Pulse Oximetry Sensor Judges Your Coffee Roast

Breakout board for the MAX30101, which [Zach] used as the basis of his roast gauge. The sensor is at the top edge of the board.
Parts designed and marketed for a specific application can nevertheless still be useful in other ways, and whenever that happens, it’s probably the start of a pretty good hack. Using a sensor for something other than its intended purpose is exactly what [Zach Halvorson] did to make the Roast Vision device, which uses the MAX30101, a sealed optical sensor intended mainly for pulse oximetry and heart-rate monitoring.

[Zach] is instead using that sensor to measure the roast level of coffee beans, and assign a consistent number from 0 to 35 to represent everything from Very Dark to Very Light. Measuring a bean’s roast level is important to any roaster seeking accuracy and consistency, but when [Zach] found that commercial roast gauges could easily cost over a thousand dollars, he was sure he could do better.

[Zach] settled on using a Sparkfun MAX30101 breakout board to develop his device, and Sparkfun shared an informative blog post that demonstrates how making hardware and tools more accessible can help innovative ideas flourish. The Roast Vision device has a 3D printed enclosure, and a simple top-loading design with an integrated sample cup makes it easy to use. One simply puts about a teaspoon of finely-ground coffee into the sample cup, and the unit provides a measurement in a couple of seconds. Fortunately the sensor works just fine though an acrylic window which means the device can be sealed; a handy feature for a tool that will spend a lot of time around ground coffee.

The joys of fresh roasted coffee is something that is perfectly accessible to those making small batches at home. There are commercial options for small roasters of course, but should you wish to go the DIY route, check out our own Elliot Williams’ guide on making a low-cost DIY roaster.

Hackaday Prize Entry: A Complete Suite Of Biomedical Sensors

The human body has a lot to tell us if we only have the instruments to listen. Unfortunately, most of the diagnostic gear used by practitioners is pricey stuff that’s out of range if you just want to take a casual look under the hood. For that task, this full-featured biomedical sensor suite might come in handy.

More of an enabling platform than a complete project, [Orlando Hoilett]’s shield design incorporates a lot of the sensors we’ve seen before. The two main modalities are photoplethysmography, which uses the MAX30101 to sense changes in blood volume and oxygen saturation by differential absorption and reflection of light, and┬ábiopotential measurements using an instrumentation amplifier built around an AD8227 to provide all the “electro-whatever-grams” you could need: electrocardiogram, electromyogram, and even an electrooculogram to record eye movements. [Orlando] has even thrown on temperature and light sensors for environmental monitoring.

[Orlando] is quick to point out that this is an educational project and not a medical instrument, and that it should only ever be used completely untethered from mains — battery power and Bluetooth only, please. Want to know why? Check out the shocking truth about transformerless power supplies.

Thanks to [fustini] for the tip.