Introduction: Empty Water Detector

Picture of Empty Water Detector
This project is an 'empty water detector' to tell you when the water is gone from a vessel - originally, I designed it for a christmas tree, but it will work for your dog's water bowl or just about anything else.

Parts list

  • 220k Resistor
  • Small Perfboard
  • 2N3906 Transistor
  • 2x or 3x AA Battery holder
  • 3mm Red LED
  • Extra wire for the probes

You can order the kit from Gadget Gangster & grab a PDF version of these instructions, here. You can also share your own projects on Gadget Gangster, too.

Here's a video demonstration

Step 1: Gather Materials

Picture of Gather Materials

First, gather all your materials. If you've ordered the kit from Gadget Gangster, your project will come with a halfboard - put the halfboard in your vice, as shown in the picture. You'll also need a soldering iron and 2 AA batteries.

Step 2: Add the Resistor

Picture of Add the Resistor

Add the resistor from M3 to N7.
Bend out the leads on the other side of the board, flip the board over and solder the resistor down, and trim off the excess wire.

Step 3: Add the Transistor

Picture of Add the Transistor

Flip the board back and add the transistor from O6, O7, and M8. The flat side of the transistor should point to the edge of the board.
Spread apart the leads, flip the board over, solder & trim the excess wire, and flip back over.

Step 4: Add the LED

Picture of Add the LED

Add the LED from P6 to Q6. The longer lead goes into P6, shorter lead into Q6. Spread apart the leads, flip the board over, solder the LED down and trim the excess.

Step 5: Add the Probes

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The probes are the wires you'll put in the water;

Take the red wire, cut in half, and strip the ends of each wire, & tin the ends (lightly twist the ends of the wire together, heat with your soldering iron, and add a bit of solder.
Once the wires are tinned, put on wire in P7, the other wire in Q8. These wires are the probes that you'll put into the water. You can tie the other ends of the wire in a knot, with one end a little shorter than the other.

Step 6: Connect the Batteries

Picture of Connect the Batteries

Lastly, connect the battery pack. Thread the black and red wires through a few of the bigger holes on the bottom of the board for stress relief, and connect the red wire to Q23, Black wire to M22.
That's it! Add 2xAA batteries and insert the leads into the water you'd like to test. When the water's gone, the light will illuminate and you'll know it's time to add water!

Comments

kathrynelliott63 (author)2017-05-23

*I have no electronics background*

The link to your site doesn't work for anymore (for me at least). For a novice I wondered if you could make the schematic available? also how would you add a buzzer into this too?

Thanks,

yhankru (author)2014-02-18

Can you give a schematic diagram?

matthewu (author)2012-08-16

Great simple project, much better than sap!!! :-)

triumphman (author)2011-12-27

water does not trigger the system ? I put an alka-selzter tablet between the wires, that are squeezed by a spring clip, when water reaches the alka-seltzer tablet it crumbles and the wires touch, thereby completing the circuit. The fish upstairs, starts to sing and dance, and I rush down to the basement and turn off the main water valve and repair any leaks! Simple ! It works, tested it with water and the tablet. Asparin would also work. I like simple. Less work and parts to go bad!

triumphman (author)2011-03-18

I need to make this in reverse. I want to detect water if it leaks from my ancient basement boiler. My home has a concrete below ground basement. It has no drains or sump pumps. So if my boiler blows or a pipe leaks I will have a very ugly swimming pool! And all my workshop will be under water. So if I could nip any leaks in the bud, I would be much happier! Any simple DC plans would be deeply (no pun intended) appreciated! I have a catfish wall plaque that talksand moves. It has a 6V.DC battery box (4 AA @ 1.5 VDC each) power and 6VDC wall transformer too. I would like to run two small wires down to the basement and the plaque upstairs where I can hear it! All I need is a way to activate the catfish with a moisture sensor. Any wizards out there have a simple way to do this? I can do basic soldering and schematic stuff! But simple is better. Thanks.

musick_08 (author)triumphman2011-05-13

I hope this helps. But if you use the plaque idea you'd have to take it apart and (im assuming it has a button to activate it) put 2 wires where the water would be (not touching though) and solder the 2 wires to the leads of the button.

