Eddy current brake failure :(

A project log for Braker One Robot

3D printed single motor robot

rand3289rand3289 06/29/2020 at 00:200 Comments

I've made the eddy current brake.  It  has about 14 m of 20 AWG magnet wire wound about a chain link.  It has about 0.5 ohm resistance.

I tested it by holding the disk spinning at about 450 rpm in the slot of the chain link.  The magnet was in my hand.  I briefly applied about 10 V from a 30 A variable power supply.  I felt NO FORCE during the time the coil was energized.  It got warm within seconds so there was a lot of current ( my calculations tell me about 20 A) flowing through the coil.  At this point I call my eddy current brake a failed experiment.  It could be the magnet, it could be the low RPM or the thin aluminum plate. 

Rumbling and whining:
This thing was hard to make and it didn't work.  I had to buy magnet wire on line, drive to buy a chain in the store, drive to the beach to get sand for annealing process.  I've spent about 40 minutes heating the chain in the sand with a propane torch which after all probably didn't change the magnetic properties of the metal much but made it a lot softer to cut and bend.  I had to unspool the wire to a larger spool so I can measure how much wire I will be winding which took about an hour.  Hours of research on winding magnets, trying to figure out wire resistance, max currents, weight and other crap.  Then I had to wind the coil which took me about two hours.  I didn't want to connect it to the power supply directly since it had such a low resistance so I had to wire some resistors in parallel to lower the overall resistance because I didn't have any low ohm resistors.  Wire the coil with resistors and a switch in series.  Connect it to the power supply.  At this point I think my meter died because I tried measuring current through the low current connector.  My 30 A power supply's current indicator also died! After all that work I get no force whatsoever from the brake.  At this point I think I need to take a chill pill called fu*kitall and move on to a different type of brake.