My automatic water changer system concept
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Old 08-15-2007, 05:41 AM   #1
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My automatic water changer system concept


Hi,

Reading many of the posts on this site (especially Scolley's) has inspired me to plan an auto WC system for my planned living room tank. This is a description of what I'm thinking of doing. Comments are welcome.

Some initial criteria:

-- I'm on well water; no need to worry about dechlor.

-- I'd like to minimize pipes going into the tank, but I not going the drilled tank route. But I'd like to use the filter intake and outflow pipes.

-- At the same time, I didn't want to put anything restrictive in the path normally used by the filtering system; that rules out most reasonably-priced solenoid valves.

-- I was first planning on running two pipes down to the laundry room, one for drain and one for fill. Then I realized they're never used simultanously, so I could run one fairly large diameter pipe (maybe even 1/2") and use it alternately for draining and filling.

-- I'll have a glass top, so I can hang level switches from it.

OK so here is the concept:



At the top are two liquid level switches used to determine the "Full" water level, with output signals Full-1 and Full-2. I use two for redundancy, since this is a very important function to prevent flooded floors.

Water can be drained from the tank by turning on the drain pump, Valve-1, and Valve-3. Water can be put into the tank by turning on Valve-2 and Valve-4. These four valves can be relatively inexpensive diaphram valves, as the drain pump and fresh water supply provide substantial pressure.

The check valve prevents any chance of the drain pump draining the canister filter and causing it to lose prime. This is a big check valve with 1.25" inputs, and a CV factor of 190(!). At 5 GPM flow, the pressure drop through it is 0.03 PSI. The valve also means there's no concern that the fresh water supply, when in Fill Mode, will flush crud out of the filter and back into the tank. This is a picture of the check valve and one of the subminiature level switches, with the Coke can for scale:



The adjusting valve can be used to reduce the flow from the fresh water supply in Fill Mode. I may also need an auxiliary heater to warm up the incoming fresh water: "back of the envelope" calculations show that with the one 300W Hydor inline heater in the system, I can only put in 1 gallon every 4-5 minutes. To up that, and be able to keep the water warm, I may need to turn on an auxiliary heater.

All of this is going to need some type of controller. The plan is that when the WC controller receives a trigger signal, from a timer or perhaps a PC application, it will start a drain/fill cycle. The following would then occur:

-- The tank is normally in an "overfill" condition; i.e., filled to a level a little above that needed to turn on the level switches.

-- When the Trigger signal is received, the WCcontroller first checks that both Full-1 and Full-2 signals are True. If either one is False, the controller turns on an alarm (now just a buzzer, but eventually could send and SMS message to my cellphone), and stops.

-- If Full-1 = Full-2 = True, then the controller drains out some water for a short time T1. T1 is long enough to guarantee that both level switches go to False if they are operating properly.

-- At the end of T1, if either Full-1 or Full-2 are still True, the alarm is turned on, and draining is turned off.

-- Otherwise, we know at this point that, fairly recently, both level switches read True when they were supposed to, and they both later read False when they were supposed to. So we can have confidence in them to proceed further. Draining continues for a period T2, which is chosen to be long enough to drain the desired amount.

-- At the end of T2, the controller stops draining and, after a brief pause, begins filling. It also starts timing a period T3. T3 is timed to be long enough to guarantee that the level switches will go True: in other words, if they don't both go true by the end of T3, something is wrong.

-- When either Full-1 or Full-2 go True before the end of the T3 period, the T3 timer is stopped, the controller continues filling, and starts a brief timer T4. If T3 expires before either Full-1 or Full-2 going true, then filling stops and the alarm is set. This prevents flooding the floor if both switches malfunction.

-- At the end of T4, filling stops, The tank should be in the proper "overfill" state now. If either Full-2 or Full-2 are still False, the alarm is set.

So I still have a bit of work to do. A design for the controller based on an Atmel AT89S51 microcontroller is here:



I included relays to turn the canister filter and the inline heater on and off as well, in case I need to. I also added switches to manually put it in either Drain or Fill mode. A 24 VAC power supply is included that can be used to operate the 4 valves. I got the PCB board design pretty much done. Now if I can just find the code to the last 8051 microcontroller project I did about 12 years ago, I'll have a jumpstart on doing the code.
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Old 08-15-2007, 06:09 AM   #2
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cool.
I was thinking of doing the same but I have to dechlor my water supply and I have no Idea how that can be done accurately.

Maybe you can save $$$ on not buying a drain pump and do like this?
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Old 08-15-2007, 11:53 AM   #3
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can you get away with using the filter as your pump for the drain line?? In other words, move the drain to the outfow of the filter and just have a by-pass switch that turns either the return line to the tank and drain line on/off? Or if you can get away with just the head pressure from the siphon of the tank, you could just drain it without a pump. Be sure to have the filter turn off though!!!!

with all those controllers, what happens if you have apower outage during the drain process? Are they powered switches that will turn off or close when there is no juice?? Same with the floats i guess too.

