There are many sensible well being monitoring gadgets in the marketplace at the moment, however the additional tech they pack in could make them fairly costly. If you have already got completely useful tools, like a blood stress monitor, changing it simply to get Wi-Fi connectivity looks as if a waste. Maker Tomasz Burzy determined to take a unique method by turning an odd, secondhand blood stress monitor into a sensible system with an ESP32-CAM and a little bit creativity.
The mission began with an affordable blood stress monitor bought on eBay. Burzy needed to routinely add measurements to a regionally hosted well being monitoring utility with out having to manually enter the numbers. His preliminary plan was to faucet into the monitor’s electronics and extract the measurements immediately, however that proved to be extra difficult than anticipated.
The unique {hardware} (📷: Tomasz Burzy)
After opening the system, Burzy found a circuit board populated with an Epson microcontroller, stress sensor, and the electronics answerable for working the air pump and valve. Utilizing a cheap logic analyzer, he started probing the board in quest of the information being despatched to the show.
Though he managed to seize uncooked stress sensor readings, the ultimate systolic and diastolic values have been calculated internally by the microcontroller. He even experimented with writing his personal blood stress calculation algorithm with help from AI, however the outcomes weren’t correct sufficient to be helpful.
Relatively than proceed reverse-engineering the proprietary calculations, Burzy got here up with a a lot less complicated (if considerably clumsy) answer: level a digicam on the show and browse the numbers immediately.
A calibration instrument helps to learn the 7-segment show (📷: Tomasz Burzy)
An ESP32-CAM module serves because the brains of the improve, capturing photographs of the monitor’s LCD and transmitting measurements over Wi-Fi. Nevertheless, as a substitute of counting on computationally costly optical character recognition, the firmware takes benefit of the show’s seven-segment digits.
Every digit consists of seven segments that may be illuminated in several mixtures to symbolize numbers. By checking predetermined places inside these segments and figuring out whether or not they’re illuminated, the ESP32 can reconstruct the displayed systolic stress, diastolic stress, and pulse price.
To maintain the digicam correctly aligned, Burzy designed a customized mounting arm in Fusion 360 and 3D-printed it. He additionally found that reflections from the monitor’s clear show window interfered with detection, so he eliminated the offending plastic.
The completed construct contains two extra buttons for choosing between person profiles, together with an LED that confirms the choice. The ESP32-CAM may enter deep sleep between measurements, waking routinely when the monitor’s begin button is pressed.
As soon as a measurement is full, the ESP32 reads the show and uploads the outcomes to Burzy’s non-public well being monitoring utility. The open supply firmware additionally helps sending measurements to Dwelling Assistant, Node-RED, or different HTTP endpoints.
Burzy has printed the firmware, digit-mapping utility, and 3D-printable digicam mount, making it doable to offer different standard blood stress screens the same improve. Simply do not forget that the digicam can sometimes misinterpret a digit, so vital measurements ought to all the time be checked towards the unique show.