Equipments (Devices) > PLC200 > Program > Hardware

Block that reads the value of pulses from an encoder according to a chosen type of reading, displaying to the user his current position in revolutions and the speed in RPM.

Ladder Representation

READENC4_block

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN	BOOL	Block enabling
	SOURCE#	BYTE	Counting source
	PPR	WORD	Number of pulses corresponding to a turn
	FILTER	REAL	Time constant of the input filter
VAR_OUTPUT	ENO	BOOL	Output enabling
	SPEED	REAL	Speed in RPM
	POSITION	REAL	Current position of the encoder, in revolutions
VAR	READENC4_INST_0	READENC4	Instance of access to block structure

Operation

When this block has a TRUE value in EN, it gets the number of encoder pulses counted since energization of the PLC300 as selected on SOURCE #, and calculates the number of absolute revolutions through the PPR argument, inserting the result in POSITION. The value of SPEED is calculated by means of an internal time base of the block. Further, the block allows filtering of the signal with an output filter determined by FILTER.

When EN has FALSE value, POSITION and SPEED remain unchanged.

The ENO value forwards to the next Ladder block the EN value after the operation is completed.

Compatibility

Device	Version
PLC300	2.10 or higher

Block Flowchart

READENC4_flowchart

Example in Ladder

READENC4_example01

The example above when identifying a leading edge on DI1, gets the number of pulses of the encoder connected in quadrature conformation in the fast inputs since energization equipment. PULSES_IN_TURN is the value of pulses to complete a turn. TURNS stores the value of the pulses interpreted as revolutions, according PULSES_IN_TURN, and SPEED stores the current speed of the encoder. The block ends with success, ENO output is activated.

Example in ST

The example below displays the instructions for applying the example above in the ST language.

VAR

PULSES_IN_TURN : WORD;

TAU_FILTER : REAL;

SPEED : REAL;

TURNS : REAL;

READENC4_INST_0 : FB_READENC4;

END_VAR

READENC4_INST_0.EN := DI1;

READENC4_INST_0(Source:=1, PPR:=PULSES_IN_TURN, FILTER:=TAU_FILTER);

SPEED := READENC4_INST_0.SPEED;

TURNS := READENC4_INST_0.POSITION;

DO1 := READENC4_INST_0.ENO;