Monday, July 29, 2013

Status on V4.1 Accuity, Crowd Funding Comments


I wanted to give a quick update as I’m going to be away from this project for about 1 – 2 weeks. In the meantime I started a discussion on crowd funding over at slowtwitch here. Feel free to swing over and leave a comment, or drop me a line (here) as an alternative or in the comments below. I want to know peoples issues, concerns, hopes, etc. Do they see a market? is price the major issue? Is the app scene pushing adoption? Would you use a power meter if it was cheaper? Anything else?

I was hoping to get the board on the crank set and bring it with me so I could continue coding and sorting out bugs but that proved improbable. From the above photograph You can see my custom board connected to a breadboard. This is just a quick way of changing setups during testing. The board is wired to a coin cell battery that I’ve actually been using for a couple of weeks. Even after shorting it out a few times I still haven’t had to replace it. Still reads about 2.9V. Bodes well for long operation. I’m aiming for a minimum of 100 hours, hoping for 150 – 200 hours with some optimization.


From the breadboard the inputs are wired to my former V3 power meter. V3 was “sacrificed” so I wouldn’t waste a crank (makes for an additional prototype as well) and it serves as a quicker test setup than building a new one from scratch. The interesting thing Is I have a a total of 5 different ways to measure the left legs torque, and 1 way of measuring the right leg. This is great for torque testing and confirming the shear gauge measurements against other designs. I’m well past this stage, but more confirmation results certainly help the process.


Just a close up shot showing off how I’ve modified V3. The setups now connect to bondable terminals for stranded wire connections. The board will migrate onto the crank arm by the chaining and these wires will be shortened.

Look for further updates in about 2 weeks. Feel free to email me in the meantime.


  1. I don't know what the possibilities are for this project in terms of cost per unit, but if you can make these affordable you will get lots of crowd funding both from people who want an affordable power meter, and those who like to support cool projects.

    1. I did a post called Good, Cheap, Fast - Pick two here:

      This post gave a potential breakdown of costs, however there is still some leeway and the numbers are being continously evaluated and improved. Sadly, due to the labour cost involved it's hard to get a full crank below 700 based on current cost setup. I'm looking at finding ways to improve this before I look to crowd funding.

      Obviously the cheapest is to completely outsource the instrumentation and construction to Chinese manufactures. The only way to safely do this is to have someone on the ground in China to oversee QA and I can't do that. This drives up cost a little over the lowest possible numbers.

      With Powertap lowering prices I'm trying to find ways to make it even more competitive.

  2. Hi I like to be a beta tester and buy one! please send by mail the info!!!!! :)