====== Pulse width modulation signal ======

{{:en:mervis-ide:35-help:b87.png}}

===== Block name =====

B87_PULSE_WIDTH_MODULATION

===== ST call =====

<code st-iec>
PROGRAM TEST_B87
   VAR
 BOOL1,BOOL2 : BOOL;
 REAL1 :REAL;
    TIME1 : TIME;    
   FB: LIB.CORE.V1_0.B87_PULSE_WIDTH_MODULATION;
   END_VAR
 FB(IN:= REAL1, ENABLED:= BOOL1,T:=T#10S,MIN:=0,MAX:=100,OUT=>BOOL2,TRES=>TIME1);
END_PROGRAM
</code>

===== Library =====

LIB\CORE

===== Version =====

V1.0

===== Description =====

The block generates PWM (pulse width modulation) signal with variable duty time according to the input signal.

===== Inputs =====

|Input |Type|Description                      |Default value|
|IN    |REAL|Input value                      |0            |
|ENABLE|BOOL|Generator enable (true = running)|True         |
|T     |TIME|Signal period                    |15m          |
|MIN   |REAL|Value for duty time = 0 %        |0            |
|MAX   |REAL|Value for duty time = 100 %      |100          |

===== Outputs =====

|Output|Type|Description                            |
|OUT   |BOOL|PWM output                             |
|OUTN  |BOOL|PWM output negated                     |
|TRES  |TIME|Remaining time to the end of the period|

===== Function =====

he block generates PWM (pulse width modulation) signal. The  analogue input //In// is converted to binary pulsing signal with period of //t//. The input signal value is proportionally converted  (for //min// <= //In// <= //max//). If //In// <= //min// then //out// = false, if //In// >= //max// then //out//=true permanently.

The output //outn// is a negated value of //out//. The block also provides remaining time to the end of the current period //tres//.

The input //enable// sets //out//=false and //tres//=0, if set to False.

===== Function in case of wrong setting =====

If //in// is hidden or //min// > //max// or //min// <= 0 then //out//= false.

{{:en:mervis-ide:35-help:b87_1.png}}

===== Application example =====

{{:en:mervis-ide:35-help:b87_example.png}}\\


The block is used as a signal generator for thermic valve actuators or electric heating bodies controlled by solid state relays. It is preferred to use dedicated I/O modules (Domat M312, M313). Do not use mechanical relays to control the power circuits as the number of switching cycles may be too high for mechanical relays.