[clug] Exercise and pay the bills!

Paul Wayper paulway at mabula.net
Sat Feb 7 20:45:56 GMT 2009


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Hi all,

I had an idea a couple of days ago that I'd like to explore with some hardware
and electrical engineering types.  I'm hoping to find them on this list :-)

Most exercise machines sold these days just use either friction, magnetic
coupling or resistive loads as the 'sink' for work done.  Since Kate and I are
in the process of getting a solar panel system put in, and the inverter can
take 48VDC and put it onto the grid as 240VAC, I was thinking of getting a
48VDC generator and hooking it up to some exercise system and generating
actual usable power while I work out.

This is where my understanding of electrical generation starts getting me
unstuck.  Most exercise systems have a display that tells you how much power
you've used and various statistics on it - OK, so we need a little
microprocessor - and also allow you to vary the load so your work varies over
time.  I can see I'm going to have to learn a bit more about microprocessors
for the first part, but I'm not sure how to execute the second part.  Multiple
small generators that get switched between short circuit and output to the
inverter?  Some kind of DC/DC converter with a variable duty cycle?  (Yes, of
course, I can have gears, but that makes the device a lot more cumbersome and
I'd like to avoid that).

Any thoughts?

Have fun,

Paul
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