Siemens SIMATIC S7-1500 Manual page 17

Product overview
2.2 Functions
Example for energy saving by reducing the holding current
High starting current is required to activate a solenoid valve. When the solenoid valve is
activated, the current requirement is lower; it only has to be held in position. This time-
dependent current requirement can be met well with the PWM function.
The "ValveControl" function block shown below sets the holding current required by a
solenoid valve only after the configured time (HoldTime) has expired. You can generate the
required holding current with a duty factor (PWM duty cycle << 100%). While "HoldTime" is
running, the output is set (duty factor = 100 %) to generate a high starting torque for the
solenoid valve.
FUNCTION_BLOCK "ValveControl"
{ S7_Optimized_Access := 'FALSE' }
VERSION : 0.1
VAR_INPUT
END_VAR
VAR_OUTPUT
END_VAR
VAR
TON;
END_VAR
BEGIN
#Hold_TON(IN:=#OutputTrigger,
IF #OutputTrigger = FALSE THEN
END_IF;
IF #Hold_TON.Q THEN
ELSE
END_IF;
END_FUNCTION_BLOCK
16
OutputTrigger : Bool; // Binary control of the output
HoldTime : Time; // Lenght of time until the PWM output begins
PWM_DutyCycle : Int; // PWM duty cycle after hold time
PWM_Out : Int; // Value for PWM output
Hold_TON {OriginalPartName := 'TON'; LibVersion := '1.0'} :
PT:=#HoldTime);
#PWM_Out := 0;
RETURN;
// Hold time expired => switch to PWM mode
#PWM_Out := #PWM_DutyCycle;
// Control output to 100% during hold time
#PWM_Out := 1000;
DQ 8x24VDC/2A HF Digital Output Module (6ES7522-1BF00-0AB0)
Manual, 06/2018, A5E03485650-AF