Here is a link to another water changer system using X10 controllers instead of a processor.

http://www.plantedtank.net/forums/eq...ger-setup.html
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Old 08-15-2007, 01:53 PM   #4
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You can also use an overflow box, like the ones they use for a sump system, then you drill that and set the water level in it with an overflow drain. then regulate your incoming pressure and use a needle valve to control the fresh water. always topped off, no electronics. can still add the float switch to a valve on the incoming water in case the overflow plugs or looses the siphon.

But then if you want the electronics that's a cool project by it's self, I've always been a fan of simplicity. and I know my experience with commercial electronics leads me to not want them involved in keeping the water in my tank.

The reliability of your own design may be better tho.

I know that gravity hasn't had any downtime so far, at least to my knowledge.
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Old 08-15-2007, 05:45 PM   #5
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Quote:
Originally Posted by mistergreen
Maybe you can save $$$ on not buying a drain pump and do like this?
Quote:
Originally Posted by gmccreedy View Post
can you get away with using the filter as your pump for the drain line?? In other words, move the drain to the outfow of the filter and just have a by-pass switch that turns either the return line to the tank and drain line on/off? Or if you can get away with just the head pressure from the siphon of the tank, you could just drain it without a pump. Be sure to have the filter turn off though!!!!
I thought of doing that, but I think in order to get good flow on the drain line that's predictable, and doesn't require a pump anyway as you did, it requires putting a valve in the return path from the filter (it's a long way to the laundry room). Solenoid valves with high CV factors that won't unduly restrict normal filter operation are very expensive; more expensive than a utility pump.

Quote:
With all those controllers, what happens if you have a power outage during the drain process?
It's just one common controller. If it loses power, the relays will get to a state where the valves are closed, the drain pump is off, and the filter and heater get power (assuming there's still power in the house).

Quote:
Here is a link to another water changer system using X10 controllers instead of a processor.
Yes I saw that; it was one of the inspirations for this work.

Quote:
Originally Posted by bpimm
But then if you want the electronics that's a cool project by it's self, ...
Yep, I'm a natural tinkerer (alot of folks here seem to be), and didn't want to go the drilled tank route this time.

Looking it over, I think I'll need to make a slight modification: When closed, Valves 1, 2, and 4 experience reverse pressure. This will pop open cheap diaphram valves, so I'll just need to add some cheap check valves on each of their outputs.
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Old 09-01-2007, 04:29 PM   #6
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Very nice setup PDX-PLT! I hope you build this, as I'd love to see the results.

A couple of comments:

1) The use of a single PEX line for drain and fill is ingenious. But the problem I see with it is that your 4 valves are all going to have to be controlled by the same controller. So one way our another, you are going to be running not only the PEX, but also the power/control wires for the valves. If you just simplify this and run two PEX lines (one drain, one fill), it will be less clever, but you can reduce this down to 2 valves, and not have to run electrical wires along with your PEX.

2) I initially used a pump as you are. But I'm not using PEX tubing, I'm just using 1/4" tubing. The pump was nice, because it gave a nice predictable flow rate. Problem was, I found, was that the flow was no faster with the pump than without. The friction of a very long run of 1/4" tubing was so significant that both using no pump - just the head pressure of the water - and using the pump peaked out at just the same rate. So the pump did little good. But in your case, that PEX is larger diameter (I assume) so you may find the pump brings value. I look forward to finding out.

Good luck! Go for it!
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Old 09-04-2007, 10:07 AM   #7
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Quote:
Originally Posted by scolley View Post
Very nice setup PDX-PLT! I hope you build this, as I'd love to see the results.
Steve -

Thanks for the kind words. Some vacation time has allowed me to make some progress on the controller.

I found a great system for making homebrew PC boards. It uses laser printer toner printed on a special paper with a water-soluble coating to make etch resist patterns. The little company that sells the paper is www.pulsarprofx.com (I have no affiliation with them). Some thumbnail pics:



In the first, the backside trace pattern is printed out on my ancient HP Laserjet 4P. In the second, the toner's been heat-transferred to the PCB by running the board and the paper through a laminator, and then placed in a water bath to release the paper. In the third, a green sealing layer that heat-fuses to the toner has been attached by running the board through the laminator again with the green film, and in the fourth the uncovered copper has been etched away by putting the board in a nasty chemical.

More pics:



The fifth pic shows the copper traces left after the green film and the toner's been removed. The next pic shows the top side, which is mostly ground plane. In the seventh pic I've used the toner transfer again to label the top of the board as to which components go where, and label the connectors. The last pic shows the components all installed.

Now I have to write a little bit of 8052 assembly language; it's been about 15 years since I've done any of that.


