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Finished my Wearable project!

by stephanie on Mon May 28, 2012 8:51 am

This past weekend I finished up my wearable project. It started as an idea to have a digital compass and photography light-meter that would be small and light and easy to wear. It grew quite a bit from there. In the end it's a combination of Adafruit and Sparkfun goodies, wrapped in a leather package that I call the "Integrated Sensors Electronic Bracer (6)" or ISEB6 for short. The six stands for the number of sensors it has.

Image

The six sensors built into it are as follows:
  1. Illumination is measured with a TLS2561 digital luminance sensor.
  2. Magnetic fields are measured with an HMC6352 digital magnetometer.
  3. Location is detected with an MTK3339 GPS module.
  4. Humidity is measured with an HIH4030 analog sensor.
  5. Galvanic Skin Response is measured with a simple resistor divider and gold-plated electrodes inside the bracer.
  6. Local temperature is measured using the on-board temperature sensor in the ATMega32u4 microprocessor.

I have a detailed write-up on my blog: http://planetstephanie.net/2012/05/27/i ... ic-bracer/

And the sketch and my design notes can be downloaded here: http://planetstephanie.net/blog/wp-cont ... /ISEB6.zip

There's a few more pictures like this one, detailing the electronics & how it comes together:
Image

A big thanks goes to Adafruit: without everything I've learned here, and the cool goodies you sell, I'd never have been able to achieve this. Thanks very much!

Cheers!
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Re: Finished my Wearable project!

by philba on Mon May 28, 2012 10:42 am

Congrats. Looks like a good job. What kind of current draw are you seeing? I suppose the real questions is battery life... What kind of things did you do to reduce the power usage of your system?
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Re: Finished my Wearable project!

by stephanie on Mon May 28, 2012 12:51 pm

It has a few different 'modes' to help keep the current draw to a minimum. In 'active' mode, all the peripherals are running - GPS, compass, light sensor, etc. and the screen is very 'active' as seen in the images. Every second the peripherals are polled and the screen is updated. At full draw it averages 42mA and can peak at about 52mA. I believe the peak is when the GPS is in acquisition mode, where it can draw a few extra mA.

The 'sleep' mode turns off everything that has an off/sleep mode, and the screen displays only the time in HH.MM format. Updates are only done once per minute, prior to updating the screen. In this mode it draws 14mA. I have it coded to enter sleep after 15 minutes of 'inactivity' (i.e. no button presses).

There is an inbetween mode for when I have the GPS tracking, but everything else off. In this case the other peripherals are in low-power mode, the screen is in 'sleep' mode, but the GPS stays active, that runs around 36mA. This mode would be if I was using it as a 'walk tracker' (monitoring my time, speed, distance).

When chosing components, I paid close attention to what the current demands were and if the item had a low-power mode or not. Eg. the GPS uses a few microamps when asleep, ditto for the compass and light sensor. The humidity sensor on the other hand has no sleep mode but only uses about 200 uA. For the voltage divider for the battery voltage reader, I picked resistor values that would ensure a very low current, and the galvanic-skin-response was the same. Both of them are less than 100uA together.

And finally, I did a few obvious things like disabling the Pro Micro's on board LEDs. Even if they only used a few mA, it didn't make sense to leave them running - particularily the power LED which would have been lit constantly. To disable them, I desoldered their current-limiting resistors but left the LEDs in place (on the grounds that it's easier to replace the resistors if I want them again later, but more fiddly to replace the LEDs.)

So far in testing, I've yet to actually run down the power completely. The closest I got was 44 hours, at which point the LiPoly was still reading over 3.4v. Then I accidentally shorted the battery while adding the resistors for the voltage divider, and had to apply power to the charger to get the LiPo to turn back on. I'm pretty confident that it'll do 48 hours if the GPS isn't left running all day long.

Cheers!
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Re: Finished my Wearable project!

by kscharf on Tue May 29, 2012 2:44 pm

That looks like the bracelet that Turanga Leela wears in Futurama. Now I know what it was for! Nice project.
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Re: Finished my Wearable project!

by stephanie on Tue May 29, 2012 6:48 pm

Well, Leela's wrist thingy was not my original inspiration, but it actually did come to mind as my "ISEB6" progressed.

Cheers!
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Re: Finished my Wearable project!

by pdp7 on Tue May 29, 2012 9:42 pm

Very cool project! I'm curious - do you find that OLED is daylight readable?

