Siemens Ladder Logic Programming Help Needed.

Hello there, I am currently taking my final year project and working out in my ladder logic programming. I am finding some difficulties on completing the program.

My project is about a rain harvesting machine.
it has only 8 inputs and 6 outputs.
Its a very easy programming but since I am so new i find it hard. Anyone out there can help me please. Your help is really appreciated.

Please email me at [email protected]

Well, first of all let us know what your system is supposed to do, secondly tell us what plc are you working with and finally show us your efforts in order to accomplish what your system needs to do.

Hello there, thank you for your kind reply. my project is like an an smart water system. i will briefly explain the process flow in here below.

First of all the the designed harvester will collect the rain water.

1) Once rain started to fall, container’s lid will open

2) Rain water will fill in the empty container.

3) There are 2 sensors in the container. one is high and one is low. till it reaches high there is no signal sent to close the lid of the container which is controlled by a valve to push it ( open or close). after the water level reaches the high level the lid is closed.

4) there is a Ph sensor located in the container to check the acidity of the water. Next the pH sensor will detect the pH level of the water.

5) there are one more container will be located which will be connected by a valve. in this container there will be nutrient to shoot in so that the acidity of the rain water becomes okay.

i. If the pH is within range of 6.2 and 7, thus no action is required from the nutrient box

ii. If pH is more than 7 and less than 6.2, the valve connecting nutrient box and rain harvester will open, allowing the flow of nutrient; at the same time controller will trigger the mechanism of stirrer. PH sensor keeps track on changes happen on the pH level of water and transmits data immediately to controller. Once required pH level reached, the controller will force the valve to close the flow from nutrient box and the stirrer will stop.

5) Once the rainfall filling reaches ½ the capacity of the container, the ‘Ready to Use’ indicator will flash. At this level of water and onwards the water from container can start to be utilized.
6) Once it reaches max level, second LED will flash, indicating that the container is full; container’s lid will close.

7) Harvested rain water will be kept in storage until there is an input command trigger from human through switch to stop usage of water from utility meter and replace rainfall water for utilization.

8) Timer placed, will be the controlling factor on how much of water volume intended to shower the plants/vegetation.

9) After a period of time the controller will send signal to close the solenoid valve.

ii. If pH is more than 7 and less than 6.2,...

Click to expand...

I think that you meant to type: "If pH is more than 7 OR less than 6.2,.."

First, assign your PLC Outputs. Using the Outputs that do the work, you can develop a quick idea of what programming steps will be needed.

Output 1: Open Lid
Output 2: Close Lid
Output 3: Open Nutrient Valve
Output 4: Close Nutrient Valve
Output 5: Nutrient Stirrer
Output 5: Ready to Use Indicator
Output 6: Container Full Indicator

Then for each Output, ask yourself: what inputs are needed to control this output? What turns it on? At some later time, what turns it off?

Now test out your logic, make corrections, and you are done!

yes. pH is just to be measured within the range of acidic which is around 1 to 3 and alkali around 9 tp 10. the border line or the set off value will be 7.

i am using s7 200 siemens plc with 8/6 I/O pins.

Thank you Lancie. I need some help in the ladder logic part. can u help me

do anyone recommend any other easy softwares to use. i am using step 7 microwin

Thank you Lancie. I need some help in the ladder logic part. can u help me

Click to expand...

Yes, I have a copy of Siemens S7-200 Microwin.

Do you know how to place the above 6 Outputs each on a Siemens network (ladder logic rung)? If so, first do that, so that you have 6 networks with 6 outputs (one output on each network).

Thank you so much Lancie. I will try to work out as i am really very new and i am stuck because i have to submit the results to my lecturer this Saturday. Can u kindly please help me in the construction of ladder logic part if send u the flow chart. I have created a flow chart of my own.

Viviathevan: I do not have siemens software but if you put it in pdf format i can also help you.

Yes Lancie. I did the rungs. but i am not so sure about it. i did studied about latching the whole night and sketched out something. still i found it wrong. My lecturer's do not have any idea on how to construct it.


Can you please have a look at my flow chart.

Dear Widelto, i have my flow chart here. can i email you my flow chart?

Please show it as an attached file.

I am new here. can i know where to attach it?