Page 410 - Programmable Logic Controllers, Fifth Edition - Mobile version

Timer_Sw Ladder logic
<Local:1:I.Data.6>
TON
Timer On Delay EN
Timer Status_Timer
Preset 10000 DN
Accum 0 Outputs L2

EN_PL EN_PL
Status_Timer.EN <Local:2:O.Data.1>
L1
Input TT_PL
TT_PL
Status_Timer.TT <Local:2:O.Data.2>
Timer_Sw
DN_PL
DN_PL
Status_Timer.DN <Local:2:O.Data.3>

FBD equivalent
TONR_01
TONR ...
Timer On Delay with Reset
0 0
Timer_Sw TimerEnable ACC ACC_Value
10000 0
10000 PRE EN EN_PL
0
TT TT_PL
Reset 0
DN DN_PL
Figure 15-110 Comparison between ladder logic and the FBD equivalent for a
10 second TON and TONR timer.

• When the Motor_Stop button is opened the output • Opening the Timer_Sw resets all outputs as well as
of the BAND block turns false to de-energize the the accumulated value to zero.
contactor coil and stop the motor. • The timer can also be reset by way of the Reset
input.
Figure 15-110 shows a comparison between ladder
logic and the FBD equivalent for the 10 second TON (on- Figure 15-111 shows a comparison between ladder logic
delay timer) and TONR (on-delay with reset). The opera- and the FBD equivalent for the Up/Down counter used to
tion of the FBD can be summarized as follows: limit the number of parts stored in a buffer zone to 50. The
operation of the FBD can be summarized as follows:
• When the Timer_Sw is closed, the TONR func-
tion block timer turns true and starts accumulating • The CTUD up/down counter function block accu-
time. mulated value is initially reset by momentary actua-
• The accumulated time is monitored by the output tion of the Restart_Button.
reference tag named ACC. • The accumulated count is monitored by the output
• The EN (enable bit) output changes to 1 to turn on reference tag named ACC.
the EN_PL. • Each time a part enters the buffer zone, the Enter_
• The TT (timer timing bit) output changes to 1 to Limit_Sw is actuated and the CUEnable input turns
turn on the TT_PL. true to increment the count by 1.
• The timer times out after 10 seconds to set the DN • Each time a part exits the buffer zone, the Exit_
(done bit) to 1 and turn on the DN_PL and reset the Limit_Sw is actuated and the CDEnable input turns
TT bit to zero and turn off the TT_PL. true to decrement the count by 1.
• The EN bit and EN_PL remain on as long as the • Whenever the number of parts in the buffer zone
Timer_Sw stays toggled closed. reaches 50 the DN bit is set to 1 and the output of

Function Block Programming Part 6 391

pet73842_ch15_333-394.indd 391 03/11/15 7:34 PM