Pathway DMX Pathfinder CR Manual - Manual (Page 37)

DMX Distribution System Page 37
DMXPathfinder - Hardware
the exception of "RUN" are controlled by the microprocessor. The RUN LED
is driven from the watchdog timer.
Crosspoint Matrix Section (Sheet 2) -- Two 16 x 4 crosspoint matrix
devices are provided. U14 is the matrix device for data moving in the
transmit direction through the system, and U11 handles data in the return
direction. U11's four channels of input data are derived from the card's data
I/O section. U14's 16 channels of input data come directly off the system
send data bus at J1 via buffers U15 and U16. U11's 16 channels of output
data go directly to the system return bus at J1 via gated buffers U17 thru
U20, which in turn are controlled by demultiplexers U12 and U13. Gating is
required to prevent more than one Output Module from trying to place data
on the frame bus at the same time. Multiplexer U8 is used to monitor activity
on the 4 send and 4 return channels for the purpose of front panel LED
indication.
Data I/O Section (Sheet 3) -- Four identical data I/O subsections are
provided on the module. The second subsection will be described (top left of
sheet). An RS485 transceiver U29 and optocouplers U28/U30 handle data
flow in both directions. Three DPDT impulse-latching isolation relays K4-K6
operate in parallel to selectively connect or disconnect the two data pairs and
common to the external wiring network. 250mA data link Pico fuses are
provided for every connection. Relay status is returned to the
microprocessor by an extra pole of K6. The external field wiring network is
accessed via backplane connector J2, and front panel auxiliary connector J5
allows temporary connection to output signals or monitoring with a DMX
analyzer. L5-L8 are ferrite beads to suppress RFI/EMI emissions from cables
plugged into the auxiliary connector. Note that the four data I/O subsections
operate on supply voltages which are isolated from each other.
Power Supply Section (Sheet 4) -- AC power at 120 volts 60 Hz is brought
to each module by backplane connector J3. A polyswitch (self-resetting)
fuse protects on-board components. JP6 is a power input selection jumper
(E1-E2 and E3-E4 are jumpered for 120 volt operation, E2-E3 are jumpered
for 240 volts). Three transformers T1-T3 are provided, each with two 8 volt
secondary windings. T1's secondaries are paralleled for higher current rating,
then rectified by BR1, filtered by C1 and regulated at 5 volts by VR1. The
resulting VCC supply is used by the processor, matrix and display sections,
as well as for the relay coil supply. T2 and T3 together generate four
separate DC power supplies via full-wave bridge rectifiers BR2-BR5 and 5
volt regulators VR2-VR5. These supplies are specifically for each of the