Cyclic Timer

[USFguy]

Hi,

We are using a ProFiLux3ex in an environmental engineering laboratory as the brains and senses for a sewage treatment machine prototype. No fish, no aquarium. Yes, I know it's weird. We are having trouble programming a "backwash cycle," which will backwash our membranes for a 20s pulse, when our fill tank has been emptied of sewage from the last run cycle and before the sewage tank is refilled. Here is what we have:

Filling cycle
S1 = Sewage filling pump set to G6
G6 = G5 Delayed on 60s
G5 = Water Fill 1 and Timer 1
Water Fill 1 = Min/Max (level sensors to fill tank with sewage to be treated)
Timer 1 = 0000-0100 and 1200-1300
This works fine. S1 starts filling the emptied tank at the right times and after the 60s delay. We put in the 60s delay to allow the backwash cycle to commence only right before filling and if there is now sewage in the tank

S6 = Backwash pump set to G8
G8 = G5 AND Timer 2
G5 = Water Fill 1 and Timer 1
Water Fill 1 = Min/Max (level sensors to fill tank with sewage to be treated)
Timer 2 = switch on 1 after 10s to 10s
switch off 1 after 20s to 20s
switch on 2 after 3600s to 3600s
switch off 2 after 1s to 1s
This is not working. S6 never fired on. We started experimenting with 10s, 20s, 30s, 40s and used a stopwatch to try to figure out how the cycles are working. I think the cycle starts at the bottom and goes up i.e. it was trying to do 1s on, 3600s off, 20s and 10s off versus the the top-down order, that would explained why we never observed a backwash before filling started. also we would try to break the cycle in the middle of (10s into) the the 20s on period by toggling the min/max levels. When the cycle resumes, we think it restarts in the sub-cycle where it left off BUT starts that sub cycle over. When we broke the 20s on sub-cycle by elevating the min/max levels and let them fall, S6 came on for 20s

Does cyclic timers operate in a top-down or bottom-up order?
Do cyclic timers resume in the sub-cycle in which they left off?
if so? do they start that sub-cycle over?
can we get cyclic timer to only cycle once? Because the 3600s off is intended to effectively stop backwashing after a single 20 cycle?
Does anyone have a better method to approach these issues?

Thank you very much for your consideration and assistance.

Sincerely,
USFguy

[Antipodes]

OK many things going on here, but I think I have what you are trying to achieve.

First the order of operation in cyclic is topdown! (there is a delay on switching which is about 2 to 3 seconds I notice when testing, which may have skewed your timings)

So in your case you are
switching on 10 secods after fill start
Switcing off 20 seconds later
1 hour later it should turn on, but your other timer is disabled by then, so it will not action.

Yes if you interrupt the cycle, it will return to Zero and restart the cycle.

And no, Cyclic timers are by nature cyclic and will continue indefinitely if it meets its prerequisites.

"We put in the 60s delay to allow the backwash cycle to commence only right before filling and if there is now sewage in the tank"
I presume this is meant to read NO sewage in tank?

Personally I think you are better off using a standard timer to achieve what you want.

S6 = Backwash pump set to G8
G8 = G5 AND Timer 2
G5 = Water Fill 1 and Timer 1

Timer 2 = Short switching set on: at 1200am for 20s, and 1200pm for 20s.

[USFguy]

Dear Paul,

Thank you very much. Your solution is working beautifully. The manual is a little vague, and it seems to have been translated from Deutsch into English. I must have glanced over the short timers not realizing there significance. To be fair, I thought I was after a cycle, and I didn't explore my alternatives well.

I have since increased my filling and backwashing to 10 cycles per day. I had to link two timers with the boolean OR in programmable logic. For example:

For Filling Cycles
Timer 3 = 00:00 - 00:24
(Morning) 02:24 - 02:48
04:48 - 05:12
07:12 - 07:36
09:36 - 10:00

Timer 4 = 12:00- 12:24
(Night) 14:24 - 14:48
16:48 - 17:12
19:12 - 19:36
21:36 - 22:00

G10 = Timer 3 OR Timer 4
G5 = Water Fill 1 and G10
and again
G6 = G5 Delayed on 60s
S1 = Sewage filling pump set to G6

Timers 5 and 6, the backwash timers, have the same start times as 3 and 4 but they are short timers that run for 20s.
I've just added these timers in the last hour and hopefully they run smoothly with the OR logic both day and night.
Any other advise or suggestion from Paul or anyone else would be greatly appreciated. Again, thank you, Paul.
I hope this thread will be helpful to others ProFiLux users in the future.

Sincerely,
USFguy

P.S. "I presume this is meant to read NO sewage in tank?" Yes you are correct, Paul. That is a typo. I should have proof-read. There should be NO sewage in the tank during backwashing or bad things could happen.

[Antipodes]

I am not sure on how the sewage is actually removed?
I am guessing it is gravity feed as you have no other code or instructions included here.

If you find that the timer system works well, then I would probably be happy enough with that.
But if your trying to maximize the amount of cycles that the system can do. Then perhaps using a couple of level sensors may work better for you.

But as I am not sure on your whole system lay out, it is a bit hard to make a solid suggestion.

Don't worry about the dear bit mate, you don't know me well enough to be dear to me!!:)