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Mounting
Using the PCB support hardware in hardware pack H118-F,
or equivalent, mount the Multi-SD on a flat surface using
all four mounting holes for maximum support. To
minimize EMI, securely mount the unit on a grounded
surface using a metal spacer and hardware at the mounting
hole that is surrounded by a conductive pad.
CONNECTIONS
Connector Pin Assignments:
A description of the function of each connector pin and
location is listed in Table 1. Depending on the model
number and configuration of the Multi-SD, some headers
may not need to be connected.
Suggested Connecting Hardware
Use CRI Hardware Pack H118-F containing the following
components shown in Table 2.
Input Power Connection to header J1
Refer to Figure 1 for input power wiring. One or two
power supplies in the range of 30 to 75 VDC should be
connected at header J1. If two power supplies are used,
they are logically OR’d on the Multi-SD so that the
operating voltage is equal to the higher of the two supplies.
An OR’ing diode is located in the A & B power supply
reference legs. The Multi-SD can supply up to 4.0 Amps
(still air) and 5.0 Amps (200 LFPM air stream) at 12, 24
VDC or 48 VDC to the fan load.
–48 VDC Telecomm Power System Note: When a –48
VDC power system is used to supply power to the Multi-
SD, connect –48 VDC Power Return to J1:+ and –48 VDC
Power to J1:A or J1:B.
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Fan Connection to header J2
Fans are connected to header J2. Refer to Figure 1 for
details of fan power wiring. More than one fan can be
connected in parallel to header J2 as long as the total
current draw of the fan load does not exceed the rating of
the Multi-SD.
Connection of Remote Thermistor(s) to header J8
One to three thermistor sensors can be connected to the
Multi SD to provide temperature based fan speed control
and alarming. Referring to Figure 1, connect the
thermistor(s) to header J8. There is no polarity
consideration when connecting the sensor(s). The
thermistor reading the highest temperature is used for
speed control and alarming. If no sensors are connected to
header J8, fans continually operate at full voltage and the
temperature alarm output at header J4 is open.
Connection of PWM Control Signal to header J8:T3
The Multi SD can control fan speed based on an isolated
PWM control signal. Referring to Figure 2, connect the
voltage signal to header J8:T3. Header J8:T3 is internally
pulled up to 4 VDC with a 10.0k Ohm resistor. Isolation
of PWM signal is required because the circuitry at J8:T3 is
referenced to a floating voltage on the Multi-SD. When a
PWM signal is applied to J8:T3, no connections should be
made to T1 or T2.
Connection of an alarm circuit to header J4
An optically isolated open collector circuit output is
connected to header J4 to provide remote indication of a
high temperature condition. Referring to Figure 1, connect
logic circuitry to header J4. The alarm outputs must be
current limited as shown in Figure 1.
Multi-SDs featuring the MOS relay alarm output should be
connected as indicated in Figure 1 except that the current
limiting resistor value is calculated using R1 = V1/100mA
(Ohms), where V1 can be up to 230 VAC.
Connection of a fan speed up input signal to header J5
A non-isolated input is located at J5 that allows the user to
command the fans to full speed when a short circuit is
placed across the two header pins. Refer to Figure 1 for
wiring details.
Speed Up Command from a Tachscan-3: An example of
how this input can be interfaced with the Tachscan-3 is
shown in Figure 3. In this case, the normally open isolated
alarm output (J8:2A, 2B) from the Tachscan-3 is
connected to header J5 on the Multi-SD. When the
Tachscan-3 senses that the speed of one or more fans drops
below the trigger speed, the output closes and the Multi-
SD increases the speed of the fans to full. See the
Tachscan-3 product pages for additional details. Similar
configurations can be used with the Tachscan-9.
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