June 14, 2015
June 14, 2015
June 17, 2015
Energy Conversion and Conservation
26.1597.1 - 26.1597.9
Training Engineers and Technologists via Model TrainsThis paper looks at a novel way to teach Programmable Logic Controls via N-Scale Model trains. Manyelectric machinery courses have a component that covers Programmable Logic Controllers (PLCs), sincethey are widely used in industry to control motors and provide supervisory control for variable speeddrives. A problem with teaching PLCs is that they are used to control large and usually very expensiveequipment. This makes developing a realistic laboratory experience very difficult. Most labs consist oftoggle switches and pushbuttons for inputs and lamps for output. More elaborate process controlsystems are available from several lab equipment manufacturers, but these systems are expensive andthe students sometimes have difficulty understanding the process they are trying to control. Severalyears ago the author began using N-Scale model trains as the system being controlled. This provides asmall and low cost system with the added benefit that the students immediately understand the properoperation. Optical sensors are place around the track for position and speed control. The speed anddirection of the train is set via an analog output from the PLC. Two track switches are also used tochange the train from inner and outer loops. When combined with the existing toggle switches,pushbuttons, and lamps; this makes a realistic system for developing controls. If you add operatorinterface panels, the students can develop full scale systems similar to those found in industry.This paper covers the materials used for the basic N-Scale layout and the additional hardware necessaryto interface with the PLC. The inputs to the PLC are 120 V optical sensors, so no additional interfacing isneeded. The outputs are one analog signal (a variable voltage) and four 120 V digital signals. All ofthese need to be modified. The PLC analog output does not provide enough current to drive the train,so a power op-amp circuit is used. The track switches require 18 V ac, so the 120 V outputs are used tocontrol an 18 V supply via relays.The student response to using this system has been extremely positive. The system has been used byelectrical, industrial, and mechanical engineering students, as well as by electrical and mechanicaltechnology students. As a senior design project, the base system was expanded into an elaboratesystem with four optical sensors, two inductive proximity sensors, and a limit switch that could allowtwo trains to operate simultaneously. The system was also used for special project classes at theundergraduate and graduate level. The student feedback and learning assessments for all these cases isincluded in the paper.
Wrate, G. T. (2015, June), Training Engineers and Technologists via Model Trains Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.24933
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