Modify $15 SimpliSafe Entry Sensor As a Wired Switch





Introduction: Modify $15 SimpliSafe Entry Sensor As a Wired Switch

The SimpliSafe (SS) security system consists of a wireless hub controller and a number of battery-powered wireless sensors, all communicating over a Z-wave network. One sensor in particular is very inexpensive, the $15 "Entry Sensor" wireless magnetic switch. The sensor consists of the sensor module and an external magnet, which triggers a normally-closed magnetic reed switch inside the sensor module. You stick the sensor on a door or window frame, and the magnet on the door or window itself, and as long as the distance between them is an inch or so or less the switch remains closed.

Alas, there is no provision for attaching a wired dry-contact switch. Having this module include wired switch contacts would be a boon to SS customers. You could implement a wireless doorbell, attach existing magnetic, motion and smoke detectors to the SS system, and create multiple-position sensors (to permit a closed and half-open window, but not a full-open one, for example).

Modifying the SS Entry Sensor turns out to be pretty easy. The first one took me a while, to best determine wire routing outside the sensor module, so I've documented the process in this instructable.

Step 1: Step 1: Open the Sensor Module and Remove the Circuit Board

This takes a knack the first time you do it. There are two covers on the back of the module. The first one simply slides off, and covers the battery compartment. It also has a 3M adhesive strip fastened to it. Remove this cover and take out the battery if installed.

Next you have to remove the inner cover. You do this by prying at the three latch indentations with a flat blade screwdriver. This took me a few tries before I figures out this technique: use a large flat-blade screwdriver and pry it in toward the center of the module. Each corner should pop out in turn. You then have to fiddle with it a little to get it out the rest of the way.

Before you can remove the circuit board you have to pull out the battery contacts. Start with the contact on the long wire, at the end of the module. Use a needle-nose pliers and wiggle the contact back and forth to work it out. It's just a friction fit. As soon as this contact is out, the circuit board will become free at one end.

Use the same technique on the mid-case battery contact. Once it is out, you can gently pull out the circuit board. My board had holes for screws, but no screws were installed, so it was entirely friction-fitted. Some might have screws, however, so check for those and remove them if necessary.

The bare board appears in the picture above. The thin glass tube is the magnetic reed switch, and the metal hoop on the bottom of the board is the Z-wave antenna. Take care not to bend the LED leads, as the LED must line up with its exterior opening during reassembly.

Set the board aside for a minute and proceed to the next step, modifying the case to provide a wiring path.

Step 2: Step 2. Cut Two Notches for Wiring Path

You need to make two notches through which you'll route the wires outside the module case. The first notch goes in the inner cover, marked in red in the photo above. Simply clip out a small notch with a diagonal cutter and pull out the plastic with needle-nose pliers.

Make a similar notch in the module outer case right at the end of the module serial number, also marked in red in the photo above. Take care not to obliterate the serial number label.

Head on to Step 3.

Step 3: Step 3: Prepare Wires for Soldering to Magnetic Reed Switch

I used a single twisted pair from an ordinary solid-core Cat-5 Ethernet cable (commonly called "riser cable"). You could use stranded wire as well, although attaching is a bit trickier. Solid copper wire stays where you put it, making assembly easy.

Start by measuring a length of twisted pair (I recommend at least a foot) and then cutting the two strands in an offset as shown in the first picture above. Then strip the wire and loop each piece around a lead wire on opposite sides of the magnetic switch. You'll solder these in the next step, so a strong mechanical connection isn't needed. Route the wires along the board toward the right-hand end (with the battery cutout on the left).

IMPORTANT NOTE (9/16/2016) ! Several people have emailed me indicating that they have cut the leads to the magnetic reed switch, or what they thought was the reed switch. You don't need to do this, and I suspect you might cause problems. One person misidentified the antenna hoop (the large-gauge silver wire U on the same side of the board as the LED) as the magnetic read switch and soldered their external relay to that. Needless to say, that won't work either. The reed switch is the glass tube on the top side of the board with all the other parts. DO NOT REMOVE IT.

