Water control circuits for a fountain

[lynx20]

Hi all:

Just stumbled upon this forum and joined hoping to get some help.

I have a fountain at our church that was built from scratch by an artist and I need some control circuitry. One of our members started on the project but his health has deteriorated and he cannot find his schematics. So-

Requirements –
Sense the water level to stop the fountain pump if the water level is too low.
Automatically control a 24vac irrigation valve to fill the reservoir.

Bonus –
LEDs to show which probe is under water.
Shut down the system if water level is too high [fill valve sensor shutoff fails].

Potential issues –
Access to the sensor probes will be under several inches of rock. Therefore maintenance needs to be low [such as ac vs. dc to minimize electrolysis] or good probe designs. This is Las Vegas so 8% humidity and 110+ degrees heat [normal summer] causes evaporation to be critical.

Current resources [partially install parts from previous design] –
110 to 24 v transformer
110 to 12/6 v transformer
7812 voltage regulator
Full wave bridge rectifier
(2) 24v coil relays that can handle appropriate current of the pump & valve.
60 minute mechanical timer [treat as the 110v on/off switch].

I have some experience with electronics. I used to build TTL logic circuits with gate chips, flip-flops, etc. when Radio Shack still had tube testers. Nothing since, so I am very rusty.

Thanks in advance for any help.

Bob

 

[SABorn]

Why use a solonide for the refill/topup, a ballcock float from a toilet system works very, the later designes with the vertical floats are easy to hide in the pond.
A mechanical system is far simpler and reliable over the electricla approach.

Should you want to stick with the solonide, a method i have used is a fill sonsor from a washing machine, as these can be mounted away from the water with a small tube going into the water to sense the pressure of the hydrostatic head.

For the pump if you use a sump pump they have a built in float switch which will turn the pump off when the water level drops too low, so no need for extra electronics there.

I would stay away from probes if you want long term reliability.

The addition of a small float switch to be a fail safe for the water level would be more reliable than probes anyday. (have a look on ebay for float switches lots of them cheap)

Pete.

 

[ADWSystems]

I'm thinking this Velleman kit **broken link removed** could be adapted to do what you need. But I don't have much time this morning to give it much thought. Sorry.

 

[SABorn]

The kit looks good on the surface, but i do really question the long term reliability, and to rely on a circuit like this for an unattended situation i think is risky.

Keep it simple with long proven reliable products would be well worth the effort.

 

[Mike_2545]

Most aquatic (pond) supply stores will have a small auto fill valve, much like a toilet float but easier to install in a fountain.

 

[squishy36]

If you do want an electronic solution, I built a simple float switch 22 years ago (I can remember the date because my wife was pregnant) using a mercury switch and a plastic bottle. I put it on a hinge that lets it rotate up and down. It's just a simple shaft through a plastic bearing (I have a lathe, so I can make such stuff). It has worked reliably and protected our ditch pump from operating when there wasn't enough water in the cistern. I used an old syrup bottle for a number of years and have had to replace the bottles a few times when they rot out. They're held in place by two plastic tie wraps, so they're easy to replace. It might be a bit hokey, but it has stood the test of time. I believe I got the mercury switch from an old thermostat or it was one I bought from Radio Shack.

Of course, it would probably be easier to just buy a commercial float switch -- but I always find it more fun to make things. :^)

 

[lynx20]

Thanks for the quick replies.

I thought about mechanical at first but here are the issues.

1) Fountain is set in concrete pad [part of the design]. Reservoir is under fountain, below grade and not visible.
2) Fill/drain plumbing is already in and is under the concrete & fountain. The irrigation valve is also in place on the edge of the pad - about 9ft [2.75m] away.
3) Access to reservoir and pump maintenance/removal is under several inches of stone. It is a cylinder about 8in [20cm] dia. x 10in [25cm] deep. Clearance is about 1 to 2 in [2.54 to 5cm] total on the sides when removing pump.

Because of this I have to go electronic. A low voltage pvc conduit is in place next to the high voltage conduit used for the pump. Probes can be applied to the wall of the pump access.

And to relieve SABorn's concern - unattended operation of ANY water feature is not permitted by code [unless you are a casino – see Bellagio, MGM Grand, etc.] and is not a factor. Small water features [even 'bird bath' type] technically are not permitted but they are ignored by the water police when placed on a timer [see first post].

Bob

 

[lynx20]

Could you please eyeball the attached? As I stated, I am very rusty on my circuit design - especially non-ttl. I got the idea to use a Schmitt NAND gate from a plant soil moisture indicator. So I 'hijacked' the concept and expanded with some digital logic concepts.

You will see that I am using U1B as an oscillator to generate an ac signal for the probes. My main concern is if I am using the correct logic - positive vs negative.

Any and all opinions will be welcome.

Bob