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?
-sam
"randomname" wrote in news: snipped-for-privacy@m79g2000cwm.googlegroups.com:
Age and heat immediately come to mind. You need to make sure you're not overheating it.
Puckropper
-- Wise is the man who attempts to answer his question before asking it. To email me directly, send a message to puckdropper (at) fastmail.fm
Presumably, you have a rectifier on there. Eh well this is SEB, one can never be too sure..
Tim
-- Deep Fryer: a very philosophical monk. Website:
Hi, Sam. Assuming you've got a 12VDC wall wart (you can check on the label), it's made to open up (no power) when it's drawing too much current.
If you're drawing more than 300mA, it's supposed to croak, and that would be my first guess. You might want to check your wiring, and get another wall wart.
Actually, it might be a good idea to make yourself a little power supply that has overcurrent protection, and use the wall wart after it's debugged and ready to go.
Sorry -- hope you can iron it out.
Good luck Chris
Well......... A battery is DC and a transformer is AC. But do you actually mean a 'transformer' or some 'wall wart' type device ?
Graham
it was 12v AC 300ma.
i guess i just tried to pull too much current from it. it was really hot when it died. i miss it.
thanks,
-sam
mean
Not DC ?
Watch out for that. It's the heat that kills them.
You may find a similar one thrown out with rubbish. There's a depot near me where they keep aside things like that if they get a chance.
Graham
On 30 Aug 2006 21:41:22 -0700 in sci.electronics.basics, "randomname" wrote,
What did you use to convert the AC to DC to match the requirements of your 555 circuit?
mean
(aside) them 555's are robust devices.
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...
Bye. Jasen
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):
| | 12VAC .----. + | o------. ,--o~ +o-----o---o |120VAC in)|( | | | | )|( | | +| | o------' '--o~ -o-. --- 15VDC out | '----' | --- | BR1 | |470uF | | |25V | '---o---o | - (created by AACircuit v1.28.6 beta 04/19/05
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.
Cheers Chris
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.