Thanks,
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Re: Finished my Wearable project!

by stephanie on Tue May 29, 2012 10:14 pm

It can be read in bright sunlight, but it takes me a moment to 'focus in' on it. The display does appeart faint but legible, in the afternoon sunlight.
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Re: Finished my Wearable project!

by pdp7 on Tue May 29, 2012 10:29 pm

Thanks very much for the feedback on the display - I appreciate it.
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Re: Finished my Wearable project!

by johngineer on Tue May 29, 2012 11:07 pm

Very cool, Stephanie!

I have a similar project in the works as well, as a complement to my mech-eye project. Mine's not quite as sensor-equipped, however. :)

How exactly does it mount to your arm? Does it snap onto another piece? Is it tied with lanyards? The question of how I would mount my design to my arm is still up in the air for me, so I'm very curious to see how you did it.
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Re: Finished my Wearable project!

by stephanie on Wed May 30, 2012 7:10 am

Hehe, the 'closures' are something I've been struggling with for about two months, and I'm still not happy yet.

I originally tried using lace, to lace it on. Looked great, but nigh-impossible to do using just the one hand. Then I tried replacing the lace with elasticized lace, figuring it would be stretchy enough to slide on and off. The problem with that was, with the 10 or 11 holes I had originally made, there were too many 'loop's and it was too hard to stretch.

I looked at straps and buckles, eg. from leather watch-bands, but wasn't convinced it would work, or look good, or be comfortable. I considered snaps, but was concerned with maintaining a comfortable 'fit', as the snaps wouldn't have been adjustable. I have a friend who's making something similar and she's using velcro, but I didn't want that at all.

What I ended up doing, is where I had the rows of holes for lace, I trimmed off all but two pairs of holes. Then I used two small loops of elasticised lace. So it stretches open to slide it on, and there's enough tension in the loops to hold it in place without being uncomfortable.
Image

However, I'm not happy with how it looks. I'm planning to drop by my local Tandy leather shop this week to ask them for some suggestions on closures.

Cheers!
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Re: Finished my Wearable project!

by johngineer on Wed May 30, 2012 10:04 am

I like the elastic lacing idea -- I hadn't thought of that.

One thing I was planning to do this summer was visit a renaissance faire or two and consult with some of the leatherworkers who set up shop there. I figure they might have some good ideas about fastening as well.
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Re: Finished my Wearable project!

by pburgess on Thu May 31, 2012 12:26 am

Regarding closures: if you want to maintain the leather aesthetic, I'd suggest straps and buckles. The good news is that they're not that hard to do nor are the parts terribly expensive. The bad news is that the tools are OMFG expensive...but from your photos it looks like you might already have a rivet setter and at least one size of hole punch. Nice thing about Tandy, at least the one near me, is that they have a project area in the back where folks meet up on weekends to make things...and if you're buying some buckles and rivets, they might let you borrow some tools and hang around.
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Re: Finished my Wearable project!

by stephanie on Thu May 31, 2012 6:32 am

Johnengineer, if you don't want to wait for a ren faire you can find some photos of their gear online. There are at least a few businesses that supply clothes and accessories for historical re-enactors. I did find some bracer images that way.

Pburgess - you're right, I do have some leatherworking tools already. I don't have a rivet setter though - I've used screw-rivets for this so I can completely disassemble it as required.

I do want to try using straps and buckles, if I can manage to keep them comfortable. Tandy has a 'wristwatch' kit that I'm going to look into, it basicaly has the small straps and little buckles matched up, so if I can just bolt those to the bracer it might do the trick.

I'd actually like to improve the entire aesthetic over-all - this is basically the 'version 1', it works but it does not look great. So I will probably re-do the outer leather 'panels' and try and dress them up a bit.

Cheers!
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Re: Finished my Wearable project!

by pburgess on Thu May 31, 2012 2:20 pm

Oh! I'd thought watch straps would be too delicate...but I see the kit you're talking about, not bad. And having everything pre-punched is really handy.
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Re: Finished my Wearable project!

by Skewworks on Tue Jun 05, 2012 2:35 pm

Stephanie,

You're project is great! And I wanted to thank you for inspiring me.

I've been working on a Pipboy project for my fiance using a 4.3" touch screen LCD, but after seeing your build we've decided to change it all around and be more like yours. We're removing the 4.3" and swapping it for a 128x128 color OLED that we already had laying around as well as the same Adafruit GPS & a 4x3 keypad. Hoping to have it ready for her before we go on vacation in 2 weeks.

Your LED flashlight at the end is brilliant, very Pipboy-esque! I will definitely be stealing that idea for my own build.

Congratulations and thanks again for the inspiration!

BTW, I wrote a full featured driver for that GPS in C# as well as a method for plotting the point on a screen capture of Google Maps to show the location on the screen, if you want to port it over to Arduino for your own use you can find it here: http://skewworks.com/products/MTK3339%20GPS%20Driver
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