The Future of Open-Source Hardware for Medical Devices

Medical technology is changing at a rapid pace, but regulatory compliance is also becoming increasingly harder. Regulatory compliance can act as a barrier to innovation, but it is a necessary check to ensure quality medical care. For small companies, aligning innovation with regulatory compliance can only help.

Fergus Dixon

When designing any new product, the FDA-recommended process is a great reference. First, the design input requirements must be written down. After the device has been designed and prototyped, verification and validation (V&V) will ensure that the device meets the design input. The device is then documented, creating the design output or device master record (DMR). Each device made is checked against the DMR and documented in the device history record (DHR). So all the details on how to make the device are contained in the DMR, and the results and traceability are recorded in the DHR.

My company recently asked an overseas company to design and manufacture an existing product. After many e-mails, the overseas company managed to build a working unit and immediately requested an order for 1,000. Before ordering even one unit, there was the matter of V&V. So what is V&V? Verification is the act of ensuring that the circuit acts as it should, as the circuit designer intended. This involves testing to a predetermined criteria, where the pass/fail is clearly defined. Testing happens by varying the inputs and checking the outputs to test the device as close to 100% as reasonably possible. When the inputs fall outside a normal range (e.g., a 10-VDC instead of 12-VDC battery voltage), the device must still work or it must provide a message showing why the device will not work (e.g., low battery light). Validation is the act of ensuring the circuit works as the customer or patient requires. This involves field testing, feedback, and rework—lots of it.

Working for medical device companies can be very rewarding. Smaller companies tend to work at the cutting edge. Larger companies are more secure and have stable products, but they can be less agile. With one company, we had a device that used smart batteries. During testing, we discovered that the batteries would not charge below 15ºC. After many meetings and e-mails to the manufacturers, the problem went to management, who decided to change the manual to say: “Do not charge below 15ºC.” Smaller dynamic companies can attract the best scientists, which is great until a connector fails and there is a roomful of highly intelligent people with no soldering iron experience. Every technology company can benefit from having at least one experienced technician or engineer. A few hours spent playing with an Arduino is a great way to get this experience.

What about open-source hardware (OSHW) for medical devices? For home hobbyists and students, OSHW is great. There is free access to working circuits, programs, and sketches. C compilers, which once cost several thousand dollars, are mostly free. For the manufacturers, the benefits are plenty of feedback, which can be used to improve products. There is one roadblock, and that involves the loss of intellectual property (IP), which means anyone can copy the hardware. Creative Commons has addressed this with an agreement that any copies must reference the original work. Closed-source hardware can also be good and present fewer issues with losing IP. Apple is a great example. Rather than use feedback to improve products, it makes smart decisions about future products. The iOS vs. Android battle can be viewed as a closed-source vs. open-source struggle that still hasn’t produced a winner. Medical devices and OSHW will have to meet up sometime.

Fergus Dixon’s embedded DNA sequencer project (Source: F. Dixon)

What about the future of medical devices? Well, the best is yet to come with brighter organic light-emitting diode (OLED) displays, a multitude of wireless connectivity options (all using the serial interface), and 32-bit ARM cores. DNA is gradually being unlocked with even “junk DNA” becoming meaningful. The latest hot topics of 3-D printing and unmanned aerial vehicles (UAVs) have direct medical applications with 3-D printed prosthetic ears and medical nanorobotics ready to benefit from UAV technology. Using a new sensor (e.g., a gyroscope) now means visiting an online seller such as Pololu, which offers ready-built development kits at reasonable prices. A recent design was a manually assisted CPR device project, which was abandoned due to lack of funding. How great would it be to have a device that could not only improve the current 10% survival rate with CPR (5% without CPR) but also could measure a patient’s health to determine whether CPR was helping and, even more importantly, when to stop administering it? Now that would be a good OSHW project.

Member Profile: Gordon David Dick

Gordon Dick

Location: Stony Plain, AB, Canada (Stony Plain is suburb of Edmonton, home of the Oilers)

Education: MS, the University of Saskatchewan in Saskatoon, SK, Canada

Occupation: Gordon is semi-retired. He used to be an Electronics Technology and Computer Engineering Technology instructor at the Northern Alberta Institute of Technology in Edmonton.

Member Status: Gordon says he used to have Circuit Cellar issues dating back to 1995. “We were getting issues under the ‘college program’ then,” he explained. Later, his department subscribed to the magazine and the issues came directly to Gordon. Then he obtained a personal subscription. “I still have my paper copies containing my own articles. And we bought the CDs to get all the back issues.”

Technical Interests: Gordon has always been interested in electronics, both as a hobby and as a profession. He focused first on audio, then turned to microcontrollers. He has built a few microcontroller-based instruments, some of which have been the topics of his Circuit Cellar articles. “For a time, I was involved in building microcontroller-based dog training equipment. I built a microcontroller-based weather station, which I also wrote an article about. I have several microcontroller-based projects in my home that are specific to my needs. My cold-room temperature controller is microcontroller-based, for example.”

Most Recent Embedded Tech-Related Acquisition: Gordon bought a SparkFun Electronics FG085 frequency generator kit.

