Chemical dosing pump

[koloyewo]

Can anyone help me with this project(chemical dosing pump) using logo siemens software:

When you press the start push button, it should actuate a solenoid valve and a flowmeter and discharge 98litres of water into tank A, and also actuate another solenoid valve and a flow meter and discharge 2 litres of chemical into tank A. when the low level sensor in the tank A is activated, the counter should reset back to zero and start the process all over again.

The components: A start push button, stop push button, high level sensor and low level sensor in tank A, a flow meter and solenoid valve for water, a flowmeter, solenoid valve and pump for chemical, a low level sensor in the chemical tank.

i have written the program using ladder logic, but how do i control my counter to stop the water valve, after the counter counts 5 times

[drbitboy]

Welcome to the forum!

I assume the Start and Stop inputs are momentary buttons; is that correct?

If the Start button is pressed when Run is 0 (off), should a dosing cycle start if the low level sensor is not active i.e. if the level is not low? Where is the low level sensor in the ladder logic shown?



What does a count of 5 indicate? If the Tank A level goes from low to not low, so that I4 transitions from 1 to 0, will the current logic allow the counter C001 to keep counting?

What should happen when the tank A high sensor becomes 1?

Does the water flowmeter generate a pulse after a certain volume of water passes through the water flowmeter? If yes, what is that certain volume?
In the ladder logic shown, where is the input from the chemical flowmeter, which flowmeter was mentioned in the description? What volume of chemical triggers a pulse from the chemical flowmeter?

In the ladder logic shown, after each scan cycle ...

• Can M2 ever have a different value than M3?
• Can Q1 ever have a different value than M2?
• Can Q2 ever have a different value than M3?

Do you know what a scan cycle is?

[parky]

I agree with DR: need more information, however, there are a number of things that you have sort of duplicated for example the two memories for the Water & chemical you have a not high level sensor in each branch this is not required just one & then parrallel the two memories, you also need a latch for each dosing operation.
I do not have Logo software so here is a simple dosing idea perhaps work on this basis, there are many ways of doing this so this is just an idea should easily translate to logo, I'm not sure they have rising or falling edge trigger contacts (ones with the up/down arrow in the contact) but I assume it should have or you could create a osr with simple logic.

[drbitboy]

@koloyewo still needs to answer the questions posed.

Originally Posted by koloyewo

how do i control my counter to stop the water valve, after the counter counts 5 times

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There is still a problem: flowmeter pulses will not be counted while the low level signal is 1. The fix may be to add a Break (Normally Closed) Contact in series with the low level contact into the R pin of the counter. That Break Contact's operation could be either the Q1 (or Q2) bit so the counter cannot be reset when dosing, or a bit that is 1 when C001 is 1 so the counter cannot be reset whenever it is not expired.

[koloyewo]

Hi all, I am really impressed by the quick response I got from this forum, your responses made me feel more confident about my knowledge in PLC automation.

Back to the questions raised, I will re-explain the project again in more details.

Chemical dosing pump

NB:
--The water is only controlled by a solenoid value, it has a constant supply
--The chemical is controlled by a pump and a solenoid valve
-- Both being controlled by 2 digital flow meters(using pulses) connected in series with the solenoid valves
-- There is a main tank A, that collects the both the water and the chemical
--Tank A has a high level sensor and a low level sensor

Now explanation of the control process:

When the push start button is pressed, everything is turned on (2 solenoid valves, 2 pump, 2 flowmeters), the flowmeter uses counter to control the amount of liquid through the pipe, and when the counter reaches its preset value it changes state and deactivates the pump, solenoid valves. This process stops until the low level sensor actuates and reset the value to 0, and the solenoid valves and pump starts all over again. I used the 5 as the preset value for the counters for simulation purposes.
I have redesigned the the program, and simulated it and it worked. You can give me your ideas on how to do it better and be more logical and presentable.

Thank you

[koloyewo]

here is the screenshot of the program

[koloyewo]

here is a bigger picture but the last part is cut off

[drbitboy]

When Q2 transtions from 0 to 1, does that close the the Water solenoid valve?


Where is the output to the Chemical solenoid valve?

[koloyewo]

Q2 is the water solenoid valve, which is turned on when the start push button is pressed. M2 is the virtual memory connected to the the output of the counter as a coil and also connected in series with the water solenoid valve, which changes states from 1 t0 0 and turns off the water solenoid valve.
Ohh sorry, the chemical valve is controlled by the pump and not chemical solenoid valve( my error)

[drbitboy]

Originally Posted by koloyewo

... give me your ideas on how to ... be more logical and presentable.

Add text comments to the right of each rung, to say what that rung is doing. E.g. the first rung could have a comment "Start or Stop the process running in automatic mode. The C001 counter block rung could have a comment "Reset water dose counter when the level is low; count water dose pulses from flowmeter.

The names or comments on the memory tags do not need to start with "Memory for" - they are already M tags, so anyone looking at the program should know that they are memory tags.

Use multiple line for long tag names so those long tag names do not overlap with the tag names on adjacent blocks.

M1 "Start process" would be better named "Run process" or even "Auto mode."

The logic does not need M2 (Memory for water solenoid valve) or M3 (Memory for pump). C001 can be used on the rung that writes a 0 or 1 output to Q2; C002 can be used on the rung that writes a 0 to 1 output to Q3. That removes two rungs, which increases clarity.

The counters should be named e.g. C001 could be named "Water does complete" and C002 could be named "Chem dose complete."

Perhaps the counters should reset when M1 is 0 (i.e. process is not running in auto mode).

The process will miss water and chemical pulses as long as the low level sensor input is 1; this should be fixed by sending the low level sensor input through a rising edge detector.

[koloyewo]

Please how do I add rising edge detector to the input of the low level sensor, I cant find it in the logo software. Thank you

[drbitboy]

&edge

[koloyewo]

Please help me check this

[koloyewo]

Also, I want to upload my program to siemens logo but it cannot connect to remote device. Please help me

[drbitboy]

Originally Posted by koloyewo

please help me check this

The C001 and C002 contact should be inverted, and be gated with the Started bit, so the pumps and valves will dose until the count is complete.

I assume I6 is the low level that restarts the next dosing.

Also, there is no high level logic that should perhaps stop the dosing.

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