Adjustable timer application example – Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) User Manual

Page 498

Appendix E
Application Example Programs

E–55

The following application example illustrates the use of timers to adjust the
drill dwell time at the end of the machines downstroke. For a detailed
explanation of:

•

LD, TON, and OSR instructions, see chapter 8.

•

LES and GRT instructions, see chapter 9.

•

ADD and SUB instructions, see chapter 10.

Valid dwell times are 5.0 seconds to 120.0 seconds. Adjustments are made in
2.5 second intervals.

Each time I/8 or I/9 is depressed, the timer preset or delay is adjusted up or
down accordingly. By altering the value of N0 the amount of change can be
increased or decreased. The constants in the LES and GRT instructions, and
in the source and destination of the ADD and SUB instructions, could be
changed easily to integers for even greater flexibility.

Adjustable Timer Ladder Program

Rung 2:0
Adds 2.5 seconds to Timer delay each time the increment push button is
depressed. Do not exceed 120.0 seconds delay. Note that N7:0=250.

| Increment |
| Timer preset |
| I:0 +LES–––––––––––––––+ B3 +ADD–––––––––––––––+ |
|––] [––––––+LESS THAN +––––––[OSR]–––+ADD +––––|
| 8 |Source A T4:0.PRE| 0 |Source A T4:0.PRE| |
| | 500| | 500| |
| |Source B 11750| |Source B N7:0| |
| | | | 0| |
| +––––––––––––––––––+ |Dest T4:0.PRE| |
| | 500| |
| +––––––––––––––––––+ |

Rung 2:1
Subtracts 2.5 seconds from Timer delay each time the decrement push button
is depressed. Do not go below 5.0 seconds delay.

| Decrement |
| Timer preset |
| I:0 +GRT–––––––––––––––+ B3 +SUB–––––––––––––––+ |
|––] [––––––+GREATER THAN +––––––[OSR]–––+SUBTRACT +––––|
| 9 |Source A T4:0.PRE| 1 |Source A T4:0.PRE| |
| | 500| | 500| |
| |Source B 750| |Source B N7:0| |
| | | | 0| |
| +––––––––––––––––––+ |Dest T4:0.PRE| |
| | 500| |
| +––––––––––––––––––+ |

Rung 2:2

Adjustable Timer Application
Example