5 Function blocks
5.27 PW, pulse width modulation
Control Relay easy800 11/11 MN04902001Z-EN www.eaton.com 237
5.27 PW, pulse width modulation
This function block is available for easy806-SWD from device version 01 and
for easy800 standard devices from device version 04. EASY802-DC-SWD is
not available as this does not have any local outputs.
The PW.. function block modulates the mark to space ratio of a square wave
signal. It therefore changes the ratio of on and off time and the pulse
duration. The period duration of the signal stays constant.
The function block can be used to convert the manipulated variable of a PID
controller into pulses. The maximum frequency is 200 Hz.
This corresponds
to
a
minimum period duration
of
5ms.
The
maximum
period
duration
is
65.5 s.
Two function blocks are available: PW01 and PW02. Both function blocks are
permanently assigned the device outputs Q01 and Q02: If you use the
PW01, the pulse sequence is output at device output Q01; with the PW02
function block, the device output Q02 is activated. When the outputs Q01
and Q02 are used with the PW function block, they must not be used again
in the circuit diagram. The reason for this is that the PW function blocks
overwrite all other status changes at the device outputs Q01 and Q02.
This can cause unpredictable switching states.
Contacts and Coils
Example
Figure 171:Wiring the enable coil
The enable coil PW..EN is directly assigned to marker M25.
Figure 172:Wiring of the signal contact
The function block contact PW..E1 signals to marker M12.
￫
When using the pulse width modulation function block with a
minimum on time of less than 1 s only use devices with
transistor outputs.
￫
Avoid unforeseeable switch states. Only use each coil of a relay
once in the circuit diagram.
Contacts
Meaning
PW..E1 Error: Time below minimum on or off duration
Coils
Function
PW..EN Selective activation of the function block
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