Backyard Aquaponics
A place to discuss aquaponics

I used to have float switches, but decided they're too unreliable. In my large sump, I could only pump out 25% before the GB overflowed.
But after 5% evaporation, because the float switch was still set in the same posi, only 20% was pumped into the gb,
When I went away for work, the pump stopped pumping, because too much evap had occurred without me topping it up, even though there was PLENTY of water.

Moral of this story:
I use continuous flow with auto-siphons now. I can allow the sum to evap 80% before adding tap water, otherwise it tops up automagically when it rains. I rarely put water into my tanks. 80% in my system now is 2300L :-) Bigger is better, and indestructible is best. Not needing maintenance or drinking water is the ultimate.

I suppose what I'm trying to say is, if you don't like float switches (like me), then you have other options.
My next plan is to add a float valve to auto add tap water when the evap gets low enough to warrant it.

I have a small float valve installed to add tap water (we are on a well so no worry with treatment chemicals) if the system level gets really low. I am most likely to top up myself before getting that low by putting water into grow beds (letting it equalize a bit in temp, O2 and pH before getting to the tank) but the valve will cover if I'm away and things really drop.

I am still playing with the idea of having an extreme low water switch to cut the pump off if say there is a catastrophic leak somewhere that allows the pump to take water out faster than the float valve allows it in (very real possiblity.) This would save the pump from running dry and burning out. I just need to find a nice little relay so I can use one of the magnetic switches instead of a mercury switch not meant for potable water.

http://web4.automationdirect.com/adc/Sh ... -z-_Timers

Try these guys for relays and timers.

http://web4.automationdirect.com/adc/Sh ... ty_Sensors

And a capacitive prox sensor will read water level through the plastic wall of a tank or pipe. Makes a great level switch that is finely adjustible from the outside of the tank.

If you get a decent brand of proximity switch it will be almost bullet-proof for many,many years.
W euse them on some of our machines ,they are triggered on and off around 200,000 times a day , 6 days a week,52 weeks a year and many of these are stil lthe originals after 10 years at that usage. Omron seems to be one of the preferred brands.

Industrial Chappo, I've suggested it before, but everybody balks at the cost... I even wince, and I get them at cost price!

I had no idea of costs ,, but it would seem that a couple of them that where recently changed at my work and thrown in the garbage are actually ok

Capacitive proxes are the ones that will see water through plastic. Inductive proxes will see only metal. Two types you know.

you've forgotten about ultrasonic proxies

how about PEs? or Photo-electrics?

I was thinking of ways to replace the float switches with something more adjustable and reliable. It's hard to beat reading through the tank wall and they come with a LED that glows when it sees the water. Ultrasonic gap sensor work well enough as do the photo level sensors, but both need to be dunked into water to work.

And I won't ever use a mercury float switch, no matter what. Too dangerious if they break and no good way to dispose of a failed one.

Sorry, but re sonar, you are quite incorrect.

Much like rear parking sensors on cars, the sonar sensors measure the distance to the nearest object that will bounce sound back, through air.
I have a VERY nice one here that I'm playing with (at work) that will tell me the height of water in the tank between 0 and 6 metres (they make a 12 metre model too) to an accuracy of plus minus 1mm.

I'd love one at home, but not sure I could validate the expense. There are however kits (we used one at uni) that use ultrasonics for detection. perhaps they're worth looking into? They use a much smaller range, 1m being the max, and the resolution was about 10 - 50 increments I believe, but hey... it'd suit us...

You mean an ultrasonic level contoller like this one...Yeilds a 4-20 mA analog output for a PLC or whatever. Some have built in relays.
I use this one to measure flow rate through a flume and run the signal to a chart recorder. Very sensenative to minute changes in the height of the water behind the weir of the flume. Add a little math and you can calulate flow rate. Or control level.

I thought an ultrasonic level controller would be too expensive for a back yard system so I did not consider it.

Ultrasonic Gap sensors are more in the price range for a home system and act more like a float switch. One example: http://www.kthsales.com/website/vendors ... 10V40A.pdf


My guys did a nice job on the flume assemble, don't you think?

Yeah you're right, a gap-sensor is what I meant by a kit... 2x speakers with some circuitry, under $30 I would think - Some assembly required... but I do so love my level sensor, I'll try an get a photo for you as I'm onsite atm... they've got a screen on them for info, as well as 4-20 and HART protocol, and intrinsically safe. programmed via infrared remote.
$1k however is a touch out of my budget.

Actually now that I look at your link... umm not what I meant. you can buy level sensors such as the one you showed for your project, excepting that they're 'tuned' to a specific output, and operate a relay... I'll try to find an example kit,

Here's one set up just a car's reversing sensor... faster pings means closer object http://www.apogeekits.com/sonar.htm designed for personal use in the dark. but could be adapted to give decent output...

Here's one setup to the analogue pin of a PIC, giving a range of distances... perhaps you picaxe fanatics could find a use for this http://www.micro-examples.com/public/microex-navig/doc/090-ultrasonic-ranger

or a parallel port version for ppl using a PC to monitor their systems http://www.robotstore.com/download/3-740_Sonar_Exp_Instr_1.02.pdf

I may be wrong ,, but wheren't we talking about keeping a reasonable level of water in a tank of fish???????. Somehow we now have mooved to technology , and it's costs, for flying man to Mars. ( man as in mankind before I get trouble).