Quote:
A couple of comments:

1) The use of a single PEX line for drain and fill is ingenious. But the problem I see with it is that your 4 valves are all going to have to be controlled by the same controller. So one way our another, you are going to be running not only the PEX, but also the power/control wires for the valves. If you just simplify this and run two PEX lines (one drain, one fill), it will be less clever, but you can reduce this down to 2 valves, and not have to run electrical wires along with your PEX.
I'm not at all concerned about running some low-voltage wiring in parallel with the tube (I'm using 24V valves). It's small, flexible cable that's easy to run. Worst case, I could always use something like Insteon or Z-wave or Zigbee to control them remotely. Either way, it's easy to me than running water lines.

Quote:
2) I initially used a pump as you are. But I'm not using PEX tubing, I'm just using 1/4" tubing. The pump was nice, because it gave a nice predictable flow rate. Problem was, I found, was that the flow was no faster with the pump than without. The friction of a very long run of 1/4" tubing was so significant that both using no pump - just the head pressure of the water - and using the pump peaked out at just the same rate. So the pump did little good. But in your case, that PEX is larger diameter (I assume) so you may find the pump brings value. I look forward to finding out.
I'll just need to experiment with/without the pump once I get it set up. The water drains down to a room one floor downstairs, so I could very well end up being in the same situation as you and not needing the pump; if I need it I've made provisions for controlling it.

I'm planning on running 1/2" pipe, same as most plumbing pipe, which has 4x the cross-section of 1/4" tubing. I could just use black polyethylene, but I'm going with the cross-linked polyethylene (PEX) that plumbers use since it's alot tougher, it's going to be buried in a wall, and it's still pretty cheap.

Quote:
Good luck! Go for it!
Thanks for the encouragement and the input.

--Barry
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Old 09-04-2007, 11:09 AM   #8
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thats not just tinkering bro...thats just insane cool. way to go....I am so psyched to see this thing in its final setup.

I got my fingers crossed that it works out for you.

Is there a way that you can run testing or diagnosing on the board you made to make sure it works before going all the distance to completion?
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Old 09-04-2007, 12:26 PM   #9
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Barry, OK, I am seriously in awe, and subscribing to this one.
I can't wait to see how this turns out.
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Old 09-04-2007, 05:16 PM   #10
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how to make your own pcb
http://www.youtube.com/watch?v=urv6jArKp6M

you can use regular photo gloss laser paper.
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Old 09-07-2007, 06:19 AM   #11
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The video sums up the process. Conventional wisdom is that the particular Staples brand glossy paper works much better than others. Even so, the glossy paper is much more difficult to use than the Pulsar paper. The Pulsar paper is about $1.40 a sheet, though.

Quote:
Originally Posted by gmccreedy View Post
Is there a way that you can run testing or diagnosing on the board you made to make sure it works before going all the distance to completion?
Yep. I downloaded a little program to the board; it simply turns on the buzzer when any of the inputs are closed (this actually tests most of the board's circuitry). It worked just fine!

Further updates won't happen for awhile; not until I get the tank set up. This means I need to finish the stand (back to woodworking). It's taking a while.
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Old 09-09-2007, 04:35 PM   #12
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That pulsarprofx is cool!!
Oh, and your project is really awesome too!
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Old 09-21-2007, 10:40 PM   #13
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Seems excessively complicated to me, ok I'm hooked, can never get enough of the extremely overengineered..
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Old 11-04-2007, 01:00 AM   #14
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Update: I got the Controller Hardware all finished.

Here is a clickable thumbnail of the interior:

Here is the front panel:

Here is the back panel:

I put two AC inlets in the back since some of the things I may potentially want to control, like the filter, I may want to put on a UPS. But other things like heaters would drain a UPS quickly.

My LFS had a sale on big (>=75 gallon) tanks, so I picked up a 90 gallon. It's sitting out in the workshop and serves as motivation to keep going on this project. Unfortunately I was gone half of last month on business, and I'm gone next week as well. But I'll keep plugging away at it.
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Old 11-04-2007, 01:36 AM   #15
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Holey Moley! I am humbled by this! That is particularly true because I don't even know what I'm looking at!

You've clearly done a great job at constructing something tightly configured to your needs. Job well done Barry!

But please, do explain what we are looking at, in particular with reference to your 1st post on in this thread. I'm trying to relate all the connections in the back of your box, and relating them to what you were originally trying to do, but I'm not comprehending all the connections. Can you please explain?


PS - I don't want to hijack the subject of your thread... but I do want to mention that I am thrilled that you are trying to take a practical and affordable approach to auto-water changing without unusual tank modifications. While I may have executed a proof-of-concept, but you are executing a far more valuable real world "you can build this yourself" alternative. Most people are NOT going to drill their tanks, and you a blazing making significant contributions to making auto water changing accessible a larger audience. Thank you.
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