Remote Processing RPC-30 - Manual (Page 24)

DIGITAL AND OPTO PORTS CHAPTER 6
Page 22 RPC-30
Figure 6-2 Inductive load protection
High current output
Eight lines at J3 can be used as high cur rent driver s.
These outputs will switch loads to ground. Outputs are
controlled by Port B on the 82C55. Its address is 1.
Logic outputs are inverted. That is, when a 1 is written
to the high current port, the output is switched on and
goes low.
The output driver chip, U 1, can be replaced w ith a DIP
shunt jumper so it is like the other lines at J3.
NOTE: Outputs at the high current lines are not
compa tible with TT L logic leve ls and should
not be used to drive other logic devices.
Each of the high current outputs can sink 100 ma at 50V.
WARNING:
External supplies using the high cu rrent outputs m ust
be tied to J3, pin 26 and NOT the power connector.
Failure to do so can produce a ground loop and
cause erratic operation.
The ther mal time constant of the p ackage is ve ry shor t,
s o th e nu m b er o f o u tp u ts th a t a r e on a t a n y o n e t im e
should include those that overlap even for a few
milliseconds.
Incandesc ent lamps h ave a " cold" c urre nt of 11 times its
o p er a ti ng c ur r e nt . L a m ps r eq u ir i ng m o re th a n 5 0 m a
should not be used.
Protection diodes m ust be used with inductive loads.
Refer to figure 6-2
Do not pa rallel outputs f or higher drive. This could
result in damage since outputs will not share current
equally.
Interfacing to an opto-module rack
I/O lines can be interfaced to an MPS-8, 16, or 24
position opto m odule rac k. L ines not going to an opto
module connect to a screw terminal on the MPS-XX
series boards. This feature allows you to connect
s w it ch e s o r ot he r T T L t yp e de v ic e s t o t he d ig it al I/ O
lines. The MPS-XX series boards accept G4 and G5
series modules.
Use the O PTO comm and to acces s and contr ol G4 opto
modules. The LIN E comm and is used to access
i nd iv id u al li ne s on th e ST B -2 6 . A dd 1 00 to a ny L IN E
command to access pins on the STB-26. For example,
LINE(103) r eads pin 3 at J3.
A CMA-26 connects J3 on the RPC-30 to the MPS-XX
board. Cable length should be less than 2 feet for the 8
position rack and 18 inches for the 16 and 24 positions.
Excessive cable lengths will cause a high voltage drop
and consequently unreliable operation. Make sure you
connect ground a nd + 5V to the opto racks.
Use the following table to determine the corresponding
opto channe l for a par ticular 82C 55 port:
Opto 82C55 J3
channels port Address
0-3 Lower C 2
4-7 Upper C 2
8-15 A 0
16-23 B 1
To turn on an opto module, a line must be low. A
module is turned off by writing a ' 1' to a channel. The
logic at por t B, w ith the high cur rent outpu ts installed is
just the reve rse. A ' 1' at a line causes the module to
t ur n O N .
High cur rent outpu ts at port B ar e optionally
configurable as TTL I/ O by replacing U1 with a DIP
shunt jump er. This will kee p the logic com patible with
ports A and C. If opto channels 16-23 are used as
inputs, then U1 must be replaced by a DIP shunt jumper.