Proceed to Step 4, soldering.

Step 4: Step 4: Solder the Connetions and Re-install the Board

This is a very basic soldering task. The magnetic switch is not very heat sensitive, so no heat sink is necessary. Just apply the minimum amount of solder necessary for a good mechanical connection. Take care not to melt the rubber pads on the board, which seem to provide cushioning.

You're now ready to reinstall the board. This is the reverse of the dis-assembly process: install the mid-case battery connector, seat the board, and finally install the end-case battery connector.

Seating the board requires one trick: lining up the LED with it's opening in the plastic housing. I've done a number of these mods now, and the easiest way for me is to have a light behind the module so that it shines through the LED hole, then line up the LED so that it starts into the hole before you get the board fully seated.

Note that if you do the board re-seating before installing the mid-case battery connector, you'll have to start over. The wire on the mid-case connector is too short to install it once the board is fully seated.

Step 5 is to test the module before you get it all reassembled.

Step 5: Step 5: Test the Module Before Final Assembly

Test by reinserting the battery and waiting a minute for the module to sync with the SS hub. The LED flashes a couple of times once this happens. Then test the module with the magnet, just to make sure the magnetic switch still works. The SS hub should emit a chime when you open the switch by removing the magnet. Now repeat that test using the wires: short them together, then separate them. The chime should sound.

If either test fails, investigate. I has one instance where the wire I was attaching had a break under the insulation. It's a lot easier to fix that now than after everything is reassembled.

Step 6: Step 6: Replace the Module Covers With Wires Routed Outside

Replacing the covers is straightforward. First insert the inner cover, sliding the side with two latches under their tabs first by angling the board in, then pressing the board down on the third latch. Make sure the wire is routed through the notch you cut earlier.

Then route the wire through the second notch and replace the battery cover by sliding it on. The module is now ready to use. It might be a good idea to run one more test before you put it into operation.

Attach the wires any kind of dry contact switch, such as a traditional normally-open doorbell button. When
the button is pushed and released, the SS chime will sound. Never connect the module to any kind of wires that already have power on them, as the module itself is already supplying power to the magnetic reed switch. Any external power is likely to destroy the SS sensor electronics.



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33 Discussions

Man am I glad I found this site. I’ve found similar instructions for the abode system and have tried doing the same on the new ring alarm sensors. I’ve been able to get one of my doors soldered to the wireless sensors. The hardwired door sensors is one of those recessed version that push in to close and a cylinder comes out when opened. Anyways, I have not been able to get any of my other sensors to work. I’ve soldered them the exact same way but they won’t work. I solder spare wire to the reed switch and then used an IDC connector to reconnect the newly soldered wire to the old wire going directly to the sensor. Any help would be so GREATLY appreciated!


Can this technique be used to modify a motion sensor? I have an ADT alarm system from 2011, and I'd like to convert to SS.

1 more answer

I don’t think so. The magnetic sensor has an actual on/off reed relay to tap into, since that relay is what the magnet operates. This modification exploits that relay to permit integration of wired sensors. I don’t know if the motion sensor has an exploitable relay, but it technically wouldn’t need one, since it need only generate a particular IP packet to signal a motion alarm to the base station.

But by the same token, you may not need to modify your ATD motion sensor at all, assuming it’s one of the wired types that opens a relay to signify an alarm. Simply wire that sensor into series with a SimplySafe magnetic door sensor, and you convert the ADT sensor to SS.

Do the external switches need to be the normally open or normally closed type?

1 reply

Normally closed. In fact, most alarm sensor switches, even in traditional systems, are wired normally closed, because this lets the system detect tampering with the wiring. Any "opening" of the circuit from a cut wire will trigger an alarm.

Some good ideas here. One comment, though.

