Turning off pump with high level water probes

[Chrisbes]

I am very new to electronics (but hopefully learning fast) and am looking for a way of turning off a pump (via the water bridging a simple pair of probes at the top of the tank) in a timed flood and drain hydroponics irrigation set up, where the tank is dry between pumping periods.

The required repeat timer I have found (courtesy of Ron) at **broken link removed** but the override turn off I cannot work out. Could anyone help me please?

 

[Boncuk]

Hi Chrisbes,

you don't want to have the pump run dry if there is no water and you want the pump to switch off it the reservoir is filled to the top.

That's at least what I'm reading from your problem.

To achieve both it doesn't require electronics.

For pump deactivation under no water conditions use a pressure switch fitted into laundry washers to regulate the water height. They can normally be preset to three different pressure values - select the lowest.

To switch off the pump if the reservoir is full I recommend using a floating switch, normally produced with an adjustable cord length on the floater.

So the logic wiring of the two switches should be

reservoir not full, water supply present: pump on
reservoir full, water supply present: pump off
reservoir not full, water supply absent: pump off

in other words both switches must be "AND"ed to achieve the desired switching.

Boncuk

 

[crutschow]

Sump pumps often use a single bi-stable toggle switch connected to a float with a sliding rod and adjustable stops on the rod. When the float rises to where the high water stop hits the switch, it turns the pump switch on. When the float reaches the low water stop it turns the switch off. Simple but effective.

 

[Chrisbes]

Hi Boncuk and Carl,

Thanks for the replies. I didn't make it clear in my question, but the reason for wanting to use probes is that there is no room for a float switch as the tank is filled with a growing medium, in this case clay pebbles known as 'leca' and plants.

Chrisbes

 

[Boncuk]

In that case I suggest using electronic "sensors" probes.

To make them durable I recommend not using DC for water level detection, as DC has the negative side effect of extra wear (besides corrosion) due to the electrolytic process involved when just measuring resistance between probes.

If you like I'll design a circuit for you using low voltage AC (+/-6V). The output circuit might then be connected to a relay which you can use in conjunction with the pressure switch.

Boncuk

 

[Chrisbes]

Hi Boncuk,

Thanks a lot, that sounds like exactly what I need. If you could help me with a circuit that would be great!

Chrisbes

 

[KMoffett]

Maybe this one? **broken link removed**

It's #250 on this site...Circuit lab, diagrams,Free circuits, Electronics periodical, e-mags: India

Ken

 

[blueroomelectronics]

Those EFY schematics and designs take me back to 1976.

Also makes me think of "No Soup for You" guess it's the name.

Interesting designs that could kill you are always fun for the casual hobbiest.
**broken link removed**
Why not use a battery supply, I mean how many IR remotes do you test a day? Also there should be a 4.7uF cap on pin2 of the TSOP1738

 

[rWAVE]

Alternate Plan to Using Probes

Chrisbes,

I have been building hobby hydro systems for many years (am currently working on another "flood-and-drain" system, also using expanded clay pellets - Hydroton). I once considered using probes (and other more exotic approaches) for level sense, but abandoned them all as they all had inherent problems.

Now I use a very low-tech solution which works VERY well. My nutrient feed line is flexible tubing, running from the pump (submerged in the nutrient tank), which is inside much larger diameter (I like 1") PVC pipe. The PVC pipe is used as an overflow drain, set at the desired height (below the media top so algae doesn't grow) within the growing chamber. This allows you to pump nutrient with no fear of overflow (you actually want overflow into the PVC pipe, not overflow in you growing chamber), while the returning nutrient (via PVC pipe) falls back into the nutrient tank and thereby aerating it. Nutrient tank aeration is one of the key reasons to do it this way! Obviously, when the pump is turned off, your growing chamber will drain back through the pump, with no aeration. In addition to nutrient aeration, the vacuum created by each draining cycle of the growing chamber pulls fresh air into the root zone; one of the reasons why flood-and-drain is a great system and why plants grow SO fast! Enjoy.

Richard

 

[rjvh]

you're growing tomatos or not

Robert-Jan