triumphman (author)2011-03-18

I need to make this in reverse. I want to detect water if it leaks from my ancient basement boiler. My home has a concrete below ground basement. It has no drains or sump pumps. So if my boiler blows or a pipe leaks I will have a very ugly swimming pool! And all my workshop will be under water. So if I could nip any leaks in the bud, I would be much happier! Any simple DC plans would be deeply (no pun intended) appreciated! I have a catfish wall plaque that talksand moves. It has a 6V.DC battery box (4 AA @ 1.5 VDC each) power and 6VDC wall transformer too. I would like to run two small wires down to the basement and the plaque upstairs where I can hear it! All I need is a way to activate the catfish with a moisture sensor. Any wizards out there have a simple way to do this? I can do basic soldering and schematic stuff! But simple is better. Thanks.

R1Ch0 (author)2009-05-17

Question... Will this work with petrol / gasoline? I know it's a noobish question, but it's better to be safe than blown up. Thanks.

skylane (author)R1Ch02010-09-23

DON'T even think about that.
That's why they use floats in gas tanks.
It would be much simpler and probably cheaper but extremely dangerous.

chainsawjames (author)R1Ch02009-05-19

Do it and let us know how it works out. A deep cycle battery would be great for that.

AndyGadget (author)R1Ch02009-05-18

'Fraid not. Impure water (such as what's sitting in your Chrissy tree pot) has a low enough resistance to trigger the LED. Petrol has a much higher resistance and wouldn't. And of course, you shouldn't put ANYTHING which might generate sparks (such as a battery pack) near your petrol.

cowtipper97 (author)2009-07-03

ooh this is cool! im gonna use it for the water bowl in my snake's cage. can you draw up some schematics so i make pcb instead of using a prefboard?

CODIY (author)2009-05-13

Nice Instructable. I made a water level sensor on a similar premise. I was wondering if you might include a schematic of the circuit? I can figure it out from the instructions, but for people who might not have the same type of perf board and little knowledge of electronic components, it would be a little difficult to know which leads to connect where without the grid designations.

Gadget Gangster (author)CODIY2009-05-14

No problem - It's a really simple circuit. I added a png and sch version to the project page (on the bottom left).

CODIY (author)Gadget Gangster2009-05-15

Excellent. I think that including schematics is a great way to help people learn about electronics. While your instructions are very concise, they don't really help someone learn how to read a schematic and understand how that translates into the physical project. Thanks much for including the schematic on your project page! (as I said, your instructions are great, but step 4 might have the LED being put in backwards)

Gadget Gangster (author)CODIY2009-05-15

It LOOKS like the LED is going in backwards, but my LED's actually have a longer cathode lead (quite odd, actually).

hoo-t (author)2009-01-30

I have a gravity fed watering system for small animals. I uses a 5 gallon plastic bucket which is elevated roughly 6 feet off the ground. I've been searching for a way to alert me when the buckets are close to empty to prevent the animals from running out of water. I knew I had found it when I found this instructable! Absolutely perfect! I made one of these, substituting a flashing led, and placing the whole thing in (of all things) an Altoids tin! Added a NC momentary switch to the probe to test the batteries, and it works beautifully! A red flashing light lets me know when I need to add water! Thank you!

Gadget Gangster (author)hoo-t2009-02-01

Cool! Glad you found it useful. The one I build for this instructable has been sitting on my coffee table for about 2 months - I think the batteries will last pretty much forever.

Gadget Gangster (author)2009-01-05

I think water just needs a bare minimum of electrolytes to conduct flow. Tap water works just fine. Bottled water did, too. I don't have any distilled water to test, though. One weird thing, I tested it for a few weeks with a glass of tap water, and after 2 weeks or so, a little bit of white flakes were on the bottom of the glass. Do you think that the electrical flow is causing the minerals to precipitate? Our water is super hard.

imakethings (author)2009-01-04

you could add salt

Padlock (author)2009-01-03

This won't work with distilled water, though...