Advice needed for wearable tech

[Keevashski]

Hi guys
I am about to undertake a project with very little experience in the field and could use some pointers.

Basically, me and a team of 3 others are designing and making a shirt that records heart rate, blood pressure, her real body temp and hydration loss. The sensors for the shirt we can make easily enough but to transfer the data to the pic and then wirelessly transmit this info to a monitor is where I get stuck.

If anyone has any experience with this or any tips it would be greatly appreciated

Thanks very much

[Docara]

HI Keevasheki,

Um! Where to start!

Right, there are many ways to skin a cat!!! And everyone you ask will have a different idea. First of all design is usually an iterative process, the trick is not to make as few u-turns as possible before you get to your solution - be warned.

If I were in your shoes don't even consider a microcontroller at this stage of your project. I would concentrate on finding out voltage levels, current demands, how each of your sensors 'transmit' their data to the outside world and the repetition rate of data transmission. What I'm stumbling about trying to say is the heart rate monitor, I would assume, to be continuous and the moisture rate could be transmitted every minute with and average value. What bit rate ADC will you need - would a standard IC dedicated to the purpose suffice or could you get away with an onboard ADC in a uC. Do you have to use multiplexing, would RF affect anything will the weight of the battery to power everything be an issue etc etc

When you absolutely KNOW what you are dealing with you can then make the decision on the next step in the chain.

Sorry bud I think you have MUCH more electronics to do before this question is relevant.
Matt

[Keevashski]

Cheers for the reply matt

Basically me and my team are just going to buy a heart rate monitor and hydration detector and take the sensors and what we need from them and input them directly into the picboard.
This will only be a prototype so exact measurements aren't necessary but if it simply performs the standard function it will do.

mostly I need help with transmitting the data from the pic to the monitor, we will be using raspberry pi2.

cheers
adam

[Benj]

For transmitting the data you could use Bluetooth or Wifi, both are widely available and low cost and will be easily compatible with the Pi using a USB dongle.

I would recommend the HC05/HC06 modules for Bluetooth and the ESP8266 Module for Wifi.

Both Bluetooth and Wifi have their good and bad points so you need to decide which would best suit your application.

Bluetooth needs to be paired, Wifi needs to be connected to the local network (needs a way of entering network SSID and secure key) or host it's own network which the Pi must join.

We have examples for both module types in our Flowcode 7 Wiki.

There are also other options such as short range radio e.g. 433MHz but this probably requires more circuitry and software work at the Pi end. LoraWan is also interesting though there seems to be several flavours of this popping up. 4G and 5G is also a potential solution.

The uC would probably have to constantly monitor the sensors and then periodically communicate with the Pi to transfer the acquired data. For example the uC would constantly monitor the heart monitor ADC value and work out the BPM for you and then simply transmit this.

A LIPO battery and charging circuit are also readily available and low cost. Maybe need to think about the LIPO though as they have a potential risk of bursting into flame when charging (especially if the battery is unprotected and allowed to become damaged / bent etc) which wouldn't be ideal for a wearable. Maybe you advise to only charge when not being worn.

[Steve001]

Analogue devices have some application notes

http://www.analog.com/en/applications/m ... oring.html

May be of some use

Steve

[Steve001]

maxim also have some design notes and a demo board

https://www.maximintegrated.com/en/desi ... /6312.html

Steve

[Steve001]

More Analog Devices info

http://www.analog.com/en/applications/m ... ignId=3227

steve

[EtsDriver]

http://www.nxp.com/products/reference-d ... n:HEXIWEAR
This could be intresting for you as this one allready has heart rate sensor built in... Not programable on Flowcode unfortunately, but the NXP system is pretty easy to learn... Maybe NXP MCU range(s) come later to the Flowcode V10 ? No, seriously the K64F would be intresting to see on Flowcode!