Equipments (Devices) > PLC200 > Program > Hardware > P

Block that generates a PWM signal with a certain number of pulses at the selected digital output, following an up and down ramp at the frequency.

Ladder Representation

P_RAMP_V2_G0_dev

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN	BOOL	Block enabling
	Pulses	DWORD UDINT	Total number of pulses of the block execution
	Frequency	DWORD UDINT	Maximum frequency to be reached
	RampTime	DWORD UDINT	Ramp time [ms]
	Steps	BYTE USINT	Steps to increase frequency
	OutputNumber	CONST BYTE	Output for the signal to be generated
VAR_OUTPUT	DONE	BOOL	Output enabling
VAR	P_RAMP_INST_0	P_RAMP	Instance of access to block structure

Operation

When the EN input is TRUE, the block generates a PWM signal at the selected output. Initially, it generates an up ramp, starting from zero frequency to the Frequency value (between 0 and 200 KHz), based on the Time and Steps settings. At the appropriate moment, the block generates a down ramp, with the same profile as the up ramp, until the frequency is zero and the Pulses value is reached.

When the Pulses value is reached, the DONE output goes to TRUE.

P_RAMP_graph1

If the EN input goes to FALSE before reaching the number of Pulses, the PWM generation stops immediately.

P_RAMP_graph2

The duty cycle of the signal remains constant at 0.5 throughout the execution of the block.

For the frequency ramp to be generated, each Step must have at least 2 pulses.

If this limitation is not observed, the frequency ramp is not generated, that is, when the block is enabled, the PWM signal starts directly at the Frequency value.

The minimum number of pulses that can be generated is two. However, if the number of pulses to be generated is zero, the block will return success.

NOTE!

If other PWM blocks are running, whichever is called first will have priority.

NOTE!

This block has priority over any coil that is writing data to the selected output.

Example in Ladder

P_RAMP_V2_example01

The above example enables a PWM signal in the DO1 output with initial frequency 0 Hz and duty cycle of 50%. The rise time of the ramp frequency is 500 ms, and the ramp has five frequency steps (0, 50, 100, 150 and 200 Hz). In total executing the block, 1000 pulses will be sent to the output. If the block is successfully completed, the DONE output is activated.

P_RAMP_example02

Example in ST

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

VAR

pulses : DWORD := 1000;

freq : DWORD := 200;

rampTime : DWORD := 500;

steps : BYTE := 5;

start : BOOL := 0 ;

coil : BOOL;

P_RAMP_INST_0 : FB_P_RAMP;

END_VAR

P_RAMP_INST_0.EN := start;

P_RAMP_INST_0(

OutputNumber:=1,

Pulses:=pulses,

Frequency:= freq,

RampTime:=rampTime,

Steps:=steps);

coil := P_RAMP_INST_0.DONE;