The hard part in this kind of thing is the algorithm and software development. I wonder how comprehensive his code is. Would be cool to find out.

I was assured by many engineers in the first Stages PM thread that that that is the easy part. ;-)

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Styrrell

That is seriously cool and I would love to have the smarts to do something like that, but I still think my quarq looks nicer! :-)

pretty cool, except in the end i would end up w/ a $350 pile of junk and possibly electrical burns

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M.S. x 2; CSCS; ATC/LAT, Functional Movement Specialist, USA Track and Field Level 1

Yes, the hard part is making it look neat and expensive so you can sell it.

No one would ever buy a tangled mess of wires taped to a crankset.

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Run PR's: 18:05 - 36:58 - 1:22:59 - 3:07

Wow. Engineers are SMART dudes.

I have the skills to do it but I don't have the time due to training load... oh I also already have a SRM :)

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Chicks are like Voltron, the more you can get, the better it is." -Tucker

his pictures are in the small ring. I'm unimpressed.


seriously, this dude has some talent - or at least, determination.

I was wondering if anyone else was going to pick up on that :)

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Chicks are like Voltron, the more you can get, the better it is." -Tucker

Hi, I noticed quite a bit of traffic to my blog from here and saw this discussion so figured I'd sign up and comment.

The small ring thing - There is just enough clearance to operate the prototype in the big ring, but because it's so close I haven't been doing much testing in the big ring. It's still just a prototype. I'm measuring the torque before the spider so it doesn't matter how many rings, teeth, shape, or size.

Both my drive side sensor and Stages are very similar in how they measure. My non-drive side is an ideal load cell though compared to anything out there making it highly accurate.

Thanks for your feedback!

Multiply the $350 by 2-3. Because as en EE, I know you're going to make a complete hash or literally set on fire the first attempt or two. Don't buy one of each part. Buy at least two of each. Potting/gluing/solder mistakes, etc. And as the author, you're guaranteed to have at least one short at one time or another.

why not place your circuit board into the bottom bracket? that would clean it up and allow use of the big ring.

i like what youre doing, keep it up!

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who's smarter than you're? i'm!

I tried that with my second prototype, V2, and it didn't work well as it blocks much of the wireless signals to the point where I was only getting an update once ever 3 - 4 seconds on my Garmin Edge 500 on the handle bars. I still have V2, it was shown on my blog. The antenna needs to be outside covered in a non-metal material.

Interesting...this is almost exactly how Jim Meyer (Quarq) got started...

All it takes is a bit of instrumentation knowledege and the thought "How hard could it be?" <said in the voice of Top Gear's Jeremy Clarkson> ;-)

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http://bikeblather.blogspot.com/

Welcome and thanks for signing up here! I saw your blog turn up on Hack a Day & thought this place would be quite interested in it as well so I posted it here. I'm actually quite suprised it's only had this many comments, the DIY Di2 TT shifters had several hundred and spawned a few replicas across the internet - If you're interested read here

The big ring comments are sort of an inside joke here, there's some "rules" be followed when taking pictures which you might see posters refer to, chain in the big ring, cranks at 90 degrees and valve stems upright etc. If you post pictures around here you're more likely to get people chipping in about how you've not cleaned your bike / patio / lounge than what the photo is actually about :)

Once again, thanks very much for signing up & I hope you stay around here as DIY geekery is very common here :)

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Chicks are like Voltron, the more you can get, the better it is." -Tucker

Just wanted to take the opportunity to say kudos. Really great work. Are there any barriers to using the same setup with a carbon crank?

Your videos and explanations are insanely cool. Please keep us updated on your progress.

Without shielding there may be some static electricity interference.

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who's smarter than you're? i'm!

Thanks for the support from all.

I've heard Stages mention about "hysteresis" in carbon cranks. I haven't seen it personally but there are papers on it - I'll have to see if this is fully reversed forces or unidirectional. I'd like to see if for myself before I discount the possibility. I plan on seeing if I can source a used left arm of a Sram Force or Red crank to do some testing with before discounting it. I can read well enough but I tend to subscribe to Toyota's "Genchi Genbutsu" - go and see for yourself.


Sadly, I'm guessing the barriers to setting up and building a power meter is a little more difficult for people to swallow than building up Di2 TT shifters.


The blog is updated usually once or twice a week. Right now I'm trying to get my BT 2.0 to ANT+ translator working, though it's not high on the effort list.

>It's still just a prototype.

You need to improve your attitude. It's ready for an Interbike booth and Spring official release announcement :).

Much appreciate the vote of confidence. I'm not quite sure, maybe a little more polish and work ;) Thanks

I agree! I love that there are guys like you out there to keep me thinking and on my toes! please keep us all updated!

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H*
Dream. Dig deep. Execute. Smile.