You said modifying it would allow securing windows in multiple positions. This can be done without modifying anything, by simply buying additional magnets from the SimpliSafe web site. Place the sensor on the frame, and two magnets on the sash, or vice-versa, and the alarm will show closed in either position.

Great instructions. Wanted to add that I was able to do this with sensors bought this week without removing the circuit board and battery connectors. I used a soldering iron to poke a whole through the plastic sensor and ran the wires through there and to the side of the battery. I cut the wires staggered so there was no excess and looped and soldered them. So far so good on 4 wireless units monitoring 13 windows and a pair of French Doors. I used wireless sensors on the three main doors and 4 critical windows however I might go back and swap these to the pre-wired and use the extra sensors to monitor the upstairs. I wish Simplisafe would either build this in or offer a multi sensor with a 4 zone block on it.


I have ordered all these parts. I am making a perimeter alarm at my storage lot. Which alarm out put would I connect the wires to so the entry sensor will trigger? Worried about the voltage coming off the receiver into the sensor. Thanks


OK. So I have the SS2 and I took an unused entry sensor, I snipped the leads to the reed switch and soldered on two wire leads. Now the sensor doesn't work at all. If I touch the two leads together then hold them apart, nothing happens. If I ground the lead on the fat end of the board to the metal bar over where the reed switch was, it registers with the base station as an entry sensor. Has SS changed something in their sensors to defeat this hack?

2 replies

I don't why felt need to cut the legs. That might have something to do with it. Not sure. But I wonder if you accidentally cut Antenna, instead of reed switch.

I just installed mine with wires on reed switch and works fine.

Can someone please confirm if this still works with the latest (July 2016) version of the SS entry sensor? (That is basically the factor that will determine of I go with SS or move to something else) .. Thank you

Can someone please confirm if this still works with the latest (July 2016) version of the SS entry sensor? (That is basically the factor that will determine of I go with SS or move to something else) .. Thank you

1 reply

it works

I purchased it from amazon and tried it last night.

Worked just fine with my wired sensors


2 years ago

Let me know if you figure out how to add a relay to the standard SimpliSafe SIren so that I can set off something that I can actaully hear! Thanks!

What about using an existing hard wired siren? Does the base station have an output that could drive a relay? How?

I have both FireX wired smoke alarms (independent of the alarm panel) and a fire/smoke detector hard wired into my existing alarm. Can one or both be used with the SimpliSafe? If using a door/window module interfaced with the hard wired detectors can the system be programmed to report an alarm as fire vs. break in?

Hi, Was wondering if you take this switch that you hardwired and connect to the siren, would that set off the simplysafe. I have a wired Brinks system fully operational this way you can use the wired system with the wireless. Do you think that might work ?

1 reply

I don't see how txt would work. SimpliSafe doesn't send a signal out to the awitch, it only receives switch state.

Nice job on this. Has anyone looked at how to trigger an existing hard wired siren to the SimpliSafe system?

Thank you for figuring this hack out. Like many others I have a hard-wired house and I'd like to use some of the original senors. I guess my next step will be to figure out the jumble of wires in the pictures and see what happens.

I guess I'll unplug the power & common and and test the lines to see if the contacts complete the circuit. This hack should allow me to use them, right?

Any advice would be appreciated.


Old Wires.jpg
1 reply

So, my layout as you can see near the bottom of the picture above:


Zone 5

Zone 4

Zone 3

Zone 2


Zone 1

I have continuity between Zone 1 and Com when the magnetic switches are closed and a break when I open a switch. My SimpliSafe sensor is rewired to work and touching the leads sends a signal to the base (in test mode) that the sensor is open. But, no matter which way I wire it to the Zone 1 and Com wires I cannot get the magnetic switch to trigger the SimpliSafe sensor.

Very frustrating. Should I plug the old alarm into the wall outlet? There's a resistor inline between the Com and the Com wires (there's two wires for the Com & Zone 1 to the mag switch). I've tried going around it and that doesn't help either.

Can someone give me some idea of what to try next?