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Modeling and Making

CAD, 3D printing, electronics, robotics, woodworking

Mark Leavitt
In 1960s, Grand Tour, Modeling and Making, Radio Daze, The Sound of Music

Adventures in Audio and Engineering

1967-1971

From ’67 to ’71 I was attending the University of Arizona toward a BS in Electrical Engineering. My interest in ham radio had faded, replaced by a fascination with sound and audio engineering, and somehow I found time to work several side jobs while still in college.

KXEW-AM had landed an FCC license to add an FM signal. They promoted me to Chief Engineer and had me supervise the purchase and installation of a 5 kW FM transmitter and a second broadcasting studio. This was great fun for an 18-year-old nerd! To avoid the expense of adding a second full-time DJ, we installed one of the early “automated” radio studios, with reel-to-reel tape recorders and robotic drums of tape cartridges. With PCs not yet developed, this ran on banks of telephone stepping relays and was programmed with a telephone dial. You can probably guess that this Rube Goldberg contraption did not survive for long.

It was around this time that ICs (integrated circuits, or “silicon chips” to the layman) became available to hobbyists and experimenters. I wanted to try building a circuit with both analog and digital ICs, so I designed and built a compact automated studio console for KXEW’s remote broadcasts. This was my first “professional” electronic project. Operational amplifier ICs served to mix audio from a microphone, two turntables, and two cassette playback decks. Digital logic ICs automatically started and stopped the turntables and decks when you pushed a single button.

To protect the setup in mobile use, I also built a custom, padded “roadie” case from plywood. Now I can see that this project was the precursor of two of my lifelong hobbies, electronics and woodworking.

Around this time, I learned that a new recording studio had opened up in Tucson. I dropped in on a whim to see if they had any openings. Forster Cayce, owner of Copper State Recording Studios, was always looking for technical help, so he graciously gave me the grand tour. His studio had a brush with greatness, doing early sessions with Alyce Cooper and Linda Ronstadt, but I never met anyone famous. I mainly cleaned and aligned the massive Ampex multitrack recorders, and occasionally helped with roadie duties. But I eagerly absorbed lots of new knowledge about sound and recording. And I took advantage of their commercial discounts to customize my home stereo with massive studio-quality Altec speakers. As I entered my final year of college, I thought I was headed for a career in audio engineering. I was wrong.

Mark Leavitt
In 1970s, Grand Tour, Modeling and Making, Radio Daze

The Seventies in Silicon Valley

1971-1977

In Spring 1971, companies visited the U of A campus in search of new EE grads. With Vietnam and the Cold War raging on, it was defense companies making the most attractive offers. I was about to accept an offer from MIT’s Lincoln Laboratory, but a boutique Silicon Valley defense contractor — Electromagnetic Systems Laboratories (ESL) — outbid them by throwing in full tuition for grad school at Stanford including time off with pay when attending!

After graduation, I arrived in Sunnyvale with my worldly possessions in a U-Haul behind my VW beetle. The photo shows me and my first wife, Susie, in front of a condo we’d just purchased in the crazy Bay Area housing market. In 1975 we had to camp outside a development sales office for 7 days and nights to buy our first tract home.

Finding a direction in direction-finding

At ESL I started work in the Antenna Department, designing antenna systems for radio direction-finding systems on reconnaissance aircraft. First, an accurate scale model of the aircraft was built from aluminum. Then, we fabricated working scale models of the antennas, often an inch or less in size, and mounted them. The finished model with antenna arrays was tested in an anechoic chamber to measure the radiation pattern and other characteristics of the antennas.

In case an engineer might be needed onboard during testing, I and a few other engineers went through hypobaric/rapid-decompression training. That was an unforgettable experience, fortunately never subsequently needed. I’m surprised that almost 50 years later, a version of this reconnaissance plane is still being flown by the Air Force.

