<Local:1:I.Data.6> Timer_Sw 0 Timer_Sw 10000 Timer_Sw Status_Timer.EN Status_Timer.TT Status_Timer.DN Input L1 Ladder logic TON Timer On Delay EN Timer Preset Accum FBD equivalent TONR_01 TONR ... Timer On Delay with Reset TimerEnable ACC PRE Reset 10000 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 of the BAND block turns false to de-energize the contactor coil and stop the motor. Figure 15-110 shows a comparison between ladder logic and the FBD equivalent for the 10 second TON (ondelay timer) and TONR (on-delay with reset). The operation of the FBD can be summarized as follows: • When the Timer_Sw is closed, the TONR function block timer turns true and starts accumulating time. • The accumulated time is monitored by the output reference tag named ACC. • The EN (enable bit) output changes to 1 to turn on the EN_PL. • The TT (timer timing bit) output changes to 1 to turn on the TT_PL. • The timer times out after 10 seconds to set the DN (done bit) to 1 and turn on the DN_PL and reset the TT bit to zero and turn off the TT_PL. • The EN bit and EN_PL remain on as long as the Timer_Sw stays toggled closed. Status_Timer 10000 0 DN EN_PL <Local:2:O.Data.1> TT_PL <Local:2:O.Data.2> <Local:2:O.Data.3> 0 0 0 0 Outputs L2 EN_PL TT_PL DN_PL DN_PL ACC_Value EN_PL TT_PL DN_PL EN TT DN • Opening the Timer_Sw resets all outputs as well as the accumulated value to zero. • The timer can also be reset by way of the Reset input. Figure 15-111 shows a comparison between ladder logic and the FBD equivalent for the Up/Down counter used to limit the number of parts stored in a buffer zone to 50. The operation of the FBD can be summarized as follows: • The CTUD up/down counter function block accumulated value is initially reset by momentary actuation of the Restart_Button. • The accumulated count is monitored by the output reference tag named ACC. • Each time a part enters the buffer zone, the Enter_ Limit_Sw is actuated and the CUEnable input turns true to increment the count by 1. • Each time a part exits the buffer zone, the Exit_ Limit_Sw is actuated and the CDEnable input turns true to decrement the count by 1. • Whenever the number of parts in the buffer zone reaches 50 the DN bit is set to 1 and the output of Function Block Programming Part 6 391
Petruzella_ProgrammableLogicControllers__5e
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