Thinking of starting a new project...

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Thinking of starting a new project...

Postby noobSkier » Tue Feb 12, 2019 3:00 pm

For a few years I've been thinking of different ways to to get digital feedback from my skiing. Im considering building a system of force sensors between the ski boot and bindings. Maybe to start, just one force sensor under the toe lugs, and perhaps add a second one at the heels for fore-aft analysis. There seem to be some off-the-shelf components that would do the job in a small form factor. It might be useful to see your weight distribution throughout the arc, effect of different alignments, push performance etc. It could even hook up to your phone to get a graphical representation of the arcs, or even just average values/scores. Does this sound useful, or a total waste of time? Ideas welcome!
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Re: Thinking of starting a new project...

Postby Max_501 » Tue Feb 12, 2019 3:21 pm



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Re: Thinking of starting a new project...

Postby noobSkier » Tue Feb 12, 2019 3:35 pm

Cool! Thanks for sharing! Ill have to look at these products a bit more in-depth, has anyone tried these? The carv seems close to what I'm looking for.
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Re: Thinking of starting a new project...

Postby ErikCO » Tue Feb 12, 2019 7:23 pm

From the standpoint of making your own, how well versed are you in embedded systems? Programming them has gotten much easier over the last 10-15 years, but communicating with external sensors will probably end up requiring a fair amount of reading data sheets. Then you have storage, polling rate, PC connectivity, data visualization, and that is even before you start looking at how the data and PMTS go together. I've thought about doing the same project, but have just enough background to come away feeling overwhelmed.
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Re: Thinking of starting a new project...

Postby bmoose21 » Tue Feb 12, 2019 8:01 pm

I've done a little experimentation with this, using a rfduino and a couple of force sensors. You can send the data to a phone easily too using bluetooth. This stuff is not hard to protoype nowadays if you have some programming background. I think something much better than the Carv could be built, based on PMTS movements. You could in real time measure CA and CB by having a small device on the belt buckle and on the boots. Send to a phone, then bluetooth to your helmet. Force sensors on both sides of the ankles in the boot. Also angles of ski to snow can be measured. Maybe we could license the PMTS system for this device and make millions! Oh wait this is skiing, maybe just thousands.
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Re: Thinking of starting a new project...

Postby bmoose21 » Tue Feb 12, 2019 8:12 pm

Also from what I've read the instruction that Carv gives is not good. No surprise there. Love the 'carving' in the above ad. The thing is called Carv and the skiers in the ad are not carving. Maybe they are supposed to represent the skiers who are most in need of the device?
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Re: Thinking of starting a new project...

Postby noobSkier » Tue Feb 12, 2019 8:35 pm

I used to build data collection systems for commercial clients and scientific applications before I started my business. Wrote a few android apps for enterprise, no iOS experience unfortunately...but I could probably pick it up pretty quickly. From a programming standpoint, it's pretty simple to get the hardware up and running...quality phone application would take longer.

Carv is a bit intrusive with the force sensor in a footbed, so I don't see myself using it for that reason alone. I also don't trust their algorithms, like how are they determining rotation and turn symmetry? For me, angles wouldn't be that useful, and I don't see how that could be accurate. My idea is to use it primarily to make sure I'm weighing the outside ski, keeping the inside ski light, and making sure forces are symmetrical from turn to turn. You could easily write an algorithm to infer arc beginning/end from sensor data. I see that Carv is averaging everything out...would be cool to look at individual arcs too.
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Re: Thinking of starting a new project...

Postby Max_501 » Wed Feb 13, 2019 7:45 am

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Re: Thinking of starting a new project...

Postby Obrules15 » Wed Feb 13, 2019 8:34 am

noobSkier wrote:I used to build data collection systems for commercial clients and scientific applications before I started my business. Wrote a few android apps for enterprise, no iOS experience unfortunately...but I could probably pick it up pretty quickly. From a programming standpoint, it's pretty simple to get the hardware up and running...quality phone application would take longer.

