I have a small medical device which transmits blood glucose level to my cellphone. basically just reads sensor output (NFC) and transmits to my phone using bluetooth. Every couple of days it needs to be recharged. Ages ago I ordered a spare charging cable from amazon (same cable as pebble watches and many others) USB to a small 2 pins connector with polarized magnets to hold it in place.
Yesterday I couldn't find the original cable so I just grabbed the spare, plugged it in and BAM it let the smoke out faster than old Lucas ever did. So I looking into things a bit and found that most of these cables are set up with the (+) side by the S magnet. But the original came with the (-) next to S and NO polarity protection. Incompetent engineers, I slit the device open and they easily could have found space for an extra diode. I also didn't know that a 5 v UBS charger could cause such a big spark. But WHY go to the trouble of using a semi standard plug interface with POLARITY! and then WIRE IT BACKWARDS?????
So that was the end of a $170 device that contains maybe $3 of electronics but missing a $0.01 diode.
Yesterday I couldn't find the original cable so I just grabbed the spare, plugged it in and BAM it let the smoke out faster than old Lucas ever did. So I looking into things a bit and found that most of these cables are set up with the (+) side by the S magnet. But the original came with the (-) next to S and NO polarity protection. Incompetent engineers, I slit the device open and they easily could have found space for an extra diode. I also didn't know that a 5 v UBS charger could cause such a big spark. But WHY go to the trouble of using a semi standard plug interface with POLARITY! and then WIRE IT BACKWARDS?????
So that was the end of a $170 device that contains maybe $3 of electronics but missing a $0.01 diode.