Hardware
3To reiterate (since the previous blog took a sudden turn), the main purpose of this blog is to document an experience that will hopefully be a realistic, relatable diary for those who have an idea and want to create a product but don’t have extensive knowledge in ECE/coding. The previous blog explored the idea of using LLMs/AI to speed up the research process, which will very likely be a resource that I use to do more data collection on research articles or other, more casual resources as well.
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Focusing first on the hardware, this can range anywhere from the Kiosk at your local Sunright to the ID card reader at a library. Both of these items take some sort of input and send it somewhere else that it is needed, usually to a display of some sort. To get a better look at what I’m dealing with, my first instinct was to dissect. In my case, I wanted to do something with a digital sphygmomanometer. To give everyone an idea of “final destination,” I want to learn how to create something similar to a bluetooth digital blood pressure monitor where u can see the measured vitals on the screen and easily maneuver the data. I took one that was lying around in my house and took it apart. To my surprise, there were more parts than I expected. First, there was a mechanical pump that generated the air to be pumped into the cuff. There was also a valve that regulated the air pressure, called a solenoid valve, which distributes the air into the cuffs per pump (to manage and keep track of the pressure in the cuffs). These are all controlled by the microcontroller (MCU), which has a variety of parts on it, including an analog to digital converter (ADC). This converts binary to something that is more high level for us humans. This isn’t anywhere close to an exhaustive list, but essentially the MCU gives commands to the pump and valve, which interact with the person using it. The information comes back and spits out a reading that is in actual numbers that aren’t just 1’s and 0’s.
While looking at some circuit diagrams, I found something that could be potentially useful.
At first, I looked at something called an MCP6N11 Instrument Amplifier because I saw that it was just after the pressure sensor, but I found that it was just to amplify the signal that was being received (most likely just to improve accuracy of the readings?). Instead, I looked at the pressure sensor, which was directly connected to it. Unfortunately, everything looks hopelessly similar, so I had a hard time picking apart the pieces. Eventually, the pressure sensor that I looked up online looked pretty similar to the one that I had in front of me, so that was my best bet for the pressure sensor. The sensor feeds into the instrument amplifier, which feeds into a digital to analog converter (DAC, the “reverse” ADC), and finally back into the ADC. The ADC then displays the numbers via the liquid crystal display (LCD). I was thinking instead of feeding back into the ADC, do bluetooth blood pressure readers just skip the step and transmit the data to another device, where their ADC makes the readings readable? Following this, we could theoretically use this as a port to our device of choice.
