i took a 12v 300ma transformer (meant for a little submersible pump) and cut the wire and stripped it. then i used it as a power supply for a simply 555 circuit with about 10 LEDs strobing... for some reason they were strobing a lot faster than with the 6v batteries id been using, so i start switching resistor values.
eventually, the transformer just died.
why did this happen? whats different from a transformer and a battery?
yup, the reason being that the 555 was seeing backwards voltage some of the time... the 555 wants DC, you'd need a rectifier and a big capacitor to smooth out the humps to get that from 12V DC. this setup will typically produce about 16V...
Hi, Sam. So, your wall wart was 12VAC, not DC. I'm kind of shocked it worked at all. Of course, you were using the wall wart for a small pump motor -- that would have been AC. My bad, I should have caught that. And when the AC was reverse-biased, you probably had really high current through your circuit. ICs aren't made to be powered up bass-ackwards.
If you want to drive your 555 circuit with an AC wall wart, you'll have to do something like this (view in fixed font or M$ Notepad):
If you get a bridge rectifier and a largish cap from Radio Shack, you can have this working well quickly.
And by the way, don't feel bad for the wall wart. Most of them just get thrown out in the trash when their gadget dies or the owner gets tired of it. Yours not only did its job, but it died to serve you. That's how they're designed. Just give it an honorable burial.