Drum Instruction
Programming
6–2
Drum Instruction Programming
Introduction
The Event Drum (EDRUM) instruction in the DL05 CPU electronically simulates an
electro-mechanical drum sequencer. The instruction offers enhancements to the
basic principle, which we describe first.
Drum instructions are best suited for repetitive processes that consist of a finite
number of steps. They can do the work of many rungs of ladder logic with elegant
simplicity. Therefore, drums can save a lot of programming and debugging time.
We introduce some terminology associated with the drum instruction by describing
the original mechanical drum shown below. The mechanical
drum
generally has
pegs on its curved surface. The pegs are populated in a particular
pattern
,
representing a set of desired actions for machine control. A motor or solenoid rotates
the drum a precise amount at specific times. During rotation, stationary wipers sense
the presence of pegs (present = on, absent = off). This interaction makes or breaks
electrical contact with the wipers, creating electrical
outputs
from the drum. The
outputs are wired to devices on a machine for On/Off control.
Drums usually have a finite number of positions within one rotation, called
steps
.
Each step represents some process step. At powerup, the drum
resets
to a
particular step. The drum rotates from one step to the next based on a
timer
, or on
some external
event
. During special conditions, a machine operator can manually
increment the drum step using a
jog
control on the drum’s drive mechanism. The
contact closure of each wiper generates a unique on/off pattern called a
sequence
,
designed for controlling a specific machine. Because the drum is circular, it
automatically repeats the sequence once per rotation. Applications vary greatly, and
a particular drum may rotate once per second, or as slowly as once per week.
Drum
Outputs
Wipers
Pegs
Electronic drums provide the benefits of mechanical drums and more. For example,
they have a
preset
feature that is impossible for mechanical drums: The preset
function lets you move from the present step
directly
to any other step on command!
Purpose
Drum Terminology
Summary of Contents for DL05
Page 1: ...DL05 User Manual Automationdirect com ...
Page 2: ...DL05 User Manual Automationdirect com ...
Page 436: ...1B DL05 Error Codes In This Appendix Ċ Error Code Table ...
Page 443: ...1C Instruction Execution Times In This Appendix Ċ Introduction Ċ Instruction Execution Times ...
Page 459: ...1D Special Relays In This Appendix Ċ DL05 PLC Special Relays ...
Page 464: ...1E DL05 Product Weights In This Appendix Ċ Product Weight Table ...