Gadgetory

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 kind of 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 flood 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 you're gonna 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 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 removed from the negative 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've 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 MOSFET so what we'll do now is create that connection take the resistor and connect one end of it to the gate terminal of the MOSFET connect the other end of that 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 MOSFET 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 inside except for those two lead wires which should be sticking out the side 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 we'll set off an alarm so at this point you might be thinking that's a lot of work to save just ten bucks the problem with other $15 off-the-shelf sensors though is if you want to cover a whole house you've really got to 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