Originally Posted by Mullet
This was between + in from the wallwart and on + on the first battery terminal with the batteries disconnected and power on.
1.25V is expected between ADJ and OUT, not IN and OUT. The voltage drop between IN and OUT varies depending on the battery voltage, even if all else is fixed.
The data sheet for this version of the LM317 says that pin 1 is Adjust. Pin 2 is Vin and Pin 3 is Vout.
I'm not aware of any standard way to number the pins on 3-pin parts. Packages with so few pins typically have their pins function-labeled, rather than numbered.
In data sheets, such parts are usually drawn as 2D parallel projections, with no standard orientation, which makes it easy to mentally flip things around so you get the pin order backwards.
This is especially easy to do when popping back and forth between data sheets for TO-220 and TO-92 versions of the LM317, since some manufacturer data sheets draw TO-92 from the bottom view. When I see that characteristic D-shaped outline, I initially see it as from the top, probably because I'm used to seeing these parts from the top side of the board. (I made that mistake yet again while composing this message, thus the edit!)
The data sheet for this version of the LM317
What version is that? Please give manufacturer and package type, at least.
Which one is that?
The only current schematic on my site that I'm aware of with an LM317 based trickle charger is the PIMETA v2 schematic, which doesn't have numbered LM317 pins.
Again, which one? I have many parts lists on my site.
Edited by tangent - 4/9/14 at 4:23am