Twidosuite Timer & Delay Problem

Hi I am using Twidosuite for Schneider Electric TWDLMDA20DRT base controller.
Some problems with the rungs as I am still beginner and been trying hard to get the answer.

I have a cold water and hot water system running at the same time.
For best comfort, hot water is injected at 20% of cold water.
In other words, Hotwater = 0.2 Coldwater

However, when the cold water flow increase by 50%, the hot water has to increase too. BUT, with a lag time of 10 min, in order not to stress the pump and sth else blah blah blah.

For example, at 13:15, cold water is at 10 litres/min, and hot water is at 2 litres/min.
But at 13:16, the cold water increase to 18 litres/min, so hot water has to increase to 3.6 litres/min.
But the increase of flow for the hot water can only starts 10 minutes later, which is at 13:26.

If given a stipulated or scheduled time everyday, it will be easy.
However, the increase of cold water flow may be sudden any time and hence I am clueless on how to derive a PLC rung for such circumstances.

Any help? Thanks.

I think you are saying the hot water control should have a 10 minute lag time in it control. This would be easy to implement in a more powerful processor (M340 for example) that has a Lag function built into its control library. In your case you will have to build a delay using a FILO (first in last out) stack. Start with a say 10 word array, then every minute move the array along 1 (Array_8 to Array_9, Array_7 to Array_8, etc) and move the cold water flow into the start of the Array (Array_0). Then you use the tail of the Array (Array_9)as the control for your system

Thanks Geoffc.

Thats a great way too. I was planning to use a timer of 10 min though, which will activate the increase of hot water flow.

However, what I could not achieve now is letting the PLC know that for there is a change in cold water flow, which could happen in a short span of 10-15 seconds.

This is what's troubling me. Thanks.

you have to copy cold water flow to memory, then on next plc scan (or after short time delay) compare old saved water flow to flow from analog input.
Raise bit up if flow is bigger or less than old flow (you probably need some hysteresis also for this, because analog signal (raw data) is jittering little bit even on constant flow)

Where to buy in Singapore? urgent

Hi guys,

I need urgently 1 pc. Schneider TWDLMDA20DRT

you know where I can find this ready in stock, in Singapore?

Thanks in advance for the help.

Joao

Hi joao, google Lim Kim Hai or New Prosperity Electric.

Hi Lare, thanks for the reply.

I still have a question.

I have to add a small amount of hot water of 1 litre (e.g. %MF100) every 15 minutes until it reaches a certain required flow, maybe say 10 litres for example.
However the increment can only be 1 litre.
What can be the rung design be?

dwpang said:

Hi Lare, thanks for the reply.

I still have a question.

I have to add a small amount of hot water of 1 litre (e.g. %MF100) every 15 minutes until it reaches a certain required flow, maybe say 10 litres for example.
However the increment can only be 1 litre.
What can be the rung design be?

Click to expand...

You allready know it and writed it

add/subtract one litre every 15mins (rising edge of timer) when needed?