# Water sensor/power shutoff *urgent help needed*

#### kyroguy

Joined May 12, 2010
77
I am in urgent need of a sensor that will detect the presence of water and cut power to a power strip.

I have a small fish tank that has a rather elaborate filtration system. Twice recently small animals have made their way into the drain, plugging it. The tank quickly overflowed all over the floor. Fortunately I was home both times and noticed the problem immediately so I could manually cut power to the pumps. I am afraid that next time I won't be so lucky.

I have physically blocked the access to the drain opening but in the most recent incident it was an anemone that passed the block and plugged it. The body of an anemone is almost like jelly and thus it can pass through very small openings, especially when current is sucking at it. Therefore I can't make the block any stronger, there will always be a possibility that it can be plugged. So I have to come up with another way.

So long story short I need a sensor that I can mount to the lip/rim of the tank that will detect a higher than allowed water level and cut power to the power strip that all the tanks equipment is plugged into. Ideally it would be inline, in other words I could plug the sensor system into the wall and then plug the power strip into it. I am estimating the power draw of the system to be around 500 watts, so that is the amount that the sensor would have to be able to switch. Once the power is switched off it can remain off until I tell it to come back on manually. I will have to clear the block in the drain or fix whatever the problem is before restoring power to the system. If possible there could be multiple sensors that could be placed in various spots to detect a variety of leaks but this is not mandatory.

Hopefully I have described the situation clearly. If you know of a flexible commercial solution that would be great, but I think I am going to have to build something. Any suggestions on where to start would be much appreciated! Thanks in advance.

#### kyroguy

Joined May 12, 2010
77
The only problem with this solution is the float switch. I am working with a very small distance between "ideal water level" and "overflowing". I really need a system with probes that detect the water vs the float switch system.

I am going to take a closer look at this though. Maybe I can sub a solid state water sensor for the float switch?

Here is another interesting system I found. It is a bit more complicated than I was hoping for but it may work. I am reviewing it further as well.
http://www.aaroncake.net/circuits/pumpcon.asp

Thanks for the ideas so far.

#### erich_7719

Joined Oct 14, 2009
92
I have some IR sensors that could be used in the place of the Float Switch, but I am not at home to see who the Manufacturer was or where I got them from. When I get home I will look up that info if you would like.

#### kyroguy

Joined May 12, 2010
77
That would be great. I am only familiar with IR as in infrared. Is this what you mean? If so, how does IR sense water?

How would you reverse the circuit you suggested to turn off instead of on? Would it be a reversal of the float on the float switch? (I have float switches like this so I am used to working with them) Or does it have to do with the way the relay is wired? I suspect it is just hooking up to the relay backwards.

With a different sensor mechanism this is looking like it may be an ideal setup.

#### erich_7719

Joined Oct 14, 2009
92
You can look throught this site, http://www.gemssensors.com/content.aspx?id=282, for sensors "like" the ones I have. to get an Idea of how they work. (side note... The sensor I bought were much cheaper in price than the ones on this site)

As for How to set it up you would just put the mains on NO contact instead of the NC contact of the relay.

#### kyroguy

Joined May 12, 2010
77
I am following you so far. Any ideas on keeping the system "switched off" after a fault? I don't want the pump coming back on until I turn it on. Any creative way to plug it all in so it cuts power to itself and thus can't power the pump back on until unplugged and replugged?

I will take a look at the sensors you linked to. Thanks again.

#### erich_7719

Joined Oct 14, 2009
92
U1 is a SSR it is rated for my pump so we would have to size it up for your pump or if you like coil relays this could be modified for that too. S2 shows a float switch but a logic level IR sensor would work as well.

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#### erich_7719

Joined Oct 14, 2009
92
Stike the schematic in #8.

S2 would need to be high in the air low in the water.
S3 is still your reset switch

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#### kyroguy

Joined May 12, 2010
77
This is looking good. Now to ask some noob questions.

What is the thing just to the left of the 22uF capacitors with the little lightning bolt? Looks like a diode but I don't know what the bolt means.

Any special requirements of the 12v? In other words is there a minimum required ma? I have some old wall warts laying around, maybe I could salvage one?

I don't mind the SSR, would scaling it up be a problem or cost prohibitive?

All the little parts with numbers on them, just google the number to find the component? I have bought on ebay in the past with good luck, is there any problem with that strategy?

Lastly, once triggered will this stay off? If so how do I manually turn it back on?

Thanks so much for your help!

#### erich_7719

Joined Oct 14, 2009
92
If you mean the parts in the red box than the Blue box is just another diode, the green box has a LED with a 1K resistor.

SW3 would be something like a NO push button switch, so imagin if you will.
Water level is low, SW2 would be "Closed". Push SW3 would turn the and gate "on". D1 and D2 will hold the input near R7 high.
When the water level raises to high than SW2 would go low, hence causing the and gate to go low, untill the water level goes down and you press the push button down.

I don't know where you are located but I use Mouser for my electronics, so that I know exactly what I am getting.

If you can tell me what the watage is on your pump and if you mains are 120 or 220 that would help too.

Also I have the switches backwards the propper setup is below.

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#### kyroguy

Joined May 12, 2010
77
Excellent. I am in the US, Iowa, so mains are 120. The pump itself is less than 100 watts but I was thinking of plugging the entire power strip that all the components are plugged into (heater, auto top off, lights, other accessories) so the entire system would shut down. I would rather just have EVERYTHING off, even for several hours won't hurt it too bad. Any problem with plugging the entire system in? Figure 500 watts or so for everything. If it isn't a big deal I would build it even heavier for use down the road with bigger loads. If not, no big deal.

It was the component in the green box that I was questioning. I see now that it is an LED. My notification email read a different message than your post. It seemed to suggest that everything in the red box could be removed to simplify the circuit. Is this correct? What would be the advantage of keeping it included. Simplification would be the obvious benefit if it could be excluded. Even if it only told me the thing was working I suppose I would want to keep it!

I will check out mouser. Thanks for staying up late to help!

#### erich_7719

Joined Oct 14, 2009
92
OK Clarification, I goofed and than edited the post. The diode in blue can and rilly should be removed. The LED could be removed but the resistor has to stay so that the resistor and the 22uF Cap can act to de-bounce the switches.

I can see about the relay for every thing, just so you know thats a lot of power going through it.

Also this is the link to the sensors I am using. http://shopsensors.madisonco.com/item/all-categories/optical-switches-compact-economical/opt4303-3?&plpver=10&origin=keyword&by=prod&filter=0

Give me a while for the relay, though.

#### erich_7719

Joined Oct 14, 2009
92
This relay would be better http://www.mouser.com/ProductDetail/Omron-Electronics/G3NE-210T-US-DC12/?qs=sGAEpiMZZMtHD6BhCPGf2pzm/lBpqtlmpy6JzcisRCA=, it is rated for 10A. 500W at 120V is about 4.1A. The relays you were looking at only goes up to 2A.

You will need a heat sink if you have every thing on the circuit. So might I sugest putting every thing except the heater on the circuit since the heater probably draw the most current, followed by your pump or maybe your lighting.

A wall wart of about 500mA should do, I did not calculate that and it is very likely to be high. Also it would be better to regulate the wall wart since they are next to never regulated.

#### kyroguy

Joined May 12, 2010
77
How do you regulate a wall wart?

#### erich_7719

Joined Oct 14, 2009
92
Page 22, Figure 7, of the Data sheet attached, would due nicely, to regulate the wall wart.

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