Exercises For Training with the SimuPLC
1. Program a PLC to control four flames and the oven of a stove, functionning by following way:
ii) When the user presses the "Turn On" button, connected to the first bit input, the output connected to the gas valve of the respective flame is turned on and, after 0.5 seconds, the second output, connected to the device for lighting flame is operated, during 1 second, for lighting of the respective fire. The valve will be turned off only when the "Turn Off" button, connected to the second bit input, is operated; or if there is any problem with the flame, according to item v).
iii) When the user presses the "Temporized Turn On" button, connected to the third bit input, the respective flame, controlled by internal timer inside PLC, stays turned on during the time, in minutes, entered, by way potentiometer, at the first analogical input.
iv) When the user presses the "Turn On Heating" button, connected to the fourth bit input, the respective flame stays turned on until that the temperature, in celsius degrees, from a thermometer electronic, that measures the heating of the substances or alimony inside of the cans, connected to the second analogical input, reach or overtake the value placed, by way of potentiometer, in the third analogical input.
v) The greatest hazard associated to the operation of a stove is the opening of the gas valve without the immediate combustion of the flame, or its extinguishing before of the closing of the valve, what can imply accumulation and explosion of the scooping gas. Then, in the fifth input a sensor of flame signals that the it one at that fire was, and continues, indeed alight since the command for lighting it. If, by whichever motive, the valve is open and there isn't flame after the ending of the operating of the device for lighting flame, the program turns off immediately the command (which will close the gas valve) and turns on a signal of alarm at that flame, that will be turned off only by the operating of the "Reset" button, connected to the sixth bit input.
vi) Note that the operating of the "Turn off" button or problems with the flame turn off the valve at any of the operation modes, till the temporized or the heating.
vii) Finally, a general switch musts be turned on for the system works. And if it is turned off during the operation of the system, all flames are immediately turned off, by the closing of all gas valves - observe that here these valves stay naturally closed, remaining open only while the respective bit outputs are turned on.
Obs.: the intensity of the flames is controled by manuals valves similars to the used on the conventionals stoves.
2. Write a PLC program that controls automatically the filling parking lot up by following way: there are 255 vacancies for cars and 255 for motorcycles.
There are three photocell at the entrance and at the exit of the parking lot which identify the vehicle entering or exiting by its size, because the first is to, let's say, one meter from second and to two meters from third (adjust such measured to the intended dimensions) – a motorcycle operates the 1st and the 2nd and, after, the 2nd and the 3rd at the same time, but only a car operates the three at the same time; such information will be used by the program to count how many cars and motorcycles are parked, signaling the number of existent vacancies for cars and motorcycles by way of the variables QB0 and QB1, respectively.
To start the system, there is an button that, when be actioned, records the values provided into IB0 and IB1 as the quantities of cars and motorcycles, respectively, that are parked at the moment of the start.
3. We have two panels with twelve little buttons NO, ten numbered from 0 to 9 and two special * and #. One of the panels was installed of the side of out of the gate of a house and the other stays barred inside of a compartment into of the house.
How to do that a PLC, after of the pressing of the button # at the panel of inside, store the four buttons pressed following as the password that will must be typewritten on the panel of out to open the gate by functioning of a motor, get it 10 seconds open and after close it automatically, unless that the absence of beam light on photocell placed adequately signals which the car still is passing by the gate, when then the PLC will wait that the beam light back to reach the photocell to proceed the closing?
In addition of the panel, inside of house there is too a button that, independent of password, opens the gate, whose closing, in this case, likewise is by same way explained in the anterior paragraph.
Obs.: there is a external circuit attached to the control of the motor, it being sufficing that the PLC enact on the two points of the circuit "Opening the Gate" and "Closing the Gate" through by two outputs bit.
How to improve the program to it accept too a security password, entered like the former, but after pressing of the button *, that as well will allow opening of the gate, but, at the same time, will action a alarm signal (what can turn on signaling inside of the house, action a help request to firm of security and/or to near policial bureau, make a telephone calls, etc.).
Obs.: this security password can unveil extreme worth in the case the resident be dominated by invaders at the moment he/she is coming in house.
Copyright © 2002
André Luiz Barbosa
All rights reserved.