Graduate studies at Stanford

While playing with model airplanes was fun at ESL, I was also engaged in the serious task of completing an M.S., and then a Ph.D., at nearby Stanford University. The STAR (Space, Telecommunications, and Radioscience) lab attracted me, and it was an enormous privilege to have Prof. Ronald N. Bracewell as an initial advisor, and later Prof. Robert Helliwell as I focused on my dissertation.

My dissertation covered the development of a specialized receiver for tracking and performing direction-finding on VLF (very low frequency) radio signals called whistlers. Fans of technologic history can find out more in Don Carpenter’s epic memoir here: The Early History of Very Low Frequency (VLF) Research at Stanford

I thought life would be simpler once I completed my Ph.D. work. And once again, I could not have been more wrong…

Mark Leavitt
In 2000s, Grand Tour, Modeling and Making

Building A Woodworking Shop

2007-2010

Preparing to Retire ReWIRE

Woodworking had been a casual hobby ever since wood shop in high school, but I’d never really had the space it required until we moved to the farm. As retirement approached, I got deeply involved in designing a woodworking shop inside a corner of the barn. True to form, I made mechanical and electrical drawings of everything before I pounded the first nail, and researched the advantages of every machine tool before buying it.

Building the shop was my first real carpentry project, and I had to learn as I went. The electrical part was easier: ample 220V power, heat and A/C, and a vacuum sawdust collection system that activated automatically with the tools. The pictures below show some of the features of the shop.

For raw woodworking material, I hoped to draw upon our orchard of Black Walnut trees. They were 80 years old and a couple of them fell over each year. After cutting the trunks to 3-4 foot lengths, I hauled them to a shed for drying, and rigged up a home-built milling sled for my bandsaw. While I was able to produce some boards, the over-aged wood was full of internal cracks and warped badly as it dried. It was a disappointment but a valuable learning experience.

Framing the shop

Sheathing woodworking shop

Workbench area

Shop corner with dust collection system

Dust collection control circuitry

Router table

Miter sled and cart

Panel cutting fixture

Farm entrance and Black Walnut orchard

Hauling logs for drying

Logs drying in shed

Milling sled

Sawing walnut board

Mark Leavitt
In 2010s, Grand Tour, Modeling and Making

Woodworking Projects

2010-2015

With my retirement from full-time work at CCHIT in 2010, it was time to rewire — an opportunity to explore new pursuits and rediscover old ones. With my newly completed workshop ready, I immersed myself in woodworking, something I’d always enjoyed but never had the time and space really needed.

I started with smaller projects, such as bird feeders, cookbook holders, and jewelry boxes, then built my bandsaw skills by helping my grandson Ryan fabricate a custom subwoofer enclosure for his car. But before cutting up expensive furniture hardwoods, I needed more confidence in my designs. Fortunately, along came SketchUp, Google’s free computer-aided design (CAD) software. It was immensely satisfying to design a furniture piece in CAD, preview and refine its appearance on screen, then finally mill, assemble, and finish the project. There are some examples in the gallery below.

Bird Feeder

Modeled on Italian opera house

Cookbook Holder

Mahogany and acrylic

Jewelry box

Black Walnut (from our orchard!)

Custom Subwoofer

Laminated stack cut out on bandsaw

Custom Subwoofer

Top and bottom relaminated

Custom Subwoofer

Finished, installed with grille

Sewing Table

Oak with drop leaf and machine recess

Home Theater Console

Modeled in SketchUp

Home Theater Console

As constructed

Blanket Chest

SketchUp model including fabric

Blanket Chest

As built

Mark Leavitt
In 2010s, Grand Tour, Health Informatics, Inventions and Patents, Modeling and Making, Wearables for Health

Quantified Self

2011-2018

After experiencing a cardiac event in 2007, I became intensely interested in the science of health behaviors and habits, and began experimenting with technology to support self-tracking and self-improvement. In 2011, I discovered Portland’s local Quantified Self meetups, eventually becoming one of the QS organizers, and giving presentations at their national and international meetings. In a QS presentation, an individual must describe their own self-tracking experiments, reporting three things:

  • What did you do?
  • How did you do it?
  • What did you learn?

