3 DIY projects for under $3

Looking to build some simple but useful devices without breaking the bank? Here are three DIY engineering projects for under $3.

Motion-activated burglar alarm

If you’re not one to lay out the cash for an expensive alarm system but would like a sense of security, this project is for you. The best part is that it’ll cost you no more than $2.

As you’ll see in the video below by Kipkay, you can purchase impact alarms at your local dollar store. Meant to stick to your windows, if these devices detect broken glass, a high-pitched siren will go off. To make your very own alarm system, here’s how to get started. 

Remove the three screws in the back of the alarm, then pry the case open with a small screwdriver. Inside you’ll find a circuit board, a sensor, and a speaker.

The next thing to do is to replace the on/off switch with a small tilt switch, which activates whenever the switch is tilted. Typically this switch costs about 50 cents online. After the new switch is installed, it’s time to put everything back together. Because the switch is activated when it’s tilted, be sure to use a small magnet to hold it in the off position.

One good use for such an alarm system is to attach it to the back of your personal items, such as your laptop or bicycle. As soon as somebody moves it, the alarm will blare off. That’ll teach whoever’s messing with your belongings to cut it out.

Remote-controlled camera

With this fun project, you can control your camera from afar. All you have to do is equip your digital camera with a remote shutter. It's a lot simpler than it sounds and costs less than $3.

Video by Matthew Panzarino.

First, you’ll need an infrared transmitter. This will trigger your smartphone to use your DSLR camera with the help of a downloadable app called DSLR box, which will send the appropriate signals to your camera once you plug the transmitter into the headphone jack.

To get things rolling, you’ll need an audio cable, some solder, LEDs, wire cutters, and a soldering iron. To begin, clip down your audio cable and carefully remove the outer casing. Next, strip off the positive wire, which should be red, and then the negative, which should be black. Leave the ground wire separate. If your cable has two ground wires, make sure you twist those together.

From there, solder the LED positive side to the black, and then the negative side to the red. Attach your LEDs, making sure they’re positioned opposite of one another.

After this simple setup, it’s best to wrap electrical tape around your LEDs to keep them separate, and it’s also wise to wrap some tape around the whole thing. Then you’re ready to send those signals to fire the camera.

Noise-isolating earbuds

If you often find yourself in a noisy environment, be it in your home or office, and would prefer some silence for the sake of concentration, you must give this project a try. Like many of us, it's likely you’d prefer not to spend hundreds of dollars on premium earbuds, but would like to hear more clearly out of the ones you already have. The good news is that for less than $1, you can make your own fully-functional noise-isolating earbuds.

First, you’ll need a pair of earbuds. Fortunately, most kinds will do, such as Apple’s earpods, which include plastic removable earbuds (these should be the kind that come straight out of the box with your smartphone). You’ll also need typical earplugs, which you might have sitting in your garage (if not, check out your local hardware store), a pair of scissors, and something to poke a hole in the earbuds. You’ll see a biopsy tool being put to use for this purpose in the video by Nicholas Spooner, but a mechanical pencil can also do the trick.

Once you’ve got your supplies ready, squish your plastic earbuds down so that they’re flat, and then with your scissors, cut them to the size you’d like them to be so that they fit comfortably in your ear canal. Next, let your plastic earbuds settle until they shape themselves back to their normal size, then squish them down until they resemble circles. From there, you’ll poke a hole into the plastic earbuds with your tool of choice. When your plastic earbuds are back to their original sizes, stretch them over the actual pair of functioning earbuds, and you’ll be set to journey into your own world, noise-free.

Though it’s a simple hack, the holes in the plastic earbuds allow the sound to come in through the earbud and not the surrounding environment. It’s a simple solution to an ear-splitting problem.

Have your own tips or tricks? Sound off in the comments below.