Sensible Watch

Leverages touch-based interaction on the watch strap for accessibility instead of small buttons, catering to the differently-abled.

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The sensible watch uses a customized watch strap consisting of capacitive and resistive touch sensing, to interact with the watch UI.

Watches have buttons on the side, which can be challenging to operate for individuals with an amputated arm. These controls require fine motor skills or grip strength that may not be possible with a prosthetic limb or missing limb.
Modern watches offer various functions beyond telling time, timers, alarms, and fitness tracking features. Navigating through these functions, adjusting settings, or activating specific modes may be challenging without the use of the non-dominant arm.

For Individuals with an arm amputation, they can wear the Sensible Watch on their functional arm or their amputated arm. The touch-sensitive strap can detect touch gestures and movements, enabling users to interact with the watch using their amputated arm, functional hand or different parts of their body (eg Chin,Elbow etc). The strap works with prosthetics.

By simply tapping, swiping, or sliding the strap across parts of your body, you can navigate through different watch functions and menus.

When the watch is worn, users can access different functions such as time, stopwatch, alarm, etc by swiping. But they cannot change the time, alarm, etc.

When the watch is removed from the wrist, users can change the time, alarm, countdown, etc by performing touch gestures on the strap.

The plan is to use a hybrid resistive and capacitive touch system, both technologies are combined to offer improved performance and functionality. Here's how it should work:

  1. Touch detection: Capacitive touch sensing is primarily used for touch detection. It provides faster response times and can accurately detect multiple touch points simultaneously, allowing for advanced gestures like pinch-to-zoom or multi-finger interactions.
  2. Pressure sensing: Resistive touch sensing is employed to measure pressure. It can detect the level of force applied to the touch surface. By combining pressure sensing with capacitive touch detection, the system can differentiate between light touches and firmer presses, enabling more nuanced interactions.
  3. Compatibility: Hybrid systems often retain the compatibility of traditional resistive touch technology, which can be operated with a finger, elbows, or prosthetics. Capacitive touch technology, on the other hand, generally requires a conductive object like a finger for touch input.

By combining the strengths of both technologies, hybrid resistive and capacitive touch systems aim to provide a more accurate, responsive, and versatile touch experience for prosthetics as well as epidermal gestures.

To prevent accidental presses different strategies can be used, similar to palm rejection, double tap, or lock screen which are currently used in smartphones.

Why not turn the watch face into a touch-sensitive display as opposed to the strap?

The primary reason is visual obstruction, functionalities such as changing time, setting the alarm etc need visual feedback to be accurately set. Touchscreen based Smartwatches mitigate this by having buttons or using the connected smartphone to change the time, set alarm etc.

What about the Apple Watch assistive gestures for single-hand usage?

Although they do work well, it requires dexterous movement of fingers, and also the user interaction is more suited for smartwatch applications such as play/pause music. It is quite cumbersome to change time, set alarms, countdowns, etc with the hand gestures such as pinch and clench.

Won't a capacitive sensing strap be affected by the hand it is worn on?

Yes, to some degree but we will be measuring the changes in capacitance over a specific region as opposed to an absolute value. 

But won't you need to use two hands to wear the watch?

The watch strap utilizes magnets for attachment and offers a convenient way for users to wear the watch using only one hand. 

How will capacitive touch be implemented?

Many microcontrollers come with capacitive sensing pins (eg ESP32), which can be connected to flexible copper pads inside a flexible PCB.  

Designing a custom flex sensor - The Bela Knowledge Base[Image of Trill flex sensor from:]

During the prototyping stage copper tape will be used and later a customized PCB will be designed.

How will resistive touch be implemented?

Pressure-sensitive conductive sheet (Velostat) will be sandwiched between two flexible PCBs with exposed traces. 

Topology and dimension of 9 sensing elements in the 3×3 matrix.[Image From:]

During the prototyping stage copper tape along with velostat will be used and later a customized PCB will be designed.

The circuitry will be embedded in a silicone strap, which is made by pouring liquid silicone into a 3D-printed mold. Another way would be to use a flexible 3d printing filament to make the strap.

  • 1 × Seedstudio XIAO ESP32 S3
  • 1 × 0.96 inch OLED
  • 1 × Velostat
  • 1 × LiPo Battery 500mAh
  • 1 × Resistors 1K

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  • Prototype V1 Demo

    Josh Joy06/15/2023 at 09:08 0 comments

    The V1 prototype uses capacitive touch sensing to access watch menus by swiping on the touch-sensitive strap using the elbow, wrist, and body rubs.

  • Down Sizing

    Josh Joy05/29/2023 at 19:41 0 comments

    The seedstudio Xiao Esp32 S3 development board was selected for the next version due to its extremely compact footprint and also the fact that it has integrated battery management circuitry. The XIAO ESP32 S3 board has lesser capacitive touch pins available, the next iteration's focus will use microcontrollers with a greater number of capacitive sensing pins.

  • Getting Started

    Josh Joy05/29/2023 at 19:39 0 comments

    For the first version, the ESP32 was used due to the fact that it has capacitive sensing GPIO pins. The initial versions focus on capacitive touch-based sensing and later versions will incorporate resistive touch.

View all 3 project logs

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leo hartman wrote 06/25/2023 at 20:18 point

great idea!  Thanks for sharing

It cd also be combined with motion sensing and with other mobile devices

...real-time physics in and control signals out

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Josh Joy wrote 06/29/2023 at 05:39 point

Thanks Leo, do you mean using the watch to control other devices such as a smartphone?

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Josh Joy wrote 06/10/2023 at 08:44 point

Thanks Poorna :)

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poorna.chanddra wrote 06/10/2023 at 07:50 point

Interesting project Josh. I'm sure it will be of great help to the ones with special needs.

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