Carv is a bit intrusive with the force sensor in a footbed, so I don't see myself using it for that reason alone. I also don't trust their algorithms, like how are they determining rotation and turn symmetry? For me, angles wouldn't be that useful, and I don't see how that could be accurate. My idea is to use it primarily to make sure I'm weighing the outside ski, keeping the inside ski light, and making sure forces are symmetrical from turn to turn. You could easily write an algorithm to infer arc beginning/end from sensor data. I see that Carv is averaging everything out...would be cool to look at individual arcs too.


I own the carv but haven't used it yet. It can go under your liner but it's still too thick and takes up too much space in the boot. Also there is a thick wire (similar to hotronics) that runs across the middle of the footbed which will definitely screw up balance. I've been thinking about planing down my Zeppa boards but am concerned with their durability and replacability.

I thought that Carv provided enough raw data that one could skip the on mountain trainer and look at the data after the fact. I was hoping to use it in place of video because that is extremely difficult for me to get. (I know it's not as good as video but there are things that I'm working on that might show up).
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Re: Thinking of starting a new project...

Postby Max_501 » Wed Feb 13, 2019 8:37 am

An in the boot sensor won't be a substitute for video.
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Re: Thinking of starting a new project...

Postby Jeet » Wed Feb 13, 2019 8:50 am

Me and few guys have started something similar. Video below. Old vid of Will skiing (hope he does not mind using this sample)

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Re: Thinking of starting a new project...

Postby noobSkier » Wed Feb 13, 2019 12:18 pm

This is awesome, pretty nice brushed carves too! Is that MatLab? If it's not confidential, what sensors and are you using? Do they each have a microcontroller or do they connect to a main board?
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Re: Thinking of starting a new project...

Postby noobSkier » Wed Feb 13, 2019 1:55 pm

It would be interesting to hear from coaches like Max_501 what they personally would find useful.
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Re: Thinking of starting a new project...

Postby ErikCO » Wed Feb 13, 2019 10:42 pm

Sounds like you definitely have the background for it. I have hung out in hobby electronics forums for a good many years (back in the time when the 16F84A was considered hot stuff!) and have seen all too many folks who have experience in general PC programming assume that embedded is exactly the same and then get discourage when they run into problems of things like shared timer resources or interrupt conflicts between libraries they find online!

On a different note, I would think that ideally you would be interested in both footbed sensors as well as sensors in the front/back of the cuff and on the sides of the boot, both front and back, as well as an angle sensor on each boot. Idea being that footbed sensors will only tell part of the story on fore/aft balance since cuff angle plays some part as well. Sensors on the medial/lateral sides of the foot/boot in both the front and the back would be helpful for seeing if there is a torque being applied to the boot and where it is coming from. Angle sensing would probably be the least useful but would give feedback on whether tipping is being led by the free or stance foot. The real trick would then be to stick the sensors on some good PMTS skiers, record data, then throw them out of alignment in various ways and get yet more data. Whether any of the data would be useful either for coaching or for alignment issues would be hard to guess, though. I'm sure with the correct array of sensors it would be, eventually.

I actually wouldn't think that wiring would be all that hard as most sensors are low current and low voltage so could use fairly thin ribbon-type cables. I have no idea about the size of the actual sensors, though. If they were much thicker than a coin or had any sharp edges, I would think you would have a hard time fitting it into many boots (I know you would with mine!)
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Re: Thinking of starting a new project...

Postby noobSkier » Thu Feb 14, 2019 6:52 am

Great ideas ErikCO. Sensors at the cuff makes sense, and I could see how knowing the angle of your free ski relative to the stance stance ski would be useful. Definitely adds a layer of complexity though. If I was to do this I think I'd start with force sensors between the boot and binding rather than inside the footbed...these do tend to evolve though as you go along. The force sensors I'm looking at are 1in in diameter and can be configured for 1000lbs of force.

All this would ever be is an open source indie project for the community that one could easily build themselves.
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