164
ifm
System Manual
ecomat
mobile
SmartController (CR2500) V05
PWM in the ecomatmobile controller
PWM signal processing
Example:
The PWM frequency shall be 200 Hz.
2.5 MHz
_________ = 12 500
10
= 30D4
16
200 Hz
RELOAD value = 10 000
16
– 30D4
16
= CF2C
16
Thus the permissible range of the PWM value is the range from CF2C
16
to FFFF
16
The comparison value at which the output switches must then be between CF2C
16
and
FFFF16
.
NOTE
The PWM frequency is the same for all PWM outputs (4...7 or 4...11).
The functions PWM and PWM1000 must not be mixed.
This results in the following mark-to-space ratios:
Mark-to-space ratio
Switch-on time
Value for mark-to-space ratio
Minimum 0
%
FFFF
16
Maximum 100
%
CF2C
16
Between minimum and maximum triggering 12 500 intermediate values (PWM values) are possible.
NOTE
for ClassicController and ExtendedController applies:
If the PWM outputs 4... 7 are used (regardless of whether current-controlled or via one of the PWM
functions) the same frequency and the corresponding reload value have to be set for the outputs 8...11.
This means that the same functions have to be used for these outputs.
PWM dither
For certain hydraulic valve types a so-called dither frequency must additionally be superimposed on
the PWM frequency. If valves were triggered over a longer period by a constant PWM value, they
could block due to the high system temperatures.
To prevent this, the PWM value is increased or reduced on the basis of the dither frequency by a
defined value (DITHER_VALUE). As a consequence a vibration with the dither frequency and the
amplitude DITHER_VALUE is superimposed on the constant PWM value. The dither frequency is
indicated as the ratio (divider, DITHER_DIVIDER * 2) of the PWM frequency.
