When starting a new project, RTFM first!

How do you turn this

mag trainer

into this?

Computrainer

Short answer is you don't, you order a Computrainer from Racermate, they charge you around $1600 and then you sell the old one on Craig's List.

Long answer is you don't, but I think you can get some of the same features by automating the old mag trainer. Equipment list is:

• Arduino with USB or XBee communication to a PC for data logging/display
• Reed switch speed and cadence pickups, suitably debounced
• Polar receiver from Sparkfun
• Stepper motor and stepper motor driver, also from Sparkfun
• Some hardware, especially to adapt the stepper motor to the mag trainer resistance adjustment cable
• Software for the PC (some coding required)

Goals are:

• Estimate average and instantaneous power output, based on trainer documentation
• Graph power vs crank position
• Automated resistance adjustment for training sessions
• Record HR, speed, cadence, power results for session
• I'll pass on all the fancy graphics (other riders, etc) and dead accurate power values - the homebrew solution should at least be consistent, give me some better training feedback, and cost under $200 (my development time not included. Could be packaged and sold I guess, but at least for now that's not the main goal.

The stepper motor and driver are the big question marks for me - I've never used either before, and I'm not sure how much force I'll need to pull the resistance cable - so I decided to start there. And promptly released the driver board's magic smoke. I pulled a wire from the motor driver output side while the motor was powered and fried the driver chip. Had I read the warning on the web page (not even buried at the back of the datasheet!) I would have known better 

Note: Do not connect or disconnect a motor while the driver is energized. This will cause permanent damage to the A3967 IC.

How many times have I told students "DO NOT MESS WITH THE WIRING WITHOUT REMOVING POWER!"? At least I have another example of why you need to do that.

So, development of the resistance adjustment is stalled while I wait for a new driver board. Guess I have to start with the speed/cadence and heart rate side first.

RTFM, RTFM, RTFM....

Rebooting another blog

It's not that I haven't been making stuff. I just haven't been making a lot of my own robots lately. This is mostly due to being involved with FIRST, and specifically getting the FTC (FIRST Tech Challenge) middle school pilot program started with FIRST in Michigan. Very worthwhile programs and rewarding when you see the next generation of engineers start to get excited about problem solving and making stuff, but it can take over all your available time. And some that isn't really available, so you end up getting behind in other projects. Like sleep.

But now that I've pretty much passed FTC on to the next generation of coaches and mentors, I'll be getting back to my own maker projects and other interests like mountain bike racing. My upcoming projects live at the intersection of bikes and tech - turning my dumb indoor trainer into a computer controlled bicycle dyno, building a chain break in rig and using paraffin as chain lube, and developing a data acquisition system for mountain bike suspension tuning.

And I've started home brewing beer, so there will be some mention of that I'm sure. Not just brewing and tasting, but also developing recipes and building some equipment like wort chillers, all-grain brewing system, and kegging.

Other possible projects include some FTC training materials (you have to go into witness protection to get completely out of FIRST I think), PowerWheels racing at Detroit Maker Fair, working on an I2C bus motor controller using Digispark, quadcopters, and learning to use the Freescale Freedom board and K40 Tower system.

Some of this may end up on Instructables, some may get turned into open source projects, some may actually become products. This blog will be my live engineering notebook, so all the dead ends, discoveries, missed deadlines, abandoned ideas, unexpectedly easy successes and surprisingly hard tasks will be visible.

If you want to follow my bike racing adventures, check out CatVI. For more on FTC, check out FTC Coaches Corner.