Timers are commonly used instructions in PLC programming, but sometimes we often confuse their functions, resulting in subsequent program debugging or maintenance work. A friend once lost production because he didn't figure out this timer, so he was embarrassed in front of customer leaders and colleagues. In order to avoid friends repeating the same mistakes, the next 5 articles will sort out the functions and uses of these 5 commonly used PLC timers. 

This article will talk to you about the pulse timer Pulse Timer. 

1. Overall working principle 

There is an output when there is a signal (energy stream/RLO, in order to facilitate the understanding of novice friends, and then collectively referred to as a signal), and it is disconnected when the preset time is over; It is also disconnected after the power is cut off. 

2. What it looks like in ladder chart programming: 

Pulse Timer in a ladder chart

In the above figure, the S end is the signal input terminal; The TV side is the preset value input side, which is the timing time you want to set, and 20s is set here; The R end is the reset end; Bl and BCD are output to display the current time value, the display value type is different, Bl is a hexadecimal format without a time reference, and BCD is S5T# format. 

3. PLC programming examples and timing diagram explanations 

Example of pulse timer programming

In the above figure, 10.1 is the start button, the control signal is interrupted, when pressed, the 20s timing starts as shown in Figure 4 below, and there is a signal output (QO.O gets the signal); when the button is released, the output is stopped, and QO.O has no signal as shown in Figure 5 below. When 10.1 is the reset button button (when pressed, the timer output is 0, the stop signal output) is shown in Figure 6 below. 

When the start button is pressed, the output Q is 1

When the input S is 0, the output Q is also 0

When the reset button 10.0 is pressed, the timer returns to 0 (BCD)

PLC timing schematic diagram

The above is the timing schematic diagram of their counterparts. In order to help friends deepen their impression, here I leave you two small questions to think about: When the PLC timer is halfway through, release the start button io.l, does the timer stop output? When the timer stops halfway (IOS), when there is a start signal again, does the timer start from the beginning (20s) or from the middle (IOS)?

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