# DIY smart auto top-off



## Jay1st (Jan 16, 2006)

Hi , I am new to this forum and for my first thread I would like to introduce you to my "less stupid than others" DIY auto top-off.









Now I am able to set a minimum level (float switch#2) and a maximum level (float switch#1).

Basically it works like this:

Water in the tank evaporates,float switch#1 goes high (1 in logic state or in the lowest position if you look at it) and nothing happens.
The water is still going down and THEN float switch#2 goes high and starts the pump to fill up the tank.
When float switch#2 goes low (0 in logic state or in the highest position if you look at it), due to the pump filling up the tank, nothing happends.
The high level is reached and float switch#1 goes low and THEN the pump STOPS.

This simple system avoids the use of a timer to keep the pump from running during very short times.

The setup can be made by soldering directly the wires, comming from the float switches, the pump, and the 12V supply, on a DIL16 IC support on wich you connect a DIL 16 micro relay.
Be sure to have some Normally Closed float switches when the float thingy is LOW !

Here is a pic of mine :









Cheers, JAy.


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## rrguymon (Jul 22, 2005)

Well If I am looking at your diagram correctly you have set your self up for a flood if the relay fails. It appears the relay powers the pump when it is off (no power to coil state). I think it would be much safer if the relay had to be energized (power the to coil) to power the pump. IME when relays fail (almost 100 %) the normally closed contacts stay closed.

It also looks like if the bottom switch (not sure if that is 1 or 2 from your discussion) was fail open or solder joint broke the system would just chatter (on off on off on off on off) if the top switch was closed.


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## Jay1st (Jan 16, 2006)

The relay is shown in de-energized state and the pump runs ONLY if FS1 and FS 2 are on.

I have it on my tank for a while and no problems (except snails in the float switch)..


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## wiste (Feb 10, 2006)

Curious about the cost of your setup. 
Can you give a cost breakdown and specific parts used?


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## rrguymon (Jul 22, 2005)

Ok. Must a Euro thing. It just looks odd to my American mind. Both float switches are shown closed applying power to the relay coil. The relay is also drawn in an energized position (for amercican schematics).

If the float switches are drawn low water position and the relay is drawn de-energized (opposite of what it should be if the switches are closed) then It should work ok.

Rick.


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## Jay1st (Jan 16, 2006)

The cost is very low. Less than 25$.
I guess if I give you the parts ref for the supplyers we have in europe it might not help much, so I'll give the general list of parts:

_2 float switches like those in the picture (7 euros here), N.C. when the floating thingy is in the lowest position. 
_1 12V DPDT micro relay DIL 16 (like THIS
one)
_1 DIL 16 IC support (easy relay change)
_1 small 12V pump (I use a pump for a camping-car water system, 8 liters/min)
_a buch of wires and some heat shrink tubing.


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## Jay1st (Jan 16, 2006)

> Both float switches are shown closed


No, look carefully at the picture, they are open position.


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## rrguymon (Jul 22, 2005)

Jay1st said:


> No, look carefully at the picture, they are open position.


Ok I see there is every so slighty a gap. They sure looked closed to me. Looks like a good system should work fine and a simple electrical failure will not flood your house.

Rick


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## Jay1st (Jan 16, 2006)

> They sure looked closed to me


Sorry for that, next time I'll choose an other type of switch in the software I use to make it more visible, tx for the remark that may induce mistakes.


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