Delta Tau 5xx-603869-xUxx manual Encoder Loss Setup, Channel# Address Description

Brick Motion Controller Hardware Reference Manual

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		; Motor status bit
#define Mtr1OpenLoop	M138
Mtr1OpenLoop->Y:$0000B0,18,1	M180	; Standard definition
#define Enc1LossIn		; Input loss-detection bit
Enc1LossIn->Y:$078807,0,1	P180	; Brick Motion Controller Ch1 loss bit
#define Mtr1EncLossStatus		; Internal latched status
#define Lost	0	; Low-true fault here
#define OK	1	; 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
CLOSE
System Wiring	25