Short range Proximity Sensor?

After working with the SmartThings Motion Sensor, I can see a use for a very short range proximity sensor to create a touchless switch. I am quadriparetic, so handsfree is always good for me.

I have multiple devices in my house that work with a hand wave. They all use proximity sensors at a range of two to four inches. These include a wall switch, faucet, soap dispenser, and a trash can where the lid opens when you wave your hand over the sensor. None of these are networked. The soap dispenser costs less than $20, so I’m assuming the proximity sensor itself isn’t that expensive. They’re all very short range–if you wave your hand at them from a foot away, they don’t trigger. But of course a networking component would add cost.

Does anyone know of any networkable sensors of this type that could be added to a SmartThings setup? I’d really like to be able to use a touchless switch in one room and trigger multiple actions throughout the house.

It may turn out that “non-passive” detection will work better than a PIR motion detector.

When washing hands, the user’s hands are placed under the nozzle and before the sensor. The activated sensor will further activate a pump that dispenses a premeasured amount of soap from the nozzle.[6]

Radar-based sensor[edit]
This kind of sensor sends out bursts of microwave or ultrasound energy and waits for the energy to reflect back. In a stagnant situation, the energy will bounce back in a normal pattern. When hands are placed in the basin, the energy emitted from the sensor will bounce back irregularly which triggers the dispensation of soap.[7]

Photo sensor[edit]
This mechanism is composed of two parts, a source of focused light (usually a laser beam) and a light sensor. When the user’s hands are placed in line of the beam of light, the pump mechanism is activated by the disruption that is sensed by the light sensor.[7]

Passive infrared sensor[edit]
Infrared sensors detect infrared energy that is emitted by one’s body heat. When hands are placed in the proximity of the sensor, the infrared energy quickly fluctuates. This fluctuation triggers the pump to activate and dispense the designated amount of soap.[7]

Great question. I’m not aware of any products with that short of a range. You might be able to play with placement. Pointing a sensor towards the ceiling or placing it behind another object may work for you.

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Thanks! I have another forum topic on the range of the SmartThings motion detector where I describe doing just as you suggest here. I took a small insulated Bento box without a lid and put it on a bookshelf. Then I put the motion sensor inside the box. The motion sensor was lying flat pointing up. This now functions as a touchless switch. Someone just walking by does not trigger it. But if you wave your hand over the top of the box it does.

That’s actually exactly what got me thinking about the need for a short range proximity sensor. It took several trials to get the motion sensor set up just right to avoid being triggered by nearby activity.

Because I am in a wheelchair, I am very limited in the height range where a touchless switch is usable. Someone who can stand could probably just face a motion detector towards the ceiling and put it on a high shelf. Or try mounting it facing down towards the floor, put it down very low, and make it a foot switch.

But because I need to keep it in a range from the armrest on my chair to about 2 feet above that, it’s also unfortunately in a range where there’s likely to be a lot of activity.

The bookshelf plus Bento box worked for this particular case, but I would really like a short range proximity sensor for some other cases I have around the house.

I know the sensors exist, they’re already in use in many small household appliances as well as hospitals and office buildings. I just don’t know if any exist that are networkable.

A friend of mine who does robotics says many people build arduino touchless switches using the Sharp proximity sensor GP2Y0D805Z0F, which detects in a range of 0.5 to 5 centimeters.

He lives in England and is not familiar with SmartThings, but he said if the ST Shield works with an Arduino Uno to receive data, it should be possible to build a networked touchless switch, although he didn’t know what size it would end up being.

Have you thought about foregoing touchless and perhaps working with some kind of NFC implementation?

There are plenty of ways you can interact with NFC tags, maybe even with some kind of wearable.

The Sharp business looks… sharp… but I haven’t done any sort of ST / Arduino programming to guess how difficult it would be to implement, plus the Shield component that would link everything together seems to be out of stock without any sort of ETA.

NFC could definitely work IF it’s handsfree. (I’m quadriparetic, think Stephen Hawkings. It’s difficult for me to grasp, pull, or pick things up. I don’t have a mobile phone for this reason. I use an iPad that is mounted on my wheelchair. Decent voice control and most things work with one knuckle.)

I would be ok with wearing a wristband type thing. (I’m waiting for the right smart watch–maybe 2016 at the rate things are advancing.)

