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CUSTOMIZING YOUR CONTROL CURVE (figure 7) The off-the-shelf Cirrus is designed to give the user
optimum flexibility in experimenting with control
parameters. Once the desired control parameters are
chosen, the user may order their own customized
version of the Cirrus preprogrammed with the desired
control curve and other custom features avoiding switch
and potentiometer settings. Refer to figure 7 below when
setting switches 5,6 and 7 
Figures 7
Until this point, all settings can be made without power,
control signal or fans connected. From here on, the
Cirrus must be powered, fans connected and an
adjustable control signal (decade box or other resistance
substitute to simulate a thermistor, an adjustable voltage
source for voltage control or adjustable current source
for current control or to simulate a transducer) must be
connected to the board. (see CONNECTIONS section
for details).
For steps A – H, switch 8 will activate and deactivate
POT1 for programming, to avoid accidental
programming errors be sure to deactivate POT1 by
turning switch 8 OFF before changing switches 5,6 or 7.
A) Transducer or Alarm Power When controlling from a remote transducer or powering
an alarm, the Cirrus can be used as a power source up
to 18VDC (see figure 9 below). If not powering a transducer or
alarm, skip this step. To set the supply voltage, set
switches 5-OFF, 6-OFF, 7-OFF (see table 3 below), then set
switch 8 to the ON position. Place a multimeter across
OUT and GND and adjust POT1 until the desired voltage
is set. When finished, set switch 8 to the OFF position.
B) Setting PWM Frequency The standard Cirrus can control PWM controllable fans
between 1000Hz and 10,000Hz. Check your fan for the
specified PWM signal. To program for this signal, set
switches 5-ON, 6-OFF, 7-OFF (see table 3 below), then set
switch 8 to the ON position. Adjust POT1 for the closest
setting to the PWM signal specified for your fan (see
figure 6 below). When finished, set switch 8 to the OFF
position. Note: POT1 settings are not graduated, knob
alignment need not be exact. 
C) Setting Full Speed Duty Cycle (Y2)With the fan or fans powered, adjust POT1 to the full
speed required for your application (see figure 7 above). The
appropriate speed can be determine using a strobe light,
flow meter, sound level meter or measuring temperature
rise, this is purely application specific. Set switches 5-
ON, 6-ON, 7-OFF, then set switch 8 to the ON position.
When finished, set switch 8 to the OFF position. Note:
When determining Y2, make sure the air mover is
loaded to simulate actual operation conditions. An air
mover that is not loaded will provide inaccurate results.
D) Setting Idle Speed (Y1) With the fan or fans powered, adjust POT1 to the idle
speed required for your application (see figure 7 above). The
appropriate speed can be determine using a strobe light,
flow meter, sound level meter or measuring temperature
rise, this is purely application specific. Set switches 5-
OFF, 6-OFF, 7-ON, then set switch 8 to the ON position.
When finished, set switch 8 to the OFF position. Note:
When determining Y1, make sure the air mover is
loaded to simulate actual operating conditions. An air
mover that is not loaded will provide inaccurate results. |
E) Setting Minimum Control Input (X1) With the fan or fans powered, simulate the minimum
control input (see figure 7 above) across J4, GND - IN using a
resistance to simulate a thermistor (refer to table 4),
voltage or current to simulate a transducer. Set switches
5-ON, 6-OFF, 7-ON, then set switch 8 to the ON
position. Set switch 8 back to the OFF position.
H) Setting Tach Alarm Threshold Most PWM controllable fans will indicate fan speed from
a tachometer circuit that senses Pulses Per Revolution
(PPM). The Cirrus can sense these pulses and send an
alarm signal through J4 when a minimum threshold is
reached. If no alarm is to be connected, skip this step.
