How to Use Smarthome Door Sensors Around Metal

Open/close sensors, like those included with the Samsung SmartThings kit, are great for automating certain actions whenever doors or windows are opened. But if you’re having trouble getting them to work well, it might be because the metal on the door or window is causing issues with the magnet system that’s used on the sensors. Here’s how you can get around that.

The workaround is quite simple, although it doesn’t look the prettiest and doesn’t quite blend in. But it at least works. The sensor basically needs to be at least a few inches away from the nearest piece of metal to prevent interference.

First, try to mount the sensor normally to see if it works first. Even if a door does include some metal, it still may work just fine. It’s mostly doors that are heavily made out of metal (like garage doors) where you’ll usually come across problems. If you do, though, this trick should help.

The image above shows what the final product looks like—a door sensor mounted to the top of my garage door that’s a few inches away from the nearest piece of magnetic metal. Setting this up is pretty simple, but requires a bit of creativity.

What You’ll Need

To do this, you’ll need a couple of tools and materials, including:

The aluminum flashing (shown above) will come in an L-shape when you buy it, but it’s pliable enough that you can bend it all into a flat piece using light taps with a hammer. It’s one of the reasons we’re using aluminum for this: it’s very soft and can bend easily to your will, allowing for the most customizability. It’s also non-magnetic, so it won’t interfere with the sensor.

Step One: Mount the Sensor

We’ll start by mounting the larger sensor portion off to the side by a few inches from the door (or above). In this guide, I’m doing this with my…

How Does the “8x” Zoom on My Point-and-Shoot Compare to My DSLR?

Your camera may boast “8x zoom”, but most DSLRs do not advertise values like these. So how do they compare? The answer is more complex than you may think.

That “8x” value that doesn’t necessarily mean objects in the photo will look 8 times bigger than they do with your eyes. It just means things will be 8 times bigger than its most zoomed-out position—but two cameras in their most zoomed-out positions will not look the same size.

Every lens affects your image in a different way. A wide angle lens warps the perspective in the image so it shows more than you could see with your naked eye. A telephoto lens does the opposite, zooming in like a telescope to distant objects. These things are separate from the actual “zoom” function on your camera, so one 8x zoom lens may not make objects as large as another 8x zoom lens.

So how do we calculate how much bigger an object appears in a photo compared to your eyes, where you’re currently standing? To find that out, you need to know the focal length and field of view of the lens you’re using.

“Canon vs Nikon:”
Did you know about this one camera setting that ruins your pictures? Go to

Focal Length and Field of View

In photography, the focal length of a lens is the distance between a the camera’s sensor and the internal components of the lens itself. This focal length determines how close objects look to your camera and what part of the scene actually fits within the picture—otherwise known as your field of view. A massive, telescope-like lens with a 1000mm focal length will make objects look very close. Lenses with smaller focal lengths will make objects appear farther away.

Many lenses can “zoom” to different focal lengths. For example, an 18-135mm lens will let you zoom from an 18mm focal length to a 135mm focal length.

Here’s an example. I shot the following two images with my Canon 650D and an 18-135mm lens.

The first photo was taken at the shortest focal length: 18mm. It’s a pretty wide field of view.

The next photo was taken in the exact same place half a second later. The only difference is that I’ve zoomed in to use the lens’ longest focal length, 135mm.

As you can see, the field of view is a lot narrower in the second photo than the first, because we’ve zoomed in on the mountains.

Here’s the catch, though. Different lenses, at their shortest focal length, will show things differently. Remember that 1000mm telescope lens? Even if you don’t zoom in with it, you’re still seeing things much closer than a camera with an 18-135mm lens. So focal length alone isn’t…

Act Quick, Get The Arduino and Raspberry Pi ‘Board Basics’ Deal

Whether you’re controlling your home’s temperature with your smartphone or helping your refrigerator keep track of its contents, the interconnected world is our world. Getting up to date and then staying current is the trick.

A new ebook bundle from Make: and Humble Bundle pulls together the best, most informative titles we’ve produced on Raspberry Pi, Arduino, and other sensors, pairing them with Lego, Mindstorm, and robots.

We’re calling it the “Board Basics” bundle and it runs Wednesday–Wednesday, Feb. 22–March 7, featuring our best-selling titles from the “Getting Started With” series of tutorials as well as plenty of project-based books that result in such great creations as space rovers and bots.

With a combined value of $360+, this bundle can be broken up into groups or you can buy the whole thing. Whichever you choose, you choose your price point. As always, Make: and Humble Bundle combos benefit the Maker Ed nonprofit organization.

Easy to gift (just click the link!), the Board Basics bundle is not only perfect for intermediate makers like yourself but for the emerging techies in your household. As a nice bonus, everyone who buys a bundle at the average price or above gets the chance to enjoy discounted subscriptions to Make: magazine.

“Really understanding the new microcontrollers, mini computers, and sensors now on the market is essential to firming up basic maker skills,” Make: books publisher Roger Stewart said. “These are bedrock texts for that knowledge as well as great project tutorials. And you can’t really beat the great deal on Make: magazine print and digital subscriptions.”

Here’s the Board Basics rundown:

Pay $1-$7 or more receive:

  • Make: magazine, volume 38: Everything you need to know about DIY consumer electronics.
  • Make: Basic…

Check Out This Phone’s Molecular Sensor Scans and Analyzes Objects

Changhong, a Chinese consumer electronics company, has released a new cell phone that can analyze the molecular properties of food, liquids, medicines, and more, CNET reports. The device is capable of reading body fat percentage, the quality of produce, and more.

Called the H2, the phone is fitted with a tiny, near-infrared spectrometer. Hold it over an object for a few moments, and the H2 will shine a light that penetrates its surface. The object’s molecules then bounce the light back to the phone, and the changed light is collected and analyzed in a database cloud.

The H2 is the first smartphone to harness this technology, which was developed by Israeli tech startup Consumer…