Infrared CO2 measurement





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Cornea glare test instrument for MEEI


This custom built instrument will allow Dr. Rony Sayegh at the MEEI (Mass Eye and Ear Infirmary, Boston, MA) to improve the sight of his patients. Dr. Sayegh has developed a cornea implant called the Boston KPro (here’s a link to the wiki article about it: In order to continue improving this design, we supported Dr. Sayegh with this instrument. Using a carefully aligned LED source and a rotational camera mount, in a light tight enclosure, the glare of various new cornea implant designs can be tested and evaluated.

We were able to deliver a custom instrument for reasonable cost and effort by using a combination of custom parts (mostly laser cut plexi from Danger Awesome in Cambridge, a link to their website here: ) and off the shelf mechanical/optical components from Thor Labs (





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LED current source based on LT3080, the modern LM317 replacement part, runs off USB or 9V or any voltage in between

This 20mA current source will operate from a USB 5V power supply. Using the LT3080 linear regulator makes it easy to get good voltage headroom. Only 200mV is needed in this version to sense the LED current – the old venerable LM317 required 1.25V just to get started – and that’s not including any drop-out voltage of the pass transistor.

There's no need for a heatsink since the regulator does not dissipate much power.










Here’s a link to the schematic, in pdf format, showing some details of the voltages and operating ranges.



This shows the simple package for the LED current source, ready for use in testing the spectra or providing a constant light source on our optical bench.

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Blue LEDs make healthy babies – Firefly Phototherapy from Design That Matters

At an early stage in this project, Pete provided measurements and guidance about the most effective LED optics for the jaundice cure for new born babies. Full project description can be found at the Design That Matters website here. Uniform light with the fewest LEDs, to reduce cost and insure effective treatment.

Project Firefly: Infant Phototherapy. Best use of blue LEDs we can think of.


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Eye exam using a smart phone, and some plastic optics – the NETRA project

Pete has been working with some folks at the MIT Media Lab, in particular the Camera Culture Group of Ramesh Raskar. Using the display on the smart phone, and some pinholes and plastics, you can interact with the phone and measure your prescription and astigmatism. Link to project description at MIT Media Lab

There is a new start-up spin off company called Eye-Netra, that can be found here.

Here’s Pete demonstrating the clumsy kit that Eye Netra will replace:

Here's the lens kit you'd need without the modern Eye Netra for an eye exam. Please follow the instructions on Pete's t-shirt in the photo.

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Energy Harvesting – battery-free radio

We’re working on some energy harvesting projects – and we learned about this amazing project – a radio powered only by the sound of the voice of the person talking at the transmit end.

El Silbo, voice powered radio design by MJ Rainey

This was able to transmit 150 miles with NO batteries at all. And no ‘super caps’ either. Just the transient power of his voice. Michael Rainey provides a schematic here:  Schematic of voice powered transmitter, El Silbo.

The trick for using a speaker as a microphone to absorb sound wave power is to get a good step-up transformer. The speaker has current, but little voltage, even into a high impedance. Of course, you can get more power output using the tin can approach, demonstrated in this video:

AA1TJ voice powered TX transatlantic attempt. No batteries.

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high voltage testing of 208VAC phase controller used on semiconductor production equipment

This phase controller uses the tried and true back to back SCR technique. It’s and old unit but still in service, partly due to our repairs and system debug. About half the gear in the photo is our test jig. Watch out for ‘flux doubling’ when you turn on/off that big toroid transformer! We kept blowing the 20A breaker until we set up the variac on our bench set up.

Phase controller power supply under test on our bench. The light bulbs provide a test load, the toroid allows us to use 110VAC to supply the test unit with 208VAC.

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client action photo

Here’s a couple of our clients puzzling over some lens test data. This was an exciting day, to see this huge lens tested! The puzzling was over by the end of the day, but this is a better action shot.

Perplexed clients puzzled over pixel positioning problems.

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photos of recent work

a tiny slide projector using a loupe and an LED, bench tested at our shopHere’s a photo of an LED light source and image projector under test:







And here’s a rotary stage we use to test corneas and LEDs – to determine the angular spread of light or scatter:

Marked in 1 degree increments this rotary stage can allow tests of angular light spread of LEDs.

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plausible, feasible, tangible

What we do always involves these three phases:

Is it plausible? Does your idea violate any known physical laws? Are you asking for a new light bulb that has 110% efficiency? If it passes the plausible test, we go to the next phase:

Is it feasible? Can your product be made, given a reasonable budget in a reasonable time frame? Often the ‘existence proof’ of a similar technology or device can help us answer this with minimal effort. Or we build a prototype to test the most tricky aspect – this becomes an object that can be tested, used, and evaluated, which brings us to the third phase:

Here it is. It’s tangible. A prototype, a ‘proof of principle’, a first example that shows what kind of performance and cost can be expected. Something you can use. This is a way to find the ‘slap on the forehead’ mistakes, and find them early in the project. Before you waste a lot of time, effort money on tooling, marketing, etc.

In the next weeks I’ll be writing about more specific examples of this process flow.

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