ISE 370: Industrial Automation
Fall 2014
Allen Bradley Micrologix 1000 Programmable Logic Controller
Equipment (P27 Lab)
A-B Micrologix Programmable Controller
Computer with Rockwell Software – RS Logix
Training box with switches and lights
Reading
Allen-Bradley User Manual for the fundamentals of programming the MicroLogix 1000
Safety Precautions
Do not open training boxes to remove wires on the PLC.
The Allen Bradley PLC consists of a built-in power supply, central processing unit, inputs (switch
device), and outputs wired to colored signal lights.
The processor provides control through the use of a processor file. The processor file contains other
files that break-up the program into more manageable parts. The processor file contains controller
information, the main ladder program; interrupt subroutines and any subroutine programs.
The basic instructions used in the ladder programs represent hardwired logic circuits used for the
control of a machine or equipment. The basic instructions are separated into three groups: bit, timer, and
counter. The bit instructions operate on a single bit of data. During operation, the controller may set or reset
the bit, based on the logical continuity of the ladder rungs. The timer and counter instructions consist of
accumulator and preset values. Once the accumulator value is equal to the preset value, the rung changes
from false to true.
Sensing devices located on a machine detect changes in the machine’s condition. For example, a part
arriving at a workstation contacts and closes a limit switch, the sensing device. As a result, a signal goes to
the control panel. At the control panel, the signal enters a bank of relays or other devices such as the solid-1-
ISE 370: Industrial Automation
Fall 2014
state modules. Circuits within the control panel open or close causing additional signals to go to output
devices at the machine. A relay may energize a clamp, which secures the part at the workstation.
Systems run by programmable controllers operate in much the same way. Input sensing devices
report machine conditions; output devices respond to the commands. Wiring between the machine and the
controller provide electrical paths from the sensing devices to the controller and from the controller to the
output devices.
The hardware must be properly addressed so that is relates to the ladder diagram program. In the
ladder diagram program, the input to the output instruction address is associated with a particular I/O
terminal and is identified by the 5-digit address.
Input and output devices are connected to the processor’s input and output module terminals. Each
terminal corresponds to a memory bit that reflects the state of that device. If the device goes on, then we say
the corresponding bit in the data table is set to 1. If the device goes off, we say the corresponding bit in the
data table is reset to 0.
Output instructions are programmed at the end of the ladder-diagram rungs. Only one output
instruction can be programmed on each rung and it is executed only if the instructions preceding it are true.
The Bit controlling instructions are used to set memory bits on or off in any area of the data table, excluding
the processor work areas.
Timer and Counter instructions are output instructions within the processor. They provide many of
the capabilities available with timing relays and solid-state timing and counting device. Usually conditioned
by examine instructions, timers and counters keep track of timed intervals or counted events according to the
logic continuity of the rung. Each timer or counter instruction has two 3-digit values. Each value requires one
word of data-table memory.
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ISE 370: Industrial Automation
Fall 2014
PLC Assignment:
Design and demonstrate ladder logic programs that will carry out the following tasks:
1) Turn each signal light (3) on/off by opening and closing a separate switch for each light.
2) A motor (green light) is switched on by pressing a start switch and the motor remains on until another
stop switch is pressed.
3) Either of two normally open switches has to be closed for a coil (red light) to be energized and operate
an actuator.
4) A heating element (yellow light) is turned on for 7 seconds. The heating element is turned on 5 seconds
after receiving a signal (switch #3) that a part has arrived.
5) Simulate the following operation of an index machine.
> Start an index machine in motion when a start button is pressed (switch #1).
> The index machine takes exactly 3 seconds to change position. (green light).
(The green light must stay on for exactly 3 seconds to simulate the indexing motion).
> A signal is sent to lower & turn on a vertical drill press (red light), which takes exactly 10 seconds
to complete. This also includes the time to raise the drill press back to its original position.
(The red light must stay on for 10 seconds to simulate the drill press operation).
> A signal is also sent to an automated parts feeder (yellow light) that takes exactly 4 seconds to load.
(The yellow light must stay on for 4 seconds to simulate the loading of a part).
> A safety switch (switch #2) will stop the index machine if needed.
> Make sure to keep a count of parts processed through your system in your program for review.
6) A motor speed control (green light) is incremented in speed for each input from a sensor (momentary
switch # 3 actuation) continued with incremental decrease in speed for each input from a sensor
(momentary switch #4 actuation). (Hint: Use up/down counter to track signals. Why doesn’t the green
light go when signal is sent?)
7) An output is switched on by giving a proper input & that output remains on even if the input condition is
changed. (Hint: latching instruction) (model Safety Switch)
Add documentation to your application to describe the configuration and operation of your system.
This documentation can be used to help install, debug, startup, and modify your program.
8) A motor (green light) needs maintenance after 20 seconds of running time. The motor is switched on &
off by pressing a start switch and the motor remains on until switched off. Track the running time only of
the motor and turn on a red pilot light when the motor needs maintenance service. Remember to design
your program for continuous use. After the required maintenance is completed the system must be reset
for the next cycle of use.
9) A sensor counts the arrival of (4) cars before turning a (green light) ON & the (red light) that was ON
goes OFF. After 5 seconds, the green light will go OFF & the red light goes ON. The process must be able to
be repeated.
10). A sensor counts 6 bottles packaged to each case. When the count reaches 6, a counter which counts the
number of cases is incremented by one.
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