This can prove handy when you have an application that requires two different cycle times. The preset time of the first timer dictates the OFF time and the preset time of the second timer dictates the ON time. We can develop this code with two ON delay timers and two rungs of ladder logic programming. Both the on and off times are adjustable. It’s basically a two step cyclic sequence based on time. Why? Because, among other things, we can use it to make lights flash on and off. On off timer logic is often referred to as flasher logic. If either of the stop inputs are activated during the ten second starting time, while the siren is activated, then the logic flow to the Siren output is also broken and the siren de-activates. This also breaks the logic flow in the second and third rungs resulting in the motor stopping. If either of the stop inputs are activated then logic flow is broken in the latching logic of the first rung and the Start Command goes FALSE. So when it is TRUE no logic flows and the Siren output goes FALSE and switches off. On the second rung the M1 Run output is normally Closed (NC). So, when the scan gets to the second rung the Start Command is still TRUE and the M1 Run output is also TRUE (the motor is running).

If the stop inputs have NOT been triggered, the Start Command latch will still be active. So, when the PLC scan cycles back to the top and moves through the rungs. That’s not the end of the story, because the siren is still activated. The scan then jumps to the last rung and if the Start Command is TRUE then timer T1 is activated.Īfter the Start Command is TRUE for ten seconds (preset time) the T1 ON delay timer will activate the M1 Run output. Please Note – The M1 Run symbol is triggered from the third rung. If the Start Command is TRUE from the motor control latching logic on the first rung and the M1 Run output is FALSE (motor is not running) then the Siren output is activated.

So now we can use the Start Command latch to trigger multiple actions.Īfter the first rung is scanned it moves to the second rung. The difference is we replace the M1 Run output with an internal variable called Start Command. The first rung works the same as the standard motor control latching logic. Motor Control Ladder Diagram – Delay Start Warning Siren

Contoh kop as built drawing