Current Projects: He is working with a Freescale Semiconductor MPL3115 pressure/temperature I2C transducer for his weather station. “It has amazing barometric pressure resolution,” Gordon explained.

Q&A: Michael Hamilton (Engineering and Entrepreneurship)

Michael Hamilton

Michael Hamilton has been designing microcontroller-based systems for 25 years. Over the past 10 years, he has spearheaded two companies: A&D Technologies, which supplies wireless temperature and humidity controllers, and Point & Track, which provides data-gathering apps and other business intelligence tools. In January, I interviewed Michael about his longtime interest in electronics, his first microcontroller design, his award-winning Renesas Electronics RL78 project, and his praise for 3-D printers.—Nan Price, Associate Editor

NAN: Where are you located?

MICHAEL: Lewisville, TX.

NAN: Give us some background information. Did anything specific spark your interest in engineering?


MICHAEL: My dad was an instrument repairman for Ashland Refinery in Canton, OH. As part of his training, he brought home his electronics trainer along with the instruction manuals.

When I was 13, I was interested in explosives and I needed an electronic timer for safety reasons. I studied his coursework and figured out how to build a timer using the famous 555 timer chip.

My family had a Christmas tree farm, where I spent many hours working. This led me to the decision that I needed to go to college instead of doing hard labor. I ended up going to Ohio University in Athens, OH, to study chemical engineering.

The reason I chose chemical engineering was, during high school I entered the science fair with a project called the “Distillation of Crude Oil.” This project was very successful as I made it to the state science fair and won lots of prizes.

Tektronix 485 oscilloscope

After I graduated from college, my interest turned back to electrical engineering and I started reading every book I could find on electronics. I remember my first big electronics purchase was a Tektronix 485 oscilloscope.

While working for Ashland Chemical in clean room environments, I realized there was a need for an accurate humidity controller. This led me to design my own temperature and humidity controller and form my first company, A&D Technologies ( in 2003.

NAN: What types of products and services does your company provide?


MICHAEL: A&D Technologies supplies wireless temperature and humidity controllers (e.g., HTC100) along with custom control panels. Using the latest technology, the control panels communicate to the outside world using SMS texting via cellular modems and e-mail via Ethernet.

Along with another partner, we created a new company, Point & Track (, which provides custom data-gathering apps for mobile devices such as iPhone and Android, secure database management, and business intelligence tools used to analyze collected data. The company also provides the ability to export geographic information system (GIS) data directly to customer-owned databases.

NAN: What type of work did you do prior to A&D Technologies and Point & Track?

MICHAEL: I was a project engineer who designed and installed automated equipment such as a fully automatic coiling systems using an ABB robot.

NAN: How long have you been designing microcontroller-based systems?

MICHAEL: Twenty-five years.

NAN: What was the first microcontroller you worked with?

MICHAEL: It was Microchip Technology’s PIC18F84. I designed a laser viscometer that was used to determine the viscosity of plastic resins while working for Ashland Chemical in Los Angeles, CA. I learned how easy it was to provide precise timing and work with digital I/O. It was so much easier than trying to work with individual integrated circuit (IC) chips.

NAN: What is the worst problem you have encountered with embedded microcontrollers?

MICHAEL: By far, the worst issue has to do with electromagnetic interference (EMI) from nearby devices, such as switching of solenoids or transformers. An extensive amount of time is spent designing PCBs so they will be immune to the external environment. Things like ground planes, metal oxide varistor (MOVs), transient voltage suppressors (TVSes), and capacitor/resistor networks are used to minimize the susceptibility of the microcontrollers, but it seems like you can never predict the environment for these kinds of issues. Maybe someone will write an article discussing these issues and how to prevent them.

NAN: Any recent tech purchases?

MICHAEL: I recently purchased a Rigol Technologies DSA-815-TG spectrum analyzer. This device is a must have, right behind the oscilloscope. It enables you to see all the noise/interference present in a PCB design and also test it for EMI issues.

NAN: Do you have any other unique tools on your workbench?

CNC Machine

MakerBot 3-D Printer

MICHAEL: I have a three-axis CNC machine and a MakerBot 3-D printer. I use the CNC machine to cut out enclosures and the 3-D printer to create bezels for LCDs and also to create 3-D prototypes. These machines are extremely useful if you need to make any precise cuts or if you want to create 3-D models of future products.

NAN: What is the fastest way to learn about programming and electronics?

MICHAEL: In the last six months, I have learned the following languages: Arduino, PHP, HTML 5, CSS, MySQL, Android, JavaScript, and jQuery. This was done by watching YouTube videos while exercising at the gym.

NAN: Your project, the Cloud Electrofusion Machine, recently won second prize in the 2012 RL78 Green Energy Challenge. Tell us about your project and your contest-entry process.

