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How to make a Start Stop Jog circuit in a PLC

Looking at a stop-start jog circuit in the PLC will help us in understanding the differences in hard-wiring the circuit and programming.

Basic Start Stop Circuit

Let’s start with the basic start stop circuit.
Here is what it looks like hard-wired. (Physical switches wired to outputs devices, such as motor contactors and relays.)
Latching Relay Circuit
When the start pushbutton (NO) is pressed the power is passed through the stop pushbutton (NC) to the control relay (CR). The CR contact closes and ‘seals in’  the start pushbutton. The start pushbutton can now be released because the CR contacts allow the power to pass through to the CR.

NO NC Inputs

NO – Normally Open – This refers to the state of the input device if nothing acts upon it. 
NC – Normally Closed – This refers to the state of the input device if nothing acts upon it.

Let’s take a look at the PLC program for the above wiring diagram.
start stop 001
The first thing that you will notice is that the input for Stop is NO contact and not NC. This is because the actual signal wired in the input is NC and we do not want to inverse this signal. You can see that the stop input is currently on in the program.
If we hit the start pushbutton then the circuit is complete and the output CR turns on.

start stop 002Letting go of the start pushbutton, the output remains on because of the CR input seals in the start pushbutton.
start stop 003
Pressing the stop pushbutton will break the circuit and turn off CR.
start stop 004
Letting go of the stop pushbutton will return us back to the original state shown above.

Jog Hard Wire Diagram

Adding a jog input to the hard-wiring diagram will look something like this:
start stop Jog
You can see that the diagram will work the exact same as the circuit above with the start and stop pushbuttons. The jog when pushed will break the sealing contact, and then make a bypass of the start pushbutton. This will keep the M coil on as long as the jog button is pressed. Letting go of the jog will stop the bypass of the start pushbutton which will stop the M coil. When the jog returns to the original state M input will already be off so it will not keep the M coil on.
The action on the jog is referred to as a Break before Make device. The jog pushbutton will break the circuit before making another connection.

PLC Jog Circuit

Sometimes in programming a PLC it can be beneficial to think of the inputs as Make before Break. Inputs are made before the previous ones are broken. The programmable controller will scan the program from left to right, top to bottom. The outputs from the rung above are available to the rungs below. Here is a previous article on PLC scanning.
Lets take a look at PLC program with a jog that will not work.
start stop 010
Even though this looks like it would work… Remember that the contacts in the PLC are making before breaking. You can jog the unit and it will turn on but as soon as you release your finger off of the pushbutton the not jog input will seal the CR in. The output will not be able to turn off.
start stop 011

We must consider the delay from on to off when looking at the PLC program for this circuit.
Here is a circuit that will work:
start stop 020

Notice that we create a delay from on to off by turning on an intermediate bit in the program.

Start Stop Jog using Set and Reset

Another way to do start-stop circuits in the PLC is to use the instructions Set (SET)  and Reset (RST).
The set will have all of the conditions to turn on a bit in memory and the reset will have all of the conditions to turn off a bit in memory. These instructions are used to make the program easier to view and troubleshoot.
Here is the same logic above using the set and reset instructions.
start stop 021

Notice that X10 Jog2 is in parallel with the Start. We use a trailing edge one shot in parallel with the Stop. This sets our delay so the output will turn off.

Watch on YouTube: Learn PLC Programming – Free 4

Start / Stop / Jog Circuit - Learn ...
Start / Stop / Jog Circuit - Learn PLC Programming - Free 4

If you have any questions or need further information please contact me.
Thank you,

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9 replies on “How to make a Start Stop Jog circuit in a PLC”

i have watched a lot of your videos and i still dont get it how to program a plc, whats the best way to get started?

Hi Marcus,
I have created the following link for those that want to start learning about PLCs.
Creating a program can be a little challenging at first. Here is a link from the page about specifically on creating PLC programs.

Developing the PLC program is a process that can be clearly defined. Here is a series that will show you the five steps along with some practical examples.
Five Steps to PLC Program Development
PLC Programming Example – Process Mixer
PLC Programming Example – Shift Register (Conveyor Reject)
PLC Programming Example – Paint Spraying
PLC Programming Example – Delay Starting of 7 Motors
PLC Programming Example – Pick and Place
PLC Programming Example – Sorting Station (Shift Register)
PLC Programming Example – Palletizer

I hope this will help you out.

I’m new to PLC programming and would like to know how do you energize the X1 NO input of the Jog start/stop circuit program using Do-More? I can go to the simulator and turn it on and off, but if I was actually using the program I would want it on (energized) when I started up.

Hi Ken,
If this were connected to a controller, then X1 would be wired to a NO pushbutton switch. However, you can use any internal memory bit that you like to control the program. This includes putting additional inputs to start as well.
If you want the output to turn on when you startup the controller (apply power) then you can use the first scan bit. (ST0 – $firstscan) Put this in parallel to the start input.
The following post has a general overview of all of the memory areas and numbering systems.
I hope this helps you out.

I cannot get the jog switch to work properly on my plc. Start1 and stop1 turns on motor1. Start 2 and stop2 turns on motor2. In order to start motor2, motor1 has to be on. So I put motor1 (no), start2(NC) and stop2 in series to motor2. I parallel motor1 and start2 to motor2 (no). I tried to wire on how u showed in the vid but it did not work. I’ve hundreds of ways but I cannot seem to figure out how to make it work.

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