Notes

What is Timer in PLC?
Types of Timers
A PLC timer is an electrical system component used in ladder
logic programming. Timers are devices that count time
divisions.
Dr. Ashwin Porwal is a program that controls and operates a device
for a set period. We can use the timer to do any certain
activities for a fixed period.
A timer is one of the most important and helpful entities.
With the help of a PLC programming timer order, you can
build up a time-based action. Each PLC has a unique set of
timer functions.
The timer instruction is used to provide programming logic
and to decide when to switch on or off the circuit. It contains
two types of contacts: normally open (NO) and typically
closed (NC).
On connection or instant disconnection, the timer causes a
delay in both PLC programming and relay boards.
Simply stated, when the input is turned on, the timer begins
to run and keeps track of the time. The timer activates its
output when this time exceeds the programmed time.
In the programming of the Ladder Diagram (LD) PLC, you
could specify the timer from milliseconds (ms) to hours (hr).

Here are some of the key terms to know
about timers in PLCs:

1. Input and Output Modules-
In the PLC system, there are several input (I) and output
(O) modules. They serve as a link between the CPU and
programmable devices. Input Module refers to the
component that interacts with the input signal. It is
necessary to connect input devices such as different
types of switches. Piles refers to the
component that interacts with the output signal. The
output module is necessary for connecting output
devices, such as electric applications.

2. Piles -
The power module supplies electricity to the timing
circuit, which allows it to function properly. It can be
connected to either an ac (120, 230 V AC) or a dc voltage
source (like 5,12, 24 V DC).

3. Internal Timer Circuit-
The set and reset functions are performed by the timer
circuit. The timer will provide the momentary input
pulse for the set and reset operation if the auxiliary
power source is turned on.

4. Timer Digital Display-
The set and elapsed timing values are displayed on the
digital timer. Values can be shown in a few milliseconds
for automated purposes (ms). This will make tracking
your automation system simple.

Different types of PLC timers:
1. On Delay Timer (TON)-
Timers are the most commonly used timer in electric
circuits. You may be familiar with the term "on delay,"
which means "delayed on." It means that the timer will
not update the contacts until the preset time has
passed. These timers are used in Star-delta starter,
capacitive load starter etc.
2. Off Delay Timer (TOFF)-
You may recognize the term "off-delay = delayed off"
from the word itself. This means that even if the timer's
input power is turned off, the timer continues to give
contacts to the exiting circuit.

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