I need help with 89 State three advantages of using programm

State three advantages of using programmed PLC timers over mechanical timing relays. For a TON timer: When is the enable bit of a timer instruction true? When is the timer-timing bit of a timer instruction true? When does the done bit of a timer change state? For a TOF timer: When is the enable bit of a timer instruction true? When is the timer-timing bit of a timer instruction true? When does the done bit of a timer change state? Explain what each of the following quantities associated with a PLC timer instruction represents:

Solution

Please follow the data and description :

8) TON (Timer On) :

The Timer On instruction is a non-retentive timer that is enabled when the preceding logic is true, and the timer is reset when the preceding logic is false. In the regular usage of the timer this can be compared to a stop watch that is used in the regular life. A value is entered into the preset and an accumulator keeps track of the time. When the accumulator reaches the preset, the timer-done bit is set. The timer-timing bit is set while the accumulator is active. When reset the accumulator is set to 0 and the EN, TT, and DN bits are cleared.

a) EN : Enable Bit, this is set to true whenever an instruction is enabled.

b) TT : Timer Timing Bit, it set to true whenever an instruction is enabled and the respective accumulating time.

c) DN : Timer Done BIT, this is set to true whenever the accumulator reaches the preset time.

9) TOF (Timer Off) :

This is also a non-retentive timer that is enabled when the preceding logic is false, and the timer is reset when the preceding logic is true. A value is entered into the preset and an accumulator keeps track of the time. When the accumulator reaches the preset, the timer-done bit is cleared. The timer-timing bit is set while the accumulator is active. When the preceding logic is true the accumulator is set to 0 and the EN and DN bit are set and the TT bit is cleared.

a) EN : Enable Bit, this is set to true whenever an instruction is enabled and that the TOF is not timing.

b) TT : Timer Timing Bit, it set to true whenever an instruction is accumulating time.

c) DN : Timer Done BIT, this is set to true till the accumulator reaches the preset time.

Hope this is helpful.