Unit installation

12-1
RLC-3 V1.80 Copyright © 1998 Link Communications Inc. 9/17/98
Chapter 12: I/O Board
About the I/O Board:
The RLC-3 will support up to two I/O boards. Each I/O board provides eight logical inputs, eight
logical outputs and eight analog input lines. They are all handled totally separately in software;
each command applies to only one of the three types of lines. Each type will be described below.
Please note that you can control how often the RLC-3 checks the input line and analog alarms by
using Command 020 to change the reset value of timer 034. The default is to check the alarms
once per second.
Logical Input Lines:
The logical input lines are used to detect whether a line is "high" or "low". High means that the
voltage read by that line is above approximately 2.5 volts. Low means that the voltage is below
about 1 volt. The range between 1 volt and 2.5 volts is indeterminate. If the line is not connected,
a 47K internal pullup resistor to 5 volts will make the line read high. This pullup allows you to
easily read whether a switch is open or closed. Simply connect the switch between the input line
and ground. If the switch is closed, the input will read low. If the switch is open, the pullup
resistor will make the input line read high. The input line can handle voltages up to +40 volts. Do
not apply negative voltage to an input line.
Input lines can be used in three ways.
• Command 090 can read an input line and tell you whether it is high or low.
• There is also a way to assign a custom voice message to each state of an input line, such as "door
open" and "door shut" (instead if high and low). To do this, program the voice messages you want
to be spoken for the high and low states into the input line macros (see automatic macros starting
with number 324 in Chapter 8). You can then cause the appropriate message to be spoken by
executing Command 091.
• If you want a message to be spoken whenever an input line changes from high to low or low to
high, you can cause the macros you programmed in the step above to automatically be executed at
those times by enabling an "input line alarm" with Command 092. You could use this feature along
with a door switch to tell you when someone opens or closes a door.
Logical Output Lines:
The logical outputs are "open collector" outputs. That means that they can connect the output line
to ground (turn it on) or disconnect it (turn it off). The output lines never output any voltage. The
way they are commonly used is to connect one lead of the coil of a relay (or whatever else you
want to control) to 12 volts and the other lead to an output line. When the output is turned on and
applies a ground, the coil of the relay will be energized and will turn the relay on. The output line
can "sink" (apply a ground of) about 150 milliamps. Connecting an output line directly to a power
supply and turning it on will destroy the output driver IC. Make sure that whatever you are turning
on and off draws less than 150mA.