Sciencemadness Discussion Board

remagnetize a demagnetized magnetic stir bar

rockyit98 - 26-11-2020 at 07:28

i was making 98% H2SO4 and i forgot one of my magnetic stir bars in the vasal. so it got hotter than rated 250C and became a dud. even before that it was getting weaker by repeated use.

then I remembered watching a "how it's made" episode where they showed how magnets are made.in it by pulsing the pre magnetize "magnet" with a strong magnetic field it becomes a magnets. it's due to a process called " Magnetic hysteresis ".with this knowledge i made a simple yet effective way to remagnetize such stir bar.

WARNING- RISK OF ELECTRIC SHOCK
do this away from sensitive electronics
repeat at your own risk
using magnet wire i wound a coil with a bobbin that match the stir bar so it will side right in easy. about 100 turns (i forgot to count :D)
i used 330uF 400V Electrolytic capacitor (mind the polarity ) charged up to 325V using AC mains by using full bridge rectifier and a incandescent light bulb. after charging the capacitor while being careful I removed it.
after i inserted the stir bar inside i fix it at the center and parallel with the coil with a dab of hot glue. after it's secured in place i shorten the capacitors terminals with the coil. with that tiny sparks flew and it was done.it was better than new!
NOTE : important
remember to strip the enamel at the tips of the magnet wire
use rubber gloves and eye protection , double check polarity otherwise capacitor will explode, use rated 400V or higher capacitor


cap.jpg - 101kB coil2 .jpg - 189kB cap2.jpg - 162kB fbr..jpg - 138kB CHARGING.jpg - 31kB discharging.jpg - 19kB coil.jpg - 278kB