In article ,
David Nebenzahl wrote:

On 3/14/2010 9:01 PM isw spake thus:

In article ,
David Nebenzahl wrote:

To bring this little saga to a close, I built a little AC adapter for my
Fuji Finepix digicam: brought in 5 volts from a little Samsung wall
wart, put the regulator and an electrolytic cap in a film can on a
little piece of perfboard, and brought the power out to a 2.5mm power
mini jack.

The long and short of it is, the camera doesn't work on this supply. It
puts out 3.25 volts alright, even when plugged into the camera, but the
camera just sits there and does nothing. My suspicion is that the power
jack is just not quite the right size to make contact (or else there's
something screwed up inside the camera that makes it not accept external
power, which seems unlikely).

What kind of regulator are you using? A lot of regulators will not
function properly with only 1.75 volts across them. It might be failing
only when the camera wants more then average current -- like when it's
trying to focus.

It's an NTE 1904 (replacement for ECG1904). Similar to the LM78xx
series, I guess; just your standard 3-terminal positive regulator.

According to the data sheet, it's *not* similar to a LM78xx because it
does have a low differential requirement -- 0.45V.


Not sure what you mean by only 1.75 volts across; do you mean the
difference between input and output?

Yes. Some regulators (LM78xx for example), need more like 2.5V to work
properly.

In any case, I assume it's working
correctly, since I can see 3.xx volts at the output.

You do happen to be using a low-dropout device, but still, you have to
measure the voltage under maximum expected load, not open circuit, to
really see whether it'll work.

I tried it using a variable DC power supply; no better result. I'm
thinking there's something wrong with the camera.

(And by not working I mean the camera doesn't respond to the power
switch *at all*. No little beeps, no display, nothing.)

Does it work if you stick the proper batteries in it?

Isaac