1 3 and 9 28 Manufacturing Engineering Technology 7th Editi

1- 3 and 9- 28 Manufacturing Engineering & Technology 7th Edition

Review Questions L Describe the timer base value of a timer instruction I 2 Describe the retentive and the non-retentive timer instructions. \' Describe the functions of ON-delay and OFF-delay timers. 4 In the Allen-Bradley SLC 500 series PLC, how are the preset and the accumulated timer registers addressed? 5 How is a retentive timer in an Allen-Bradley SLC 500 series PLC reset?

Solution

1.

A time base is a special type of function generator, an electronic circuit that generates a varying voltage to produce a particular waveform. Timers are typically programmed with several different time bases. Suppose time base is set to 0.1 and delay increments is set to 50, then the timer has 5 seconds delay that is, (0.1 x 50).

2.

Timers that do not lose their accumulated time whe the enable input line transitions to low again are known as retentive timers. They continue to maintain accumulated time and increment the time when the input line goes to high again whereas non-retentive timers lose the accumulated time whenever input transitons is enabled to low. The accumulated time resets to zero.

3.

Timer ON-delay turns an output on after a timer has been on for a preset time interval. It starts accumulating time when rung becomes true and continues to do so until either accumulated value equals preset value or the rung conditions becomes false.

Timer OFF-delay is used to turn an output ON or OFF after rung has been off for a desired time. It starts accumulating time when rung becomes false and continues to do so until the accumulated value equlas the preset value or the rung becomes true.