But is there an NFC “reader” that works with SmartThings now?

Ok so let’s put that on the shelf then…

How about a cheap Android tablet with Tasker, AutoVoice and SharpTools?

You can use that to voice-control individual items in ST as well as fire up phrases, and it works today at minimal cost.

I don’t have any android devices now so don’t know anything about the ecosystem. I was intrigued by the Gear S watch, which is Tizen, not Android, but it’s not standalone and I’m not ready to get the mobile phone as well just for the limited functionality the watch currently offers.

For me, handsfree needs to be really truly handsfree, not just voice recognition after you use your hands to open the app. Or for that matter take your phone out of your pocket.

I’ve looked at the Ubi, but for my purposes I’d need 4 or 5 in the house in different places and the cost/benefit isn’t there for me.

I have an Amazon Echo on order, and as I said I’m hoping the fall 2015 smart watches, whatever they are, will include something that will work for me. At some point some of this stuff will converge in a consumer-ready fashion.

Meanwhile, I’ll look into the android options currently available for more information. Thanks for the suggestion!

You can look into ibeacons too, since you’re already on iOS, but I don’t know anything about the interface of some third-party software with the beacons then back over to ST.

I know you could get Estimote beacons (a set of 3 is $99) and place them strategically around the house, and use a Tasker plug-in to detect when you’re in range, which would then trigger an action (which I assume could be a “Thing” in SharpTools).

I haven’t tried this, but the theory seems solid. :smile:

ibeacons definitely have potential, although weirdly Apple didn’t include iBeacon mentions in HomeKit. Maybe they’re waiting for the watch?

Anyway, right now I don’t know of any iOS iBeacon management app, including emote, that can talk to SmartThings. So that throws things back over to Android. But then the tablet gets more expensive, too, right? Because you need BLE to do the presence recognition.

I agree, though, what Apple calls “immediate” range for an iBeacon should work for a near range proximity sensor and again a wristband wearable would work for me. But I think we’re still in the “coming soon” category.

Does the Gear S recognize iBeacons? I’ll have to check.

I don’t know… I have an original Gear, a Gear Fit and now a Moto 360, but I’ve never really paid too much attention to what they support – they’re more of an extension of my phone.

If your wheelchair is electric why not just have wired Ubi into it’s power? Ubi runs off a standard USB power supply. Not need for multiple units and always available.

It’s a good question, but not really practical. No one I personally know runs anything off of a wheelchair battery–we’re desperately trying to conserve power as it is. If a wheelchair battery runs completely out of power, it won’t usually recharge. If it dies while you’re out, you may have a hard time getting home again. You’re lucky if your battery lasts two years as it is–most last only one.

Bigger batteries both make the chair heavier and increase the risk of fire. So wheelchairs are usually outfitted with the smallest practical battery.

Every couple of years someone comes out with a $300 device to allow a phone or laptop to run off the power wheelchair battery, but these companies mostly seem to stop selling them in a year or two so I’m assuming people just don’t find them practical.

My ipad is on a mount attached to the chair, but runs on its regular battery and gets recharged at night with a regular charger, at the same time the wheelchair is being recharged.

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Bluetooth based beacon sensors seem like the most likely approach to enter the ecosystem “soon” (this was to be a major feature of WigWag, but, well, they have other problems even getting the basic product into production.

There are lots of great ideas here, and some are great “hacker” projects:
To toss up one idea:

I’m guessing that perhaps your wheelchair makes a particular “whine” sound?, though hopefully not very loud? A circuit that can detect a particular frequency range in a room is actually rather simple and if paired with a cheap Ardunio and Wifi (such as a Spark Core), could easily integrate with SmartThings. Overall, not a trivial project, but definitely a feasible one that might have a market beyond your immediate wishlist.

…CP / Terry.


A sound associated with my wheelchair might work if I wanted a “crossing the geofence” sensor. But what I want is a touchless switch that I can turn on when I want to, and only when I want to. That’s why I’m talking about very short range proximity sensors–in the neighbourhood of 2 to 4 inches. So it won’t turn itself on most of the time.

For example, my zwave doorlock has a motorized deadbolt. That’s important because I can’t easily work the turnbolt on the inside of the door to let someone in. But I don’t want the door to unlock itself everytime I drive by!

I can work it fine from the SmartThings app, but that’s not handsfree.

