See how to build your own flood sensor out of inexpensive parts

[MUSIC] I've taken a look at quite a few flood sensors over the last couple of months and basically, all of them work using the same logic. You've got two or three probes that are coming out of the sensor and when those probes touch water, the circuit is completed and the electricity that flows through the water, sets off an alarm in the sensor. The thing is, after talking with one of our tech wizards, Steve, I was struck by how simple the basic mechanic to make one of these things would be. So we got some supplies from online and from some local hardware stores, and we put together a plug sensor that will set you back for under five bucks. Here's how we did it. First things first, you're gonna have to get your supplies. That means Means you're going to pick up a door/window sensor, some electrical tape. Some copper wire, a mosfet and a resistor. Then there are the tools that you need. We wanted ours to look really nice and professional, so we wanted it to actually live in the body of the original door/window sensor. Sensor. In order to do that we had to use a soldering iron. But really this circuit could really easily be set up using some alligator clips like these. So the first thing you can see Steve doing here is opening up the actual case of the door window sensor. Now it's really important here that you get a door window sensor that has a simple on/off switch. If you get one that has more options or an LED light built in, then you'll run into some problems with the circuitry. The second step will be disconnecting the wire that is currently connected to the negative battery terminal. Then you'll connect that wire that you just remove from the negative terminal Terminal to the drain terminal on the MOSFET. Next, you'll take a new wire and connect that to the source terminal on the MOSFET. Then you'll connect the opposite end of that wire to the negative battery terminal. Basically at this point we have broken the circuit using the MOSFET. And the only way that, that circuit can be completed is if we activate the gate terminal, that's that middle terminal on the mosfat. So what we'll do now is create that connection. Take the resistor and take one end of it to the gate terminal of the mosfat. Connect the other end of that resistor to the negative battery terminal. Now take a new wire and attach one end of it To the positive terminal of the battery. Now take another new wire, and connect it between the resistor, and the negative battery terminal. Then you'll want to wrap each of those mosfat terminals, those three side by side terminals, in electrical tape. That way, they won't contact each other, and set off a false alarm. At this point, you'll want to make a hole in the side of the door window sensor case. Finally, you'll want to arrange all the components in such a way that you can close the case again with all of them in sight. Except for those two lead wires, which should be sticking out the sides through the hole that you created. Now if you've done it right, those two lead wires, if they are touched together, or if they're joined by a body of water, will set off an alarm. So at this point you might be thinking, that's a lot of work to save just ten bucks, but the problem with other $15 off the shelf sensors though, is if you wanna cover a whole house, you've really gotta buy quite a few sensors. And even if they're $15 a pop, that cost really adds up. But with this sensor that we just created for under five bucks You can add just a little bit of extra copper wiring and turn it into a device that will cover a whole room. So what we've got here is our makeshift flood sensor and we have two copper wires that run parallel out of the body of this thing. All you have to do is use adhesive strips like the ones that we've used here to make sure that the wires run parallel to each other never making contact, so no false alarm is ever sent. Then, if water pools anywhere along this track It'll set off an alarm. So for a couple of bucks, a little extra copper wire, and a little bit of gumption, you've got yourself a device that not only replaces a $15 flood sensor, but could actually secure whole rooms against water damage. [SOUND]