Page 202 - Programmable Logic Controllers, Fifth Edition - Mobile version

The operation of this system can be summarized
as follows: 14. Write a program to operate a light according to the
following sequence:
• The conveyor is started by pressing the start • A momentary pushbutton is pressed to start the
button. sequence.
• As each box passes the photoelectric sensor, a • The light is switched on and remains on for 2 s.
count is registered. • The light is then switched off and remains off
• When the preset value is reached (in this for 2 s.
case 12), the conveyor belt turns off. • A counter is incremented by 1 after this
• The forklift operator removes the loaded pallet. sequence.
• After the empty pallet is in position, the forklift • The sequence then repeats for a total of 4 counts.
operator presses the remote reset button, which • After the fourth count, the sequence will stop and
then starts the whole cycle over again. the counter will be reset to zero.

Programming Counters Chapter 8 183

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