This first presentation was delivered at the worldwide QS Conference in Amsterdam.

This second presentation describes my HealthESeat project, an effort to make “seat time” less harmful by encouraging me to exercise my legs while performing computer work.

HealthESeat was a “full stack” project. It included furniture modifications, proximity and rotation sensors, an LED biofeedback light, an Arduino microcontroller, and finally PC software to accumulate data and present visualizations of trends over time. Later, I added an EKG monitor for heart rate variability measurements.

I’ve found Heart Rate Variability (HRV) to be one of the most interesting physiological measurements. Research has associated it with physical health as well as psychological resilience.  I’ve experimented with ways to measure it — using either EKG or PPG biometric sensors — and ways to use it as real-time biofeedback, as well as long term tracking of trends, as described in this QS presentation from 2015.

I’ve seen benefits from my self-tracking efforts, but an even greater benefit has come from meeting such interesting people in the QS community. These associations planted the seeds for my post-retirement business, Wearable Health Labs LLC.

Mark Leavitt
In 2010s, Grand Tour, Health Informatics, Inventions and Patents, Modeling and Making

This could be the start of something big…

2012-Now

The Startup Ecosystem: mentoring, investing, incubators and accelerators

Startups — newly founded companies — are prized as engines of economic growth. While Oregon’s “fertility rate” hasn’t approached that of the SFO Bay Area, an impressive number of companies have started here. This Silicon Forest Universe chart, circa 2002, illustrated how as a handful of Oregon tech companies grew large, then spawned constellations of new startups — sometimes as formal corporate spinoffs, but more often just founded by former employees of the large companies — and the cycle continues.

Soon after I founded MedicaLogic, I was fortunate to be joined by veterans of Mentor Graphics; a decade prior to that, Mentor had been founded by some former Tektronix employees. That’s one pathway for talent, but there’s much more to the startup ecosystem.

My friend Rick Turoczy, whom I was privileged to have working with me at both MedicaLogic and CCHIT, is now a leader in Portland’s startup ecosystem. If you want to know what’s happening there, Rick’s SiliconFlorist blog is the place to go.

But Rick hasn’t just been writing about startups; for almost a decade he’s been helping them grow, as head of the Portland Incubator Experiment (PIE). I signed up as a mentor, and I’ve lost count of how many entrepreneurs I’ve enjoyed talking with as a result of that connection. In 2013, I was a mentor for the Nike+ Accelerator by TechStars and I’ve continued a relationship with my mentee from there, Sprout at Work, now a leader in digital corporate wellness services.

When I work with startups, sometimes I make a modest “angel” investment along with an advisor role, but only when I believe the company can have a positive impact on human health. In many cases I offer technical consulting to worthwhile startups pro bono for the simple joy of it, and there are several examples in my later posts.

Mark Leavitt
In 2010s, Goodies for Oldies, Grand Tour, Health Informatics, Inventions and Patents, Modeling and Making, Wearables for Health

Badges of Honor

2015-2018

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

Mark Leavitt
In 2010s, Doctor, Doctor!, Goodies for Oldies, Grand Tour, Health Informatics, Inventions and Patents, Modeling and Making, Wearables for Health

Filling a KNeed

2016-2021

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

Mark Leavitt
In Grand Tour, Inventions and Patents, Modeling and Making, Wearables for Health

Lending a Hand

2017-2018

3D Printing a Low-Cost Prosthetic Hand

I began using 3D printing for my wearable device prototypes, sending designs to a service such as Shapeways or contracting with a local firm run by biomedical engineer Rachel Dreilinger. But I wanted to iterate on my designs more quickly and at lower cost, so in 2017 I built my own 3D printer from the Prusa i3 MK3 kit.

I discovered there’s a learning curve to 3D printing, but fortunately there’s also a massive online community of “makers” adopting the technology — over 1000 right here in Portland! –so there has been plenty of help available. One community, e-Nable, has tackled the challenge of 3D printing free prosthetic hands for clients in lower medical resource environments. It’s well organized, with an informal certification program for fabricators, and the accompanying video was my application for approval.

