Wearable object detector with tactile distance feedback

It’s not very often that, in the bustle of life, I (and maybe most like me) think about the senses we take for granted. Now and then I happen to notice, or actually think about the fact that some people live without some of them.

I’m really hoping I won’t say anything stupid here, because I don’t really know what I’m talking about, or how people might think about it, so I ask for forgiveness if I do.

I think it can be hard to deal without seeing, probably the most important sense to understand the environment around us.

I suppose at home one can have a very controlled environment; know where (almost) everything is, but I think it’s much harder to deal with unknown places.

There are already some tools to help, like the cane, the clicker and maybe others I don’t even know.

Having watched the “Sue Thomas: F.B.Eye” TV series, and being an electronics engineer, I had all sort of ideas of devices that could be helpful to deaf people, but most were cumbersome, unpractical, or beyond my abilities. Anyway, it got me thinking about ways to improve any sense disability, including blindness.

When I first learned about the VL53L1x distance sensor, I immediately thought that this is something that could be useful: it’s a distance sensor, with a relatively narrow beam, not affected by sounds (and not using ultrasounds that might affect the guide dogs). Unfortunately, it doesn’t work well outdoors because it uses light so a bright day would make it useless, but I think there are enough indoors situations where one might find it useful: to find a doorway, to avoid obstacles that are not on the ground (the cane does that), to find something on a table, etc.

So, I thought it’s worth a try.

I designed a device that can be worn on the wrist, so it can be easily pointed to the direction of interest. In fact, the device is fast enough that, by moving/rotating the wrist, it can easily “scan” the environment, such that the user can immediately know which way objects are, and how far, within the scanned area.

The feedback is given through a tactile transducer worn on the outside of a finger, such that the palm/hand can still be used, even as it may reduce scanning ability, as one wouldn’t want to rotate the wrist while holding a cup of coffee.

After proposing the idea, the Contest Masters gave me some invaluable feedback. Distance feedback is more important than just knowing something is “there”. I went beyond the proposed change in intensity or volume of pulse or sound, which can be hard to gauge in noisy environments, to use Pulse Width/Frequency Modulation of a finger mounted haptic/tactile transducer that can be felt and easily interpreted regardless of ambient noise, and without overburdening the hearing, which I think is very important when one can’t see.

Another proposal was to have the device in the palm, to better guide the hand to pick up whatever object might be the “subject”, but I feel the palm should be free, if it’s to do the actual picking up. However, the idea opens up the possibility to wear in on the “inside” side of the wrist, with the same benefit, so, depending on the situation, one could rotate it inside/outside (like a watch) as needed. Thank you Masters!

The boldest Contest Master’s proposal was to have the device identify and describe the object using AI or such technology. That would be the bee’s knees, but is way beyond the scope of this project which is meant to be fast, small, instantly-on, independent of any cloud or other serious processing power. It seems there are services that can transmit video from a phone worn in front, that can describe the surroundings, but while very useful, they are something else and may not be ideal to easily locate a cup on a table, for example.

The prototype I made is rather ugly, using sections of a glove to hold the device and transducer on the hand, but is fully functional.

It was built inside an AA battery holder so it could be made much smaller and rechargeable. Also, I used a laptop speaker for the tactile transducer which works very well, but smaller devices could be found/designed to further reduce the size of the system.

The transducer could in fact be mounted on the surface of the device that touches the skin, if worn in a sensitive location. This way there would be no wire, just the device. The prototype was made so I could experiment in multiple places.

The videos below show the device used to detect a small object (mug) on a surface, and to detect distance to a curtain. Since I can’t “show” tactile feeling, I put the tactile transducer near the camera microphone and the clicks you hear are “actuations” or movements of the membrane that would be felt on the skin when mounted. Alternate clicks show push/release, so they are easy to feel and interpret. You’ll have to turn the volume up to hear them, since they are just movements, really, not Beeps.

Detecting a small object:

Detecting Distance:

When nothing is within range, there are still pulses, to reassure the user that the device is on. When an object is detected nearer than the (configurable) maximum distance, the pulses become more “urgent” (faster, closer together) so that after a period of trials the user can easily tell how far the object is. The current range is just under 2 meters, I think it could be extended to 4m.

One easy way to “calibrate” one’s sense is to touch a wall, feel the fast pulses, then move back and forth; in time the distance gauging should become second nature.

On to the build.

I used an Arduino pro micro (it was the smallest I had; any, really, should work) to run the code, read the distance from a VL53L1x breakout board, run some algorithm to transform the distance into practical pulse timing, and send distance-modulated pulses to the transducer.

In the picture above, the Arduino was lifted for clarity.

The schematic is in the schematics section and the code is in the code section; select the type of Arduino that you have, before building/uploading.

If the project is of interest, future (but hard) improvements might include some detection of object size, and feedback by changing modulations between Pulse Position, Pulse Width, and Frequency modulations to convey the extra information to the user.