PWM Variable Speed Control
© 2019 EMP, Inc.
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will turn off at 8% duty cycle. Because of tolerance stackups, component variation over temperature and
inconsistencies in the incoming PWM signal, it is recommended that some margin is given for the minimum and
maximum speed set-points. For example, using 12% duty cycle as the minimum speed in lieu of 10% will allow
for some margin to compensate for the above mentioned factors.
NOTE:
Fans allow a reverse command. Pumps do not allow a reverse command.
0% to 2%
3% to 9%
10% to 90%
91% to 92%
93% to 98%
99% to 100%
Invalid PWM
command,
motor goes to
default speed
Zero rpm
command
Min to Max speed
(linear ramp), once
running motor will
shut off below 8%
Max rpm
command
Max rpm, normally
reserved for reverse
commands
Invalid PWM
command, motor
goes to default
speed
0% to 2%
3% to 9%
10% to 90%
91% to 92% 93% to 98%
99% to 100%
Invalid PWM
command, motor
goes to default
speed
Zero rpm
command
Min to Max speed
(linear ramp), once
running motor will
shut off below 8%
Max rpm
command
Reverse
command
Invalid PWM
command,
motor goes to
default speed
NOTE:
When controlling fan speed using PWM, the component will automatically skip over the speed range
of 2900 rpm to 3300 rpm for pullers and 2850 rpm to 3250 rpm for pushers to avoid a resonance.