Designing and Printing a Robotic Gripper

As 3D printing became easier, public libraries stepped in to provide access to this technology. The Hillsboro Public Library built a well-equipped “Collaboratory” makerspace where I served as a volunteer, teaching a class and helping patrons use the devices available. A fellow volunteer had taken on an interesting project — designing and fabricating a sophisticated robotic arm — and given the daunting size of the project, he welcomed my offer to design a gripper to go at the end of the robotic arm. You can learn about my efforts in the associated video here.

Mark Leavitt
In 2010s, Grand Tour, Inventions and Patents, Modeling and Making, Wearables for Health

Hearts on Fire

Cardiac Stress Monitoring and Notification for First Responders

2017-2020

After retiring from full-time work at CCHIT, I accepted a volunteer role closer to home, as an Advisory Board member for the Berglund Center at Pacific University. Following several years serving as a judge on their annual Inspired Ideas competition, I was asked in 2017 if I could take on a bigger role: mentoring their winning team of students to guide them from their raw concept to a working prototype.

The team of psychology graduate students had been studying and treating stress in firefighters. They, and I, were surprised to learn that heart attacks — not fire, smoke, structure collapse or falls — were the leading cause of on-the-job deaths in firefighters. The students wanted to equip firefighters with heart monitors that would measure and relay their stress levels to the incident chief, but lacked any engineering training or resources. I liked this challenge immediately and accepted a role as their engineering consultant.

HeartMic - breadboard

HeartMic - first prototype

HeartMic - second prototype assembly

HeartMic Prototype

HeartMic - prototype rendering

HeartMic - demo software

Wearable physiologic monitors were an already well-established technology, appearing in smartwatches and fitness bands. But there was a showstopper: their low power 2.4 GHz Bluetooth transceivers could not achieve the communication range and reliability needed at an incident site, and we could not rely on a consumer smartphone as a relay in this demanding application. Then the proverbial light bulb of invention clicked on: every firefighter already had a robust wireless communication device: a UHF portable radio, controlled by a shoulder-worn speaker/microphone. We conceived of a “smarter” speaker/microphone unit that included a microprocessor and Bluetooth transceiver to receive the physiologic data. Heart-rate based alerts could then trigger a synthesized voice message. The alert could be played locally over the speaker to notify the firefighter him/herself, and then — if more urgent — it could activate the push-to-talk circuit and be transmitted over the portable radio’s network to the incident commander.

I started with a breadboard consisting of an Arduino-compatible microcontroller, an MP3 player, a Bluetooth module, and relays to trigger the PTT and switch the audio. The students’ jaws collectively dropped when they saw their idea actually working, despite the ugly breadboard implementation. The next step was to shrink the size by designing a custom PCB and a 3D-printed case, creating a first prototype that could at least fit in your hand. For the next iteration — now called HeartMic — I plunged into C programming to get all the necessary code running on the microprocessor included in the Bluetooth chip. With the separate microcontroller eliminated, the device was slimmed down to fit in the palm of one’s hand. The finishing touch was laptop software, communicating via Bluetooth, to configure HeartMic with specific alert levels for each firefighter. We demonstrated the system at a fire station in Washington state, and applied for a patent which was granted in 2021. The students truly had a “full stack” product development experience!

Mark Leavitt
In 2020s, Goodies for Oldies, Grand Tour, Inventions and Patents, Modeling and Making, Wearables for Health

Shrinking Circuits, Meet Shaking Hands

DIY assistive technology for assembling miniaturized electronic prototypes

2020

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.

Size of 0402 SMT component

Assembling with forceps

Vacuum pump disassembled

Vacuum pump modified with foot pedal

Vacuum pickup with stabilizing fixtures

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.

Mark Leavitt
In 2020s, Goodies for Oldies, Grand Tour, Health Informatics, Modeling and Making, Wearables for Health

Sensors for Seniors

2020-2022

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.