Neat ATO idea... feedback pls

[curiousphil]

I'm doing some controller planning and a bit of programming today, and I had a neat idea for controlling the ATO pump.

I figure one of the main benefits of an ATO, aside from saving some manual labour, is to keep your salinity stable - right??  And I always measure out my new saltwater carefully to ensure that I keep my salinity stable during water changes.  But what I don't always get right is the water level in the sump - I use the ol' bucket over the top of the tank method for filling... amd even if I used a pump I would still likely want to use all of my makeup water rather than let it sit in a bucket until the next water change or dumping it.

So - instead of using float switches as the primary ATO driver, why not use the data from my conductivity probe?  When salinity reaches 34.95 PPM, turn pump on.  When salinity reaches 35.05 PPM, turn pump off.  This will keep the water level at whatever level I've filled it to while ensuring stable salinity.  I never fill it past the safe level but it is variable enough that if I relied on the float switches to maintain the water level it could cause the salinity to rise or fall from whatever it was right after my water change.

I would still keep the float switches in place as failsafes - if for whatever reason, for example, the conductivity probe reads an OK value but the water level drops past the safe operating level, then the switch would override the probe data.  Likewise if the water level gets too high.


What do you guys think?  Good idea?  Anybody else do something similar to this, or ever heard of it being done?  Foresee any pitfalls or risks that I'm not thinking of?  It would be very simple to code.

 

[Salty Cracker]

You like to make things unnecessarily complex

 

[theyangman]

My ATO draws from a pure RO/DI source and keeps the level in the sump at a consistent level. The salinity therefore doesn't fluctuate very much as the salt doesn't evaporate, the water does so by replacing just pure water it should keep my salinity pretty darn stable. The only thing I have to worry about is maintaining my ATO source. I use a 10 gallon tank beside my sump, and tunze ATO unit. Works flawlessly and salinity has been the least of my worries since going this route and my sump always has the same level of water in it.

During water changes I replace the water back to the same level in my sump and it always has worked for me. But I draw my replacement water from my mixed water storage tank which I carefully maintain at the exact same salinity as my tank.

 

[curiousphil]

You like to make things unnecessarily complex

I like to think of it as fun! lol.  It's easy enough to code for a high switch and a low switch vs using the conductivity sensor.  The data will all be there, it's just a difference of adding in an extra if/else statement.

This ATO will also be drawing from an RO/DI reservoir Tony.  Right now I manually dump in RO/DI water on a daily basis, and when I do my water changes I mix up the water in buckets as I need them.  Hope to build a water change station at some point so that I don't have to worry about leaving unused water in buckets.

 

[theyangman]

[quote author=Salty Cracker link=topic=6519.msg63884#msg63884 date=1381504409]
You like to make things unnecessarily complex

Building one was the best thing I ever did for my tank. Makes water changes about 15 min now. lol

I like to think of it as fun! lol.  It's easy enough to code for a high switch and a low switch vs using the conductivity sensor.  The data will all be there, it's just a difference of adding in an extra if/else statement.

This ATO will also be drawing from an RO/DI reservoir Tony.  Right now I manually dump in RO/DI water on a daily basis, and when I do my water changes I mix up the water in buckets as I need them.  Hope to build a water change station at some point so that I don't have to worry about leaving unused water in buckets.
[/quote]

 

[Neopimp]

conductivity probes are not the most reliable of probes in my experience.... but I am with you on automating stuff for fun / challenge

 

[theyangman]

tada!

 

[Boga]

I think that it is a good idea.

Unfortunately, both kind of probes are prone for failure. Critters can stuck the float valve or can get on EC probe and either create a short or just minimize the area used for EC.

I agree with Neopimp  and I see the EC probes more vulnerable for variation. I would use the float switch as the main control and the EC reading as a safety option. Either way, having a double safety system is good.

Also consider adding a timer to the equation. In my current set-up, I have the ATO pump connected to a timer, set at 6 times per day, so only a certain volume of RODI water can be added into the system. Just little bit more than the average evaporation.

 

[KBennett]

In theory, it would be fun to do, but in practice you'd have issues.  It would only work if your salinity mixed perfectly instantly, or you did your top off extremely slow.  You have no way to know if the salinity at your probe is the same as the rest of your tank.

Next time you add water, monitor your probe to see how long it takes for the salinity to settle down after you stop adding.