Cloud Electrofusion

MICHAEL: The project created an in-expensive and energy-efficient way to weld polyethylene pipe together. Commercial machines cost around $4,000. This machine can be built for less than $200. It utilizes a light dimmer to drop the voltage from 110 to 40 VAC and controls the amount of time that the power is applied to a coil inside an electrofusion fitting. By incorporating a barcode scanner, all the specific properties of the fitting can be easily entered into the microcontroller. Then, after the fusion is complete, all the data is sent to a cloud server via a wireless cellular modem.

The RL78 was very easy to use and program. I really didn’t have many problems with the design.

NAN: Your article “Infrared Radiation Measurement: FFT Double-Beam Infrared Spectrophotometer” (Circuit Cellar 229, 2009) describes a spectrophotometer built around a Microchip Technology dsPIC30F4012 digital signal controller. How does the microcontroller work in the design?

MICHAEL: The project created an instrument to identify chemical substances by using infrared spectroscopy. The dsPIC30F4012 uses a 10-bit ADC to measure the infrared radiation signal that passes through a chemical substance. Then the microcontroller computes the fast Fourier transform (FFT) of the signal. This creates a table of amplitude versus frequency. The amplitude is then scaled to provide a relative transmittance. This information is serially transmitted over USB to a computer for plotting. This USB interface is accomplished using a PIC18F2450.

NAN: Are you currently working on or planning any microprocessor-based projects?

MICHAEL: We are currently working on a cloud fusion logger. This device reads all the data from the welding process in the field and transmits it to a cloud server. Later, the data can be analyzed and reports can be generated. A Raspberry Pi is used as the embedded controller. It is very fast and easy to use since it is based on Linux. We are working on getting the Android operating system loaded so existing code can be used and it will interface well with an Android smartphone, which will be used as the operator interface.

NAN: What do you consider to be the “next big thing” in the embedded design industry?

MICHAEL: One of the issues with embedded controllers is how to maintain the firmware and fix bugs after the devices are installed in the field. Using various wireless technologies, the devices will be automatically updated. Smartphones already use this technology.

CC273: Necessity and Invention

Tom Cantrell wanted to stop fiddling with his sprinklers as he tried to balance conserving water in California and keeping his lawn green. So he asked himself if he could craft a weather-savvy sprinkler controller.

In the April issue of Circuit Cellar, he describes how to weatherize an embedded app. He uses a Texas Instruments MSP430 microcontroller and a WIZnet W5200 smart Ethernet chip to access National Weather Service forecasts and data (p. 36).

Engineer and entrepreneur Michael Hamilton also has found that necessity breeds invention—which in turn can start a new business. “While working for Ashland Chemical in clean room environments, I realized there was a need for an accurate humidity controller,” he says. “This led me to design my own temperature and humidity controller and form my first company, A&D Technologies.”

In our interview, he talks about what he has done since, including founding another company and becoming an award-winning designer in the RL78 Green Energy Challenge (p. 44).

A shift in the timing signal—or jitter—of a digital transmission can adversely affect your high-speed designs. It’s been an issue for at least 40 years, with the advent of the first all-digital telecommunications networks such as PDH. But you may not have dealt with it in your designs. In the April magazine, Robert Lacoste explains how to diagnose a case of the jitters (p. 54).

Jeff Bachiochi isn’t a musician. But he didn’t need to be one to work with the musical instrument digital interface (MIDI), which relays instructions on how to play a piece directly to an instrument (bypassing the musician). In the April issue, he describes the circuitry needed to connect to MIDI communication and display messages between devices (p. 60).

Atmel’s ATmega88 and ATmega1284 microcontrollers are at the heart of the CNC controller.

Also, Brian Millier describes how he built a microcontroller-based G-code controller for a CNC router. Even if you are not interested in building such a controller, you can learn from the techniques he used to provide the multi-axis stepper-motor motion (p. 30).

You also might find Scott Weber’s experience instructive. After placing microcontroller-based devices throughout his home, he found he needed a control panel to enable him to update the devices and check on their operation. He shares his panel’s basic structure and its software design. Its display shows him all the information he needs (p. 22).

While wear and tear affect the reliability of hardware, software reliability is different. Whatever causes software to fail is built-in, through errors ranging from poor coding to typos to omissions. On page 51, George Novacek shares some methods of calculating the probability of faults in your firmware.

Also in the April issue, Bob Japenga continues looking at concurrency in embedded systems. In the sixth article of his series, he discusses two Linux mechanisms for creating embedded systems—POSIX FIFOs and message queues (p. 48).

Finally, “From the Archives” features a 2003 article by Mark Balch about Verilog HDL. He discusses how to use it in your custom logic designs for digital systems (p. 68).

SMD Stencil Reflow Soldering Tutorial

Surface-mount SMD reflow soldering doesn’t have to be difficult. All you need is a solder paste stencil, a hot air gun, and a little know-how. No reflow oven necessary!

Dave Jones, of, covers everything you need to know in the following easy-to-understand SMD stencil reflow soldering tutorial.

The kit is available via Elektor’s partner, Eurocircuits.

The Eurocircuits kit includes all the essential SMT components, circuit boards, and solder stencils.

For SMT info and additional projects, refer to Vincent Himpe’s book, Mastering Surface Mount Technology (Elektor). is an Elektor International Media website.