One of the big questions driving behind my project has been determining if there is a market for L/R measuring power meters. A friend of mine has been suggesting a "Kickstarter" Campaign to raise funding to accelerate development and convert my prototype to a more commercial product. Considering how large this forum is I'd love to hear some feedback on if people think this would be a good idea.

Thoughts? And thank you all in advance.

I've got a spare Rival crank coming in the mail soon. I might just have to have a go at this.

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Jordan Oroshiba --- Roadie invading Triathlete space for knowledge access

I'm definitely bookmarking this page and your site. I might have my power meter by the end of the year after all!

Great work!

And also, your seat is too high.

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__________________________________________________
Hunter Robinson
http://www.twitter.com/el_slice
http://www.elslicerideco.com
Sponsored by: http://www.92fifty.com

Just posted an update comparing my prototype to a new Powertap G3.

After recalibrating you'd be hard pressed to see a difference. Some other things of note, such that a Powertap only updates at 0.8hz instead of the 4.06hz it's capable of!

http://keithhack.blogspot.ca/...ersus-prototype.html

Just wanted to post back to this as a update.

I've currently been working with the new Nordic Semiconductor Arm microcontroller which has a built in ANT+ transceiver. It's a very low cost chip that has allowed me to do a major design change. The board is quit small and unobtrusive and the developer kit version is < 5ma current draw equating to 100+ hours per coin cell battery (CR2450).

Once the antenna is trimmed and tuned the board will be 27 x 32 mm sitting between the right crank arm and the chain ring. For those interested please take a look at the blog, and if anyone is a cyclist in Kitchener-Waterloo Ontario or surrounding area then feel free to drop me a line if you are interested in being part of the beta group. I'm on track for August prototypes for people to test.

http://keithhack.blogspot.ca/.../boards-ordered.html

Yes Toronto is certainly close enough, I'm there usually twice a month. Pm me.

I should note, currently all prototypes are going to be based on SRAM Rival GXP. They are 172.5mm crank arm length and 53/39 Cranks. There is one SRAM S950 that I'm using to test the viability of Carbon Cranks, however initially I need to stick to aluminium.

The idea is that they will be lent to people to test with for a few weeks and if there are any problems to give me a call.

Thanks

I'm in Toronto as well and would love to be part of the beta testing!

I was just in the waterloo area a few weeks ago for the Victoria's duathlons, too!

Pm incoming...

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Duathlete by choice?

Oh man I'd be interested in making this. My soldering skills are mil-spec. :)

Will you let us know when the PCB is done... with the printed-on 2.4 GHz antenna I assume?

The biggest challenge doing these things is making a decent PCB and putting it all in a form-factor appropriate case which will also accommodate the battery and the buttons/switches. Finding the parts and soldering them onto the PCB is the easy part.

Edit: oh yeah I may have access to 2.4 GHz service monitors (spectrum analyzer, receiver, signal generator, combined). I know we have 2 GHz units all over the shop. Probably at least one > 2 GHz somewhere.

The next challenge is the reflowing of the components. Two of them in particular are improbable to do by hand (The nRF51422 is a QFN and the weird BGA Balun).

I'm also converting to a two part epoxy for strain gauge installation. This is normally what's used for long life transducers (All commercial power meters use this) but it requires elevated temperature setting. So there are some challenges to replicating the new design in total and new features like fully active thermal compensation is still being developed. The short is this should almost never require re-zeroing during a ride. I'm guessing, but I suspect my approach is similar to Rotor's.

Uh oh BGA. Yeah that's an issue. It can be done by hand - reflow the PCB and then use a heat gun to attach the chip carefully without damaging it thermally. But realistically BGA etc... are designed to be assembled by robots.

Keep is informed please. This is very interesting. I've not worked with such strain gauges before. I ought to get some and experiment....

Keep me on your mailinglist please. Kitchener, a block down from Waterloo in Westmount :-) I guess I can also offer my services in software dev.

My email is in my profile, I think.

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Citizen of the world, former drunkard. Resident Traumatic Brain Injury advocate.

Dilbert,

Seriously, one lucky guy to get that nickname on anything

Also, in terms of strain gauges I've done a lot of experiments and there will be quite a few more to ensure the quality of my design. Some posts have a lot of detail, some are more superficial. So worth a read potentially if you want to get into strain gauging. I also have some youtube videos that are on the page linked back on the first page of this thread.

Thermal compensation
http://keithhack.blogspot.ca/...and-calibration.html

Force Sensitivity to offsets (and more thermal data)
http://keithhack.blogspot.ca/...testing-results.html

My old Prototype versus Powertap
http://keithhack.blogspot.ca/...ersus-prototype.html

While I wait to get my boards I'm designing the enclosure to be rapid prototyped via 3d printers. This is all consuming at this point.

I just updated my blog last night with my latest prototype tested outside with some video. It's located here

http://keithhack.blogspot.ca/...sting-video-and.html

I also provided the fit file and a link to the garmin connect site. I need to get the housing finished to secure the battery.