$78807,4,1

Encoder #5 Loss Input Signal

Encoder #6

Y:$78807,5,1

Encoder #6 Loss Input Signal

Encoder #7

Y:$78807,6,1

Encoder #7 Loss Input Signal

Encoder #8

Y:$78807,7,1

Encoder #8 Loss Input Signal

As of this writing, there is no automatic action taken on detection of encoder loss. Users who want to
take action on detecting encoder loss should write a PLC program to look for a change in the encoder loss
bit and take the appropriate action. Generally, the only appropriate response is to kill (open loop, zero
output, disabled) the motor with lost encoder feedback; other motors may be killed or aborted as well.

This next example program reacts to a detection of encoder loss. This is a more serious condition than a
count error, so a “kill” command is issued when the loss is detected. The example is for a single axis only,
but is easy to duplicate for multiple axes.

; Substitutions and definitions

#define Mtr1OpenLoop

M138 ; Motor status bit

Mtr1OpenLoop->Y:$0000B0,18,1

; Standard definition

#define Enc1LossIn

M180 ; Input loss-detection bit

Enc1LossIn->Y:$078807,0,1

; Brick Motion Controller Ch1 loss bit

#define Mtr1EncLossStatus

P180 ; Internal latched status

#define Lost

; Low-true fault here

#define OK

; High is encoder present

; Program (PLC) to check for and react to encoder loss

OPEN PLC 18 CLEAR

; Logic to disable and set fault status

IF (Mtr1OpenLoop=0 AND Enc1LossIn=Lost)

; Closed loop, no enc

CMD^K

;

Kill

all

motors

Mtr1EncLossStatus=1

; Indicate encoder loss

ENDIF

; Logic to clear fault status

IF (Mtr1OpenLoop=1 AND Enc1LossIn=OK AND Mtr1EncLossStatus=0)

Mtr1EncLossStatus=0

; Indicate valid encoder signal

ENDIF