Programming instructions

12
The input trigger levels vary, depending on the module type. Generally, the input
becomes active at the 2/3 level, then the input becomes inactive at the 1/3 level.
For example, a +24VDC input will become active when the input voltage reaches
16VDC, and the input turns off when the voltage reaches 8VDC.
The standard input point has a 10 millisecond input filter. This is done
deliberately for switch de-bounce. As a limit switch contacts close, the
mechanical contacts actually bounce a little bit, causing the input to turn on and
off rapidly for a short period of time. This 10msec delay allows the switch
contacts time to stop bouncing.
It is possible to adjust the input filter constant for the first 8 inputs. This is
explained in Lesson 14.
Typically if you need to see more than 20 pulses per second, a high speed
counter module or the built-in high speed inputs should be used.
Your base PLC choice will consist of 8, 16, 24, 32, 40, or 64 input points.
Extension units offer either 16 or 24 inputs. Extension blocks offer 8 or 16 points.
All modules are available in sink or source logic.
2.5 Outputs
The output device allows the PLC to control a machine. Integrated outputs are
available on the base unit. If more outputs are required, extension blocks and
units can extend the number of I/O.
0V
24V
ON
OFF
16V
8V
10mSec 10mSec
DIGITAL INPUT is ON
VOLTAGE LEVEL