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Hypoglycaemia (low blood sugar) alert system

A compact Bluetooth device that acts as a safety net for sleeping type 1 diabetics, detecting hypoglycaemia and calling for help.

This project was created on 07/25/2014 and last updated 2 months ago.

Description
Among the many issues and complications that type 1 diabetics deal with on a daily basis is the risk of hypoglycaemia (put simply, low blood sugar) while asleep. On top of the often severe physical consequences of hypoglycaemia, just the risk of it occurring while a diabetic is asleep can itself have significant psychological effects, leading to poor control of glucose levels and impeding independence.

Having seen firsthand the impact type 1 diabetes can have on a person's lifestyle, this system has been an ongoing project of mine on and off for over a year now. It is my attempt at providing a sort of 'safety net' for type 1 diabetics at night.

By measuring temperature and humidity close to the skin, this system aims to detect severe nocturnal hypoglycaemic events. Measurements are taken with a small, battery powered device, which periodically connects to a nearby Android phone via Bluetooth. If an event is detected, a list of emergency contacts are called for assistance.
Details

System Overview

A mobile sensor device contains an ATmega328p, an HIH6131 humidity and temperature sensor, a LIS3LV accelerometer and a SPBT2632C2A Bluetooth module, all powered by a 2.7V LTC4081 switchmode power supply/charger and a 400mAh LiPo battery. The sensor is designed to be worn close to the skin of the diabetic, and detect the heavy sweating that often occurs with very low blood glucose levels.

Every 15 minutes, the sensor module powers up the Buetooth module and connects to the nearby Android phone, uploading all the sensor data for that period before switching the Bluetooth back off to save power. The Android application then sorts through this data, and determines if an alarm is required. If an alarm is triggered, it then works through a list of preset contacts, calling them for assistance until one texts back.

More detail on how the system works can be found in the following project logs:


All code, schematics, and PCB designs developed for this project are free and unencumbered, released into the public domain. It turns out it's actually harder than I thought to declare something completely public domain, but I'm honestly happy for people to do whatever they want with them. No attribution necessary.


Feedback Wanted

While I know several people who are type 1 diabetics, and have designed this system with their input, I’m not a diabetic myself, am certainly not an expert on the subject, and realise that the experiences people have with it can be quite different. One of the main motivations for me posting this project was get input from a wider group of people, and so if there’s anything you read here that doesn’t quite sit right with what you know about diabetes, let me know! 

Project logs
  • Quick update

    2 months ago • 0 comments

    With the deadline for the next stage of the Hackaday Prize looming, a brief update is probably necessary:

    While progress on this project is still ticking along slowly (I'm just bad at continuous project logging), the boards for the next hardware iteration won't be here for another couple of weeks, let alone the deadline in a few hours. As such, I can't show a video of it working, making it a bit difficult to qualify for the next set of judging. On that note, a lot of the other current entries out there look really awesome - I can't wait to see how some turn out.

    Read more »

  • Bluetooth Comms

    3 months ago • 0 comments

    A key part of the current system and how it works is the Bluetooth communication between the sensor device and the Android phone. As a mobile device, the power supply is limited by a relatively small battery. When connecting or sending data, the current draw from the Bluetooth module vastly outweighs anything else in the circuit, peaking around 28 mA and averaging closer to 18 mA. To stop this from quickly flattening the battery, the data exchange is instead periodic, and is adjustable from the Android app. Read more »

  • Hardware Design Breakdown

    3 months ago • 0 comments

    I will admit to committing a cardinal sin of electronic device design - I picked the enclosure before designing what needed to go in it. This is one of the reasons I'm designing another hardware iteration, and had a few implications that can be seen in the current device - there is way too much empty space, the battery is being just slightly compressed, and the USB port is sticking out the large, flat side of enclosure, rather than the edge. Read more »

View all 5 project logs

Discussions

thomas.sanders7777 wrote 2 months ago null point

This is an amazing idea. As a diabetic myself i have woken up with very low blood sugar. sweating is also common not only lows but highs as well, my sweating starts at the moment i start to be too low or very high, so the alarm would be helpful to a diabetic like myself. Anyhow awesome work!!!

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Thomas Wilson wrote 2 months ago null point

I honestly hadn't considered the use for highs as well - the audible alarm is probably much more relevant in that case. In your experience, what would be the best place to try and detect the increase in humidity from the sweating (wristband, waistband clip, in a pocket, etc.)?

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diysciborg wrote 4 months ago null point

Check out this group (sucky that they chose to organize themselves solely on a twitter hashtag but whatever)
http://www.diabetesmine.com/2014/03/we-are-not-waiting-diabetes-innovation-now.html

Lots of good engineers hacking their meters..

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Nick Ames wrote 4 months ago null point

Does the device have an alarm to wake the user if their blood sugar drops too low?

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Thomas Wilson wrote 4 months ago null point

The current software does have an alarm, yes. That said, it often isn't particularly useful - the conditions being detected are the severe, drenching sweat that often accompanies very low blood glucose levels, at which point (according to the diabetics I know) the diabetic is often not capable of responding themselves, and needs assistance from a third party. So far, the primary function of this alarm has been to give the diabetic a chance to stop the alert call going out in the event of a false detection. I'm still drafting the rest of the project entry here - a lot of it is explained there.

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