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I’m (Not) Falling For This


The Ambularm – an ambulation alarm

At St. Vincent Hospital, word spread quickly about the quirky new hybrid doctor/engineer down in the basement, and one of the senior physicians soon wondered if I could help him solve a big problem: patient falls. Despite instructions not to do so, patients would get out of bed and fall down on the way to the bathroom. Even the best hospitals experienced hundreds of these events per year, causing everything from bruises to hip fractures to head injuries and deaths. Bedside rails didn’t reliably prevent this, and restraining the patient in bed wasn’t acceptable either.

Weight sensors in the bed had been tried, but they didn’t activate until the patient had left the bed, and they didn’t protect a patient who was sitting in a wheelchair either. So we hit on the idea of a battery-powered tilt sensor that would be worn in the thigh, and would sound an alarm as soon as the femur (thigh bone) angled downward more than 30 degrees.

I built a crude prototype with Radio Shack parts in a plastic box with an elastic strap to hold it on the thigh. It looked promising so we had a PCB and molded case professionally designed, and eventually received a patent. The Ambularm made a distinctive bell-like sound that brought a nurse running before the patient got to his/her feet, and fall rates were cut in half. I wasn’t involved in the later stages, but apparently the Ambularm stayed  on the market until 2015.

Badges of Honor


A Wireless, Wearable Assist for Assisted Living

In 2015 I connected with Bill Reed and Lydia Lundberg, innovative pioneers in the assisted living industry. At their company, Elite Care, Bill had been searching for technology solutions that could satisfy the conflicting demands of safety vs. autonomy for their residents, but found no suitable commercial products. The staff and residents were already wearing identification badges, so Bill hoped we might develop these into Bluetooth wireless “smart” badges that could enhance residents’ safety and comfort, as well as staff efficiency. 

Besides being nametags, the badges functioned as emergency call buttons. We experimented with auditory feedback from the call button when pressed — a short audio recording of a loved one reassuring them that help was on the way — but this didn’t prove helpful. More successful was the inclusion of accelerometer, gyro, and temperature sensors to measure activity and environment. And finally, the badges could serve as locators. With Bluetooth receiving stations (“hubs”) installed throughout the facility, a central server could estimate the location of each badge based on signal strength at each hub. The badges could also act as receivers to detect which other badges were nearby, potentially providing data on social interactions and staff presence with a resident. 

Early prototype PCB

Early prototype case

Final prototype PCB

Final prototype case

Filling a KNeed


Wireless, Wearable Tracker for Post-Op Knee Rehabilitation

Over a million joint replacement surgeries are performed annually in the U.S., a number that’s expected to explode as my fellow boomers injure or wear out their knees and hips. While the surgery and joint implants have been continually refined, the rehabilitation phase at home hasn’t benefited from technology — yet. Orthini, a Portland startup, was formed to address this need. I came on board as a consultant to create a proof-of-concept prototype. Think of it a specialized version of a fitness tracker that measures knee range-of-motion and rehabilitation activity during the critical first few post-operative weeks at home.

Our design goals included light weight, ease of applying/removing, and no restriction of joint movement or visibility of the healing wound site. We also hoped to make it easier to apply a cold pack, and if possible, monitor the use of that as well. 

Our brilliant apparel consultant, LaJean Lawson, came up with a lightweight harness that strapped to the thigh and calf, leaving the knee exposed. The electronics are hidden within the “smart buckles” that fasten the harness. This was my first experience designing an enclosure that progressed all the way to injection molding. The electronic design using a Bluetooth module and accelerometer sensors was more straightforward, but sensors to monitor the wearing of the device itself and application of the cold pack required some novel ideas. The US Patent Office agreed, finally issuing a patent in 2021 (3 years is par for that course).

Smart Buckle

KneeCoach Assembly

KneeCoach on Manikin Knee

KneeCoach Patent

Shrinking Circuits, Meet Shaking Hands

DIY assistive technology for assembling miniaturized electronic prototypes


When I first started tinkering with electronics in the mid-20th century, most circuits used vacuum tubes. Over the 60 years since then, I’ve been privileged to witness the stunning progress in miniaturization, first with transistors, then basic integrated circuits, all the way to highly complex chips the size of your thumbnail with billions of transistors inside. To keep pace, small passive components — resistors and capacitors — shrank too. To build a prototype of a wearable device with a small size and weight, you have to be able to assemble these minuscule chips and components.

To assemble a circuit, I apply solder paste to pads on a printed circuit board using a laser-cut stencil. A boom microscope provides adequate magnification to see the parts, but the final step requires using a hand-held forceps to pick up and place the tiny components in exactly the right positions on the PC board. By the time I reached 70 years of age, the parts had shrunk to 0.040 x 0.020 inches size, with placement tolerances of 5 thousandths of an inch. And I found I could no longer grip, maneuver, and release the part from the forceps with the rock-steadiness required. Unwilling to give up, I hatched a DIY solution that restored my ability to place components at this new level of precision. More details are available after the photographs.

The first problem was one of crosstalk between two manual processes: moving the part into position over the PC board, and releasing pressure on the forceps at the right moment. The solution was to use a vacuum pick-up device instead of a forceps, and to reassign the function of releasing the vacuum to a foot pedal instead of my hand. From the photos, you’ll see how I started with an inexpensive vacuum pump, then added solenoid valves and associated circuitry to allow foot-pedal control of the vacuum.   

The second problem was that of tremor. With aging some neurons conduct impulses more slowly or even stop functioning, and a servomechanism with excessive delay in its control loop will overshoot and oscillate — and that causes tremor. The solution was to add a stabilizing fixture, with a fulcrum close to the PC board, and damping to reduce the oscillations. The stabilizing fixture was 3D printed, and its fulcrum area and the pickup tool were covered with rubber tubing selected for its damping characteristics.

Sensors for Seniors


Pandemic Project #1: Wireless sensors and gateway for CareBank

The Covid-19 pandemic was devastating to public health, but it also stimulated the development of new technologies hoping to re-establish our social connections. I met Claude Goodman in March 2020, learned of his CareBank project, and gladly took on the challenge of developing improved wireless sensors for that system.

The concept of a Bluetooth Low Energy module and motion sensor was not unusual, but long-range transmission, long battery life, and ease of battery replacement by an elder were more demanding requirements. We used BLE 5.1 and careful antenna design to extend the range and a low data rate to achieve >1yr of battery life. To change the battery, the user just slips off a silicone band (blue band in the rendering) and slides a new coin cell battery into a slot.

The next challenge was reliably relaying the sensor data to the CareBank servers in the cloud. While an up-to-date smartphone with an Internet data connection could do that job, it wasn’t realistic to assume every elder had such a smartphone always operational. As an alternative, I developed a Bluetooth-5-to-cellular gateway prototype. To maximize range, antenna placement was carefully optimized, and the communication link uses positive acknowledgement and retransmission to overcome dropouts. The gateway’s 3D-printed enclosure plugs into a standard USB charging brick, and the combination plugs into a wall outlet like a nightlight.

When it was time to manufacture a prototype run of 75 sensors, we hit one more challenge: the 2021 global semiconductor shortage. I learned how to source components from dwindling stocks in multiple countries and have the PCBs fabricated and assembled overseas. We were lucky; some key chips now have a one year lead time.