Page 288 - Programmable Logic Controllers, Fifth Edition - Mobile version

Inputs
SW T4:0/DN Ladder logic program Outputs
L1 TON L2
TIMER ON DELAY EN
Timer T4:0
Time base 1.0
SW Preset 3 DN PL1
Accumulated 0
T4:0/DN BSL
BIT SHIFT LEFT EN PL2
File #B3:0
Control R6:0
Bit address B3:0/0 DN PL3
Length 3

R6:0/UL B3:0/0

B3:0/0 PL1

B3:0/1 PL2

B3:0/2 PL3

Figure 12-26 BSL instruction with a wraparound operation.

• Logic 0 in the shift register indicates that the con- • The count obtained by the two counters should be
veyor has no parts on it to be sprayed, and it there- equal when no parts are being painted.
fore inhibits the operation of the spray guns. • Whenever the two counts are equal in value the equal
• Counter C5:1 counts the parts as they enter the pro- instruction executes to turn on pilot light PL1. This
cess and counter C5:2 as they exit. is an indication that the parts commencing the spray-
painting run equal the parts that have completed it.

An example for a bit shift program used to keep track
of carriers flowing through a 16-station machine is shown
in Figure 12-30. The operation of the program can be
summarized as follows:
• Proximity switch 1 senses a carrier, and proximity
switch 2 senses a part on the carrier.
• Clock pulse generated by carrier proximity switch
I:1/1 shifts the status of the data provided by part
detection proximity switch I:1/2.
• When a part and carrier are sensed together, indi-
cated by simultaneous closing of I:1/2 and I:1/1,
logic 1 is input into the shift register at output O:4/0
to energize the pilot light connected to it.
• Remaining pilot lights connected to output module
O:4 turn on in sequence as carriers with parts move
through each station.
Figure 12-27 Cartons traveling on a conveyor being
detected by a photoelectric sensor. • They turn off or remain off as empty carriers move
Source: Courtesy Banner Engineering Corp. through.

Sequencer and Shift Register Instructions Chapter 12 269

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