We have discussed many PLC ladder logic examples on our blog and in this article, we are going to see another example of lamp control. To understand this concept, we have taken the example of lamp control that will be controlled by making use of timers.
PLC timers are internal PLC instructions that are used to delay input and output signals in the PLC program.
In this article, we are going to see how to draw a ladder logic diagram of lamp control using PLC timers. One should note that these are the basic examples of PLC ladder logic examples for PLC ladder logic practices.
More examples of lamp control along with its solutions are discussed in Example 1 and Example 2.
Lamp Control Using Timers
In this ladder logic example, we will see how to draw a ladder logic diagram for lamp control of a system using on-delay timers.
Problem Statement
Draw a ladder logic diagram to control the lamp output as per the given logic. Make use of On-Delay timers for this problem.
- Start the system using the start push button.
- Timer T1 receives an impulse from system memory to give outputs (lamps L1 and L2) after 2 seconds.
- Timer T2 receives an impulse from system memory to give outputs (lamps L3 and L4) after 4 seconds.
- Timer T3 receives an impulse from system memory to give outputs (lamps L5 and L6) after 6 seconds.
- Timer T4 receives an impulse from system memory and turns OFF the lamps L1, L3, and L5 after 8 seconds.
- Timer T5 receives an impulse from system memory and turns OFF the lamps L2, L4, and L6 after 10 seconds.
- Timer T6 receives an impulse from system memory and turns ON all the lamps after 12 seconds.
- Timer T7 receives an impulse from system memory and turns OFF all the lamps after 14 seconds.
Write down a ladder logic diagram for the above problem statement.
List of Input and Output Tags of Lamp Control
In this PLC ladder logic example, we have used one input, 7 T-ON timers, 5 memories, and 6 lamps.
| Address | Description | Type |
| I0.0 | START PUSH BUTTON | INPUT |
| M0.0 | CYCLE ON/OFF MEMORY | MEMORY |
| M0.1 | STOP MEMORY | MEMORY |
| M0.2 | MEMORY FOR L1, L3, L5 OFF CONDITION | MEMORY |
| M0.3 | MEMORY FOR L2, L4, L6 OFF CONDITION | MEMORY |
| M0.4 | MEMORY FOR ALL ON CONDITION | MEMORY |
| Q0.0 | LAMP L1 | OUTPUT |
| Q0.1 | LAMP L2 | OUTPUT |
| Q0.2 | LAMP L3 | OUTPUT |
| Q0.3 | LAMP L4 | OUTPUT |
| Q0.4 | LAMP L5 | OUTPUT |
| Q0.5 | LAMP L6 | OUTPUT |
| DB1 | T-ON TIMER 2 SECONDS | TIMER |
| DB2 | T-ON TIMER 4 SECONDS | TIMER |
| DB3 | T-ON TIMER 6 SECONDS | TIMER |
| DB4 | T-ON TIMER 8 SECONDS | TIMER |
| DB5 | T-ON TIMER 10 SECONDS | TIMER |
| DB6 | T-ON TIMER 12 SECONDS | TIMER |
| DB7 | T-ON TIMER 14 SECONDS | TIMER |
Ladder Logic Diagram of Lamp Control using Timers
In this PLC ladder logic example, we have used Siemens S7-1500 PLC and Siemens TIA portal for programming a ladder logic diagram. The PLC we selected has a work memory of 250 kB, 24 V DC power supply with 24V DC 32 digital inputs, 16 digital outputs, 4 analog inputs, and 2 analog outputs on board.
For simplicity of the program, we have divided the program into 3 networks.
Network 1
It is the cycle Start and Stop network. Start Push Button (PB) is used to start the cycle.
A Normally Closed (NC) input is taken for Stopping the cycle. A Normally Open (NO) input is taken to start the cycle. A memory (M0.0) is taken that will be used in further networks. This memory is latched to the Start PB.
The cycle is started by pressing START PB (I0.0).
Network 2
It is the main program network that contains 3 timers and 6 output lamps. Timers DB1, DB2, and DB3 are connected in parallel with each other. Each of these timers has 2 outputs in series as shown in the figure below.
Working of Network 2
- Timer DB1 starts counting its preset time of 2 seconds after pressing the start push button and gives an output signal to the lamps L1 and L2.
- Timer DB2 starts counting its preset time of 4 seconds after pressing the start push button and gives an output signal to the lamps L3 and L4.
- Timer DB3 starts counting its preset time of 6 seconds after pressing the start push button and gives an output signal to the lamps L5 and L6.
- When the MEM1 from network 3 activates, lamps L1, L3, and L5 turn OFF.
- When the MEM2 from network 3 activates, lamps L2, L4, and L6 turn OFF.
- When the MEM3 from network 3 activates, all the lamps turn ON.
- And when the MEM4 from network 3 activates, all the lamps turn OFF.
Network 3
Network 3 is the timer memory network. In this network, 4 T-ON timers are used to solve the problem.
Timer DB4 gives output MEM1 after 8 seconds, timer DB5 gives output MEM2 after 10 seconds, timer DB6 gives output MEM3 after 12 seconds, timer DB6 gives output MEM4 after 12 seconds, and timer DB7 gives output MEM2 after 14 seconds.
These memories are then further used in network 2 for lamp control purposes.
