USB to Travel Clock Circuit Help :)

I've got this little black Oregon Scientific travel clock thing with a transparent screen. It was an old gadget of grandma's I found years ago. I was eying it, and I had a damn good idea for an Instructable-worthy project. I'd eventually like to run this off of USB power. Currently it has a little button-battery in it (Energizer 357, bout 1CM in diameter). I know USB out is an unsteady 5V, so I'd need a capacitor to regulate the current, I guess, and the necessary circuitry to adjust the voltage to whatever this little clock runs on. Any advice for such a novice?

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Brennn1010 years ago
I don't know, just a thought, maybe instead of a capacitor, you could use a voltage regulator to output 5 Volts.
Goodhart Brennn1010 years ago
to use, say a 7805 (5 v regulator) you need a power supply voltage that can be unreglated DC 8-18V but it can not drop below the 8 v minimum and continue to function.
Patrik Goodhart10 years ago
You could, however, use a variable voltage regulator like an LM317, to get any voltage between 1.25 - 2V, from a 5V input voltage. Probably overkill. Then again, I don't know how noisy a USB power supply is, or how sensitive a clock circuit would be to those fluctuations.
guyfrom7up10 years ago
A simple voltage divider might work. Find the current taken by the battery.
mikesty (author)  guyfrom7up10 years ago
The battery is dead, and I'm not really sure how to measure the draw from the clock. I do indeed have a multimeter,
NachoMahma10 years ago
. FWIW, that's a 1.55V silver oxide battery
mikesty (author)  NachoMahma10 years ago
Thanks, that helps!
Well, obviously you need the help of some people more experienced with such things. I'd try a community like that on, and I-- Oh, nevermind, you found us already.