Improving Range for SimpliSafe Motion Detectors

If you need to secure a room or building that isn't part of your main house, or you live at Scrooge McDuck's mansion, you'll find that the range of SimpliSafe is most likely unreliable or nonfunctional as you head away from the base station. I have a home office that's located in my barn, and it was out of range of my SimpliSafe base station - until now.

There have been a couple of other Instructables posts detailing how to extend the antennae of entry switches. This is the same methodology, but applied to the newer SimpliSafe motion detector units. Hats off to HillbillyLifestyle, as I'm merely building off of his article.

It goes without saying that these modifications are frowned upon by SimpliSafe and will void your warranty, I'm not responsible if you break it in the process, you do this at your own risk and expense, don't run with scissors, blah blah blah.

You'll need at least the following:

• About a foot (30 cm) of thin-gauge wire
• A hobby knife or razor blade
• A soldering iron
• Solder for electrical connections
• The ability to solder or at least muddle your way through it
• Wire strippers
• "spudger" tool or something to gently pry plastic pieces with
• A medium to small size Philips head screwdriver
• A flat blade screwdriver of moderate size may help

Like many modern devices, the plastic housing of a SimpliSafe motion sensor is held together by little tabs that snap together.

Use your spudger tool or a prying tool that is preferably plastic to pry apart the front and rear pieces of the sensor.

Tabs are as follow

• 2 beefy tabs on the top (button)
• 1 wimpy and fragile tab for each side
• 2 moderately strong tabs on the bottom

The way I proceeded was:

• Take out the battery to expose the two lower tabs
• Gently work the tabs loose on the bottom through the battery compartment, and stick something in the resulting gap so that it doesn't close on you. I used an old credit card
• Slide your spudger or similar prying tool along the sides to undo the single clip per side. These break easily, and as you can see from my photo, I broke both of mine. These tabs aren't vital and mine still went back together without an issue.
• Lastly, with just enough unreasonable force and while still being gentle, separate the upper tabs. I ended up rotating a flat blade screwdriver in the gap above the side tabs because these top ones are stubborn.

To perform the modification, you'll need to access the underside of the circuit board that faces the back of the sensor.

1. Remove the single Phillips head screw in the center of the board.

Take care not to touch the infrared sensor.

2. Pull the board off of the four plastic posts and gently fold it backward over toward the battery compartment.

3. Carefully remove the microswitch at the top of the housing by sliding it out. You can gently use the yellow wires to help move it.

4. Set aside the plastic button piece that sits atop the switch so that you won't accidentally lose it.

As per the photo above, locate the printed labeling, "ANT_1" on the printed circuit board. (PCB) This is where the antenna trace starts. It ends toward the upper left of the board. We're going to extend this PCB trace with a piece of wire.

With a hobby knife or razor blade, gently scrape off a small section of the green coating at the end of the antenna trace. You want to expose the bare metal underneath, which is what you'll be soldering to.

If you haven't already plugged in your soldering iron, you're going to need it hot for the next step.

Using a drill bit slightly larger than the diameter of your length of wire, drill a hole in the housing for the antenna to exit through.

Referring to the first photo, you can see that I drilled mine in the bottom of the housing to the lower right of the battery holder. You could theoretically drill it in a lot of different locations, so do what you think will be most practical or cosmetically pleasing.

SimpliSafe uses a frequency of 433.92 MHz.

To calculate its wavelength, we divide the speed of light, 299,792,458 m/sec by our frequency in Hz.

This is therefore 299,792,458 / 433,920,000, which is 691 mm

In our quaint unit of measure, this is around 27.2 or 27 3/16 inches.

From my very, very limited knowledge of antenna theory, a half-wave antenna is apparently more reliable than a full-wave antenna. (If you're a subject matter expert, feel free to disagree and comment. I'm doing my best here.)

Therefore for a half-wave antenna, you're ideally looking at a length of around 346mm, or 13.62 quaint inches.

I measured approximately 1.75 inches (45mm) as the length of the PCB antenna trace.

13.5 - 1.75 = 11.75 inches. (346 - 45 = 301 mm)

Therefore trim your wire length to 11.75 inches or around 30 cm.

Strip a small portion of the wire insulation away on one end of it, and solder it to the bare metal you exposed at the end of the antenna trace.

Route this wire through the hole you drilled, taking care to avoid pinch points.

• Put the PCB back on its four posts
• Put the microswitch back into the slot in the housing, taking care to properly position the little plastic button.
• Make sure the battery wires are back in their original positions
• Put the screw back into the center of the PCB. (I forgot to do this the first time)
• Place the two halves of the housing back together. The top clips require what feels like unreasonable force and make an alarmingly loud snap.
• Place the battery back in the battery holder.

Mount your sensor and test it out.