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I am looking for a solution regarding the gsr, accelerometer, heart rate, skin temperature. From this other question seems that Grove isn't clear enough with their documentation. So I am looking for other ideas. I already know cooking hacks and I am afraid that with their hardware I can't make my Arduino wearable and comfortable enough, because at the end I'd like to attach a lithium battery with a case (that's why I don't want the extra bulk of a shield).

More details of what I am looking for.

Accelerometer: Range: +/- 1.0g Minimum resolution: 0.01g

Galvanic Skin Response Range: 56k Ohms to 20M Ohms Two-standard-deviation error of +/- 4.0% otherwise

Skin Temperature Range: 20.0°C to 40.0°C Resolution: 0.05°C Error: +/- 0.8°C

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  • Shield are just for lazy people :-). Also, stacking shield will lead to problems a lot of time. Use regular breakouts and wire them yourself to the appropriate arduino pins. You can move them around, till you have the best fit for your enclosure. – Gerben Dec 18 '15 at 19:55
  • "tacking shield will lead to problems a lot of time" Why? "Use regular breakouts and wire them yourself to the appropriate arduino pins." I'm totally new in this field and what I know at the moment is that I have to see which kind of wire goes in which kind of holes. These things are typically written with letter and numbers (on the board), right? – Gabriele Giordano Dec 19 '15 at 15:23
  • Sorry, I meant to say 'shields' not 'shield'. A lot of times different shields use the same pins, leading to problems. This forum is full of those cases. As to which connection on the breakout, goes to which pin on the arduino; sometimes it doesn't matter which arduino pin. Sometimes it has to be a specific pin (e.g. SPI or I2C pins). That's the advantage of shield. They've already done this for you. You however miss the flexibility using different pins, when required. – Gerben Dec 20 '15 at 16:06
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The accelerometer may be pretty easy (since it may not need to be in close contact with the person), but the GSR and skin temperature will need to be touching the person to work.

The first thing you will want to do is to identify the sensors that you want to use, and then come up with some ideas for how to make them wearable so that you can measure the parameters that you're looking for. Will you be able to attach them with straps, or does the attachment need to be more subtle or more comfortable? Small breakout boards are handy, but they may make the sensor uncomfortable to wear.

I'd suggest taking at look at the Adafruit site for some ideas on wearables and sensor interfacing. There is a lot of useful information there and much of it focuses on Arduino based designs. For the most part the sensors they sell and use are well documented either with data sheets or code (or both).

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  • Do you advice specific tutorials? – Gabriele Giordano Dec 19 '15 at 15:26
  • Then on adafruit there is only one sensor :( – Gabriele Giordano Dec 20 '15 at 14:03
  • What you'll want to do is figure out which sensors you want to use. Some will interface with a voltage that is proportional to the value being sensed. Those are easy, you just connect those to one of the analog pins. In most cases you could just change the pin being used if there is a conflict. There are also devices that use an interface like 1-Wire that permit multiple devices on a single pin. It will help a lot of you can say more about your project and sensors that you are interested in using. – dlu Dec 21 '15 at 23:15
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I ran into a similar quandary when making a prototype for a device that needed real test-data from an external, glove-worn accelerometer. I wound up running the data/power/etc pins from my Arduino board to a female RJ-45 jack (I've used a telephone jack on another project where only 4 wires were needed). Then I cut an old cat-5 network cable in half and soldered the wire-ends to data/power/etc pins on my external sensor board. This allowed me to separate one component's wiring scheme from the other's. (FYI: longer lengths of cable between components does increase the risk of noise/interference corrupting digital signals. This can usually be resolved by reducing data rates or by adding a few resistors/capacitors to filter the signal, but I have limited knowledge on this)

Even if you don't have any old RJ45 cables/jacks laying around, it can really help to find some way to "modularize" the various pieces that will be working together when your device is complete. If you're familiar with object oriented programming, think of it as "designing an interface" for each component. Then, even if you completely redesign the wiring for a particular component, you only need to ensure that your "interface" (aka connection) is the same, and you wont need to resolder anything on the other end of the line.

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For accelerometer sensing I used LIS3DH from STMicroelectronics, its low power(down to 2uA), small (LGA package 3x3x1 mm) and has cool build-in features (like orientation, tap and doble tap detection among other things). http://www.st.com/web/catalog/sense_power/FM89/SC444/PF250725?icmp=pf250725_pron_pr_feb2014 and there are a lot of libraries like https://github.com/adafruit/Adafruit_LIS3DH

For intro to GSR check this project http://cwwang.com/2008/04/13/gsr-reader/ Pretty easy ;) More advanced design will require a signal generator and an instrumentation amplifier. An example of such design can be found here https://www.maximintegrated.com/en/design/reference-design-center/system-board/6147.html/tb_tab1 Another interesting project is the truth wristband http://produceconsumerobot.com/truth/

The temperature part can be done with a thermistor (IC temperature sensors do not compliant with your resolution spec) and a bridge circuit. For reference check this sensor http://www.digikey.com/product-detail/en/PR103J2/615-1069-ND/2651611 and also some literature about Wheatstone Bridge http://www.ametherm.com/thermistor/ntc-thermistors-temperature-measurement-with-wheatstone-bridge

Hope be helpful.

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