Designed as an alternative to the traditional cane, this wearable device lets a user intuitively “feel” the distance to obstacles in his or her environment.
A semi-finalist in this year’s Hackaday Prize, Maker Neil Movva has developed a non-contact, long-range alternative to the traditional cane. As its name implies, Pathfinder is a sonar glove that enables a visually-impaired wearer to navigate around obstacles by quickly scanning the surrounding environment.
Pathfinder works by measuring the distances of objects in close proximity and then translating the data into gentle pulses that are felt at the wearer’s fingertip. The closer something is, the faster the taps; conversely, the further away, the steadier and slower the tap. With practice, the glove lets a user point and get a sense as to how far away an object actually is, up to 500 centimeters.
With an ATmega328P as its brain, the gadget is comprised of an inexpensive ultrasonic sensor, a transmitter and receiver operating on 60kHz sound waves, a haptic driver, an accelerometer/gyroscope combo chip, a vibration motor, and a LiPo battery.
“Of course, we have a very popular AVR running the show. The TQFP package is remarkably easy to work with at the home lab level, and of course the chips themselves take a lot of abuse when prototyping. I’ve deployed dozens of these across the various prototypes Pathfinder has been through, and it isn’t leaving anytime soon. (Low power, simple layout, easy SW dev),” Movva writes. “When we get closer to production, however, I’ll consider moving to an ARM chip (SAM series, maybe?) that might offer more HW amenities at the price of increased complexity.”
The ultrasonic sensor, which is interfaced with the ATmega328P and mounted at the head of the device, sends out an inaudible signal. These are transmitted towards the target and are reflected back to the sensor. By multiplying the time it takes to complete a roundtrip by the speed of sound, and dividing that by two, the Pathfinder can calculate the distance to a nearby thing. This data is then processed by the embedded MCU, which pulses a small pinky motor through a pair of transistors for haptic feedback. Aside from that, an accelerometer provides contextual awareness, allowing the wearable to sleep when inactive or when the glove is facing the floor. In its original prototype form, the LiPo battery pack offers 20 hours of continuous operation.
“In the end, the glove came together well enough to be tested under typical use conditions. I found that there was a significant learning curve in using the glove for precise, fine motor tasks, but basic large obstacle detection was easy enough for untrained, fully blind users,” the Maker adds. “On my own, I was able to perform more scientific trials, and so I designed a repeatable gauntlet of tests that I or other sighted users could perform while blindfolded to demonstrate typical use of the device.”
These experiments consisted of picking up a glass of water on the table, locating a person in an open area without initial orientation and navigating around an open area with randomly placed obstacles. Fortunately, Movva was able to pass all three tests after getting used to the device.
Looking ahead, the Maker intends on improving the Pathfinder’s design with a shrunken-down board, swapping out an 8-bit AVR for a 32-bit ARM chip, reducing power consumption, incorporating gesture recognition and supporting Qi wireless charging. The goal was to provide the blind with a new way to navigate their environment, one in which does not require physical interaction and can be used at long ranges. Mission accomplished, Movva! You can explore the Maker’s project in more detail on his Hackaday.io page here.