Instead, I’ve set up a SmartThings Motion Detector as a touchless switch. So now when I want to unbolt the door, and only when I want to unbolt it, I go over to the switch, wave a hand over it, and the door unlocks. Excellent.

So these use cases are for proximity sensors, not presence sensors. Very short range proximity sensors.

Apple’s iBeacons use “ranges,” including a range called “immediate” which is in the 2 to 4" range. If you’re shopping in a store, for example, you’d only get the immediate response if you actually held your phone up to the iBeacon. That’s different than the “near” range, when you’d get it if you were just walking by.


Thanks for clarifying again…

  • “Very short range” could be done with an NFC tag bracelet (bare bones old cell phones with wifi and nfc readers could be a reasonably affordable and SmartThings connectable hack to read these) – but maybe overkill.

  • A strong magnet would work just as well if you can carry one and wave it near enough to any magnetometer based sensor (also present in most smart phones, though a SmartSense Multi uses a magnetic sensor as well).

  • A light sensor might work, if you carry a small laser or flashlight or reflector.

All of the above options require you to carry or wear something, though…
My instinct is that using one of the sensors that works “well” for automatic soap dispenser (earlier post), is likely the most practical – but let us know what you mean by “very short range”.

…CP / Terry.

Can’t carry anything smaller than a burrito. Can’t eat with a spoon, either. I can make a sort of hook with my hands, which is how I control the joystick on my powerchair. But I can’t tighten my grasp. That’s fairly typical of quads.

That’s why “handsfree” means really handsfree in my particular situation.

If I’m wearing something in a wristband style, I’m going to be wearing it all day. That’s OK, I’m hoping eventually for a smart watch that works for me. But not something I have to slip on and off as needed to trigger a particular device.

Currrently I use very short range proximity sensors on a number of devices in my home, as I mentioned. I expect the technology differs somewhat, these were all storebought devices. A typical range is 2 to 4 inches. It may be that some are motion sensors and some are infrared and some are a trip beam, but they all work well.

The soap dispenser is a cheap one made by Emerson with a red light that’s visible at all times. I suspect it’s a trip beam of some kind.

The trash can is an expensive one made by Simple Human that has a lot of cleverness built in. The initial trigger range is very short, about 3" right over the sensor. But once the lid opens the trigger range extends to about 15" so the lid doesn’t close again while you’re still putting stuff in. No idea what that technology is, but it’s not a trip beam, it requires motion over a horizontal distance.

The Sharp proximity sensor my friend mentioned uses two infrared beams that it triangulates to estimate distance, but it’s set to no more than 5 centimeters, so it’s mostly used to keep things from running into walls and for touchless light switches in hospitals and labs.

Apple iBeacons define the “immediate” range based on signal strength, but it means really really close. Used in stores to allow a shopper to interact with a specific product or for ticket dispensers. Obviously you don’t want your ticket to print while you’re 12 feet away in the queue. Apple has four ranges altogether, I think, and you set different actions for the different ranges.

So two to four inches seems practical to me for a touchless switch.

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Most of these devices (except if they have obvious extra intelligence like the Simple Human trashcan that adapts distance when the lid opens…) use fairly easy to find components. Some of these could actually be wired directly to any number of cheap Z-Wave devices which have open/close terminal blocks exposed internally (Monoprice sells a few choices), or to a wifi arduino compatible if actual programming logic is required to configure and read the sensor (Spark Core or cheaper).

So: The optimistic hacker approach is to figure out the technical details of the sensor setups in the things you have that “work very well”. One of these might be the path to a good solution or off-the-shelf recommendation. Make a list?

My limited understanding from what my friend who recommended the Sharp proximity sensor GP2Y0D805Z0F told me is that the issue is that all the various sensors are analog, and you need something to convert that to digital. Which apparently a lot of people have done with arduino. But then, of course, you need the ST hub to recognize the digital indication. (The Sharp retails for about $6, so it’s one of the least expensive high quality components.)

So the Sharp would say “Something is near” (which it does as a signal strength).

The device to which the Sharp was wired would convert that to a digital “On” indicator AND communicate that to the ST hub.

The ST hub would then take action based on the “On” through something like the Things Start to Happen SmartApp.

I don’t know how that matches up with the devices you mentioned, though. Would they do analog to digital conversion?