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User Solutions continued
The PLC is capable of remote access via the internet, but the Park is not currently using
this functionality.
A Need for Speed Control
One of the main control requirements was to limit the speed the cars could travel during the ride. The original ride specifications specified the cars could reach 60 mph. There was concern that the exist-
ing proximity sensors would be able to detect the car traveling at that speed, register it in the PLC and cal- culate train speed—all within a very short window
of time.
The ride is set up in six different zones (stations), and cars are monitored when they enter and exit each zone using proximity sensors. The original prox- imity sensors were very old and failing, so they were replaced. Capacitive sensors were initially specified to detect cars on the track in the new control system, but they didn’t work consistently. New inductive prox- imity sensors were added to the system to monitor the cars movements throughout the ride. The new induc- tive proximity sensors now detect cars reliably.
Figure 3: Status Display
The AutomationDirect Click PLC interfaces to and controls this operator interface panel, providing system status information, along with manual functions based on PLC- monitored sensors and control interlocks.
The original control system sometimes permit- ted cars to collide with one another if the operator was not careful. With the new control system, even if operations are done manually, program interlocks prevent collisions. Operators are warned if they try to push a train into a zone that already has a train (Figure 3).
Control System Details
The design uses two full racks of PLC components. Each rack has a controller and a power supply (Figure 4). The main rack has eight 16-point, 24 VAC/VDC discrete input modules. The second rack has eight 6-point, 5-27 VDC, discrete output mod- ules. AutomationDirect ZIPLink pre-wired connection cables and modules were used to simplify wiring of the many I/O points. The Click PLC was selected
due to the low cost of the controller and related hardware, and for its ability to handle all control functions reliably.
AutomationDirect 24 Vdc power supplies and terminal blocks were also used. A graphics panel was not needed for this project because hardwired pushbuttons and lights were sufficient to provide the required level of operator interface.
Figure 4: CLICK PLC racks
Two racks of AutomationDirect Click PLC hardware are used to monitor safety systems and control train sequencing, brake systems and the air compressor.
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Editor's Note
New Product Focus
- Headless C-more Remote HMI without attached display
- Continuous Flexing Profinet Cable
- ProductivityOpen Arduino-compatible Controller
- Hammond Industrial Enclosures
Tech Thread
Productivity®Open - Maker In, Industrial Out
Business Notes
Cover Story
Does Your PLC Talk JSON?
What's New
User Solutions
Roller Coaster Overhaul
Student Spotlight
Industrial Automation with a Mission
Break Room
Brain Teasers
User Solutions | Issue 43
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