Bulkhead/In-line Replenishment Snag...

[scolley]

hello1 - your friend's approach sounds fine. Thought about something like that myself. But it does not solve my problem. Your friend still had a float he had to hide. Actually, I had to hide something myself - the little open tube at the bottom of the tank. But a little tube at the bottom should be a lot easier to hide than a float on the surface.

PDX-PLT - Welcome to PT! Great first post too, IMO!

I thought about something like this early one, but could not really get my head around it. You have certainly clarified how something like that might work. Thanks. Good thinking!

This potentially eliminates the deadband problem. Cool! But unfortunately the size of the deadband seems also to correspond to the sensitivity of the pressure sensor. I didn't mention this earlier, but the sensors with large deadband also had large variance between the points they considered "full". So I really abandoned those not only because of the dead band size, but because of their lack of accuracy too.

Sorry. I should have mentioned that. Good solution though!

essabee - Sorry pal. By definition I'm trying to do something hard here. That's why it has its own thread.

[essabee]

Originally Posted by scolley;374249[COLOR="Red"

SNIP[/color]
essabee - Sorry pal. By definition I'm trying to do something hard here. That's why it has its own thread.

....and I thought that you have nearly solved all except getting back to topped-up position and made a suggestion. Sorry man.

[scolley]

OK folks, heads up!

I know I haven't posted my full, functional setup plans. But it WORKS. Works like a charm in fact.

I'm posting now because I just got a notice from Digikey, the only people that I can find that distribute these little water pressure sensors in small volumes. Apparently they are being made obsolete.

So if you want one - get them now. I just bought 5.

Here's a link.

Get 'em before they are gone. At $15 you are never going to see an opportunity like this. I spent a couple of hundred on other sensors before I found this cheap, accurate little jewel. And now apparently they are disappearing.

[scolley]

When I started this thread I was struggling to find a way to top off/refill a tank without putting visible equipment in the tank. And for me, that inlcuded running anything up the side/back of the tank that could be seen.

I experiemented with lots of pressure switches, but only the one from my last post worked well for me.

Here's a pic of it mounted under my tank.



It's a simple contraption really. I have a hole drilled in the bottom of my tank that has the PVC you see mounted under the bulkhead hardware attached to that hole. Above the bulkhead (in the tank) is a simple slip fitting nozzle with a bit of tubing attached. Over that tubing is a bit of hard filter foam. That keeps snails and such from going in the tubing.

Water pressure comes through that nozzle in the tank, through the hole in the glass, into the PVC you see in this picture. From there - as you can see - the water pressure can be detected by the little sensor shown.

The sensor has two wires that close a circuit when it detects a certain level of water. The level can be adjusted with a little trim screw that is just barely visible in the front of the sensor in this pic. It takes a tiny screwdriver.

And it's a PITA to set, because a tiny fraction of a turn of that screw, and you'll change the level of the tank by an inch or two. But once you get it set at the right level, it's solid as a rock.

Anyway, I've got a fill system that first opens a drain (on a soleniod) for a timed period every night. And then a different solenoid opens that allows water from my household tap into my tank lines. This continues on a timer for a set period of time. All that is controlled by an AquaController III.

When this sensor detects enough water pressure to know that the tank is full, the sensor closes the circuit. The two wires you can see in this pic run to the Aquacontroller, which senses the closed circuit. I've got logic in the Aquacontroller that says... "Even if the time to fill the aquarium is not finished, if you see that the circuit has closed, cut off power to the solenoid that's letting water flow into the tank."

Simple really. And the Aquacontroller has a hysterisis function that takes care of my old problem of people walking across the room, making the sensor go haywire if it was near a full condition - with ripples in the surface making it read "on/off/on/off/on/off... " in rapid succession. With the controllers hysterisis function, I've got it set so that if it detect a full condition (possibly caused by someone walking across the room) and closes the circurit, it stays in that closed condition for a full minute before it will turn on again.

A little complicated. But not too bad. And works like a charm - with two mechanisms working together, providing me redundent assurances that I won't over-fill my tank. First - the fill is on the timer I mentioned before. And just in case the fill time is too long, this little beauty of a sensor shuts the fill off if it gets too full anyway.

Problem solved! Automatic water changes every day, and no equiptment to be seen in the tank! Cool.

Thanks for all the help.

[bpimm]

Sweet system,

As I read this thread today I was thinking how to solve your problem, and by the end you had already got there. Great job. the only thing I would have done differently is to have the pressure transducer run the fill valve and reset upon the full state to eliminate the flutter problem. but you got it.

All of my tanks use an overflow and constant inflow to accomplish the same thing, but that requires a standpipe in the tank which is against your goals.

once again, nicely done

Brian

[scolley]

Thanks Brian. And overflow and standpipe (with a sump) will do exactly the same thing. I just got jones for solving the "nothing you can see in the tank problem", and wouldn't let it go until I beat it.

And honestly, I didn't actually succeed completely. I do have a tube that protrudes out of the tank floor, with the bit of filter foam on the open end. It's small, and real easy to hide. But technically it is not "nothing" in the tank. But it seems a small compromise.

Thanks for the feedback!