eddy current bike light?
eddy current bike light?
(OP)
A couple of guys in Holland or Germany created the Magnic Bike Light.
http://urbanvelo.org/magnic-light/
I understand eddy currents, but am skeptical that the amount of power available is enough to drive the LED. They claim no moving parts other than the rim of the bike wheel.
http://urbanvelo.org/magnic-light/
I understand eddy currents, but am skeptical that the amount of power available is enough to drive the LED. They claim no moving parts other than the rim of the bike wheel.





RE: eddy current bike light?
RE: eddy current bike light?
To me it looks more like an eddy current type absorber used in dynamometers, except backwards so it works as a generator. Ergo, permanent magnets in the light impart a magnetic field into the conductive rim. When the rim passes through the field, eddy currents are generated to oppose the change in magnetic field (Lenz's law), creating an attractive force and slowing the rim. In a dynamometer you energise the magnet with a coil to change that attractive force, so I guess in this design the force drives the coil instead, giving you electrical energy.
RE: eddy current bike light?
RE: eddy current bike light?
Keith Cress
kcress - http://www.flaminsystems.com
RE: eddy current bike light?
RE: eddy current bike light?
Until you had to change a tire, and popped 7 or 8 of the stupid little magnets off the rim whilst prying on the tire bead. Or had to wipe/scrape the iron filings and Fe(2) oxides off the magnets once a week...
RE: eddy current bike light?
And although they do highlight that it is "frictionless", that does not mean there is no energy transferred, there is. The magnets acting on the rims to capture energy from eddy currents is indeed going to be imparting a retarding force on the rim, just like the Eddy Current Brake system. I could feel it on mine. What makes it viable now is the high energy to lumen ratio of the LEDs because it would keep the effort from the peddler low. I would consider also coupling it with a slow discharge cap so that at least it could stay illuminated for a minute of so when at a stop light.
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RE: eddy current bike light?
Um, perhaps, did you mean high lumen to energy ratio?
RE: eddy current bike light?
Low energy, high lumens.
Another brain fart...
"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: eddy current bike light?