Problem using LM317T

[TigerhawkT3]

I'm trying to use an LM317T with a 25Ω rheostat (plus a 1Ω resistor) to make a fully variable driver for series LED strings (my current setup is 3x12V SLAs and 9xQ2). From what I've read, it shouldn't be that complicated, but it's not doing what it should. As you know, the LM317T has three pins: In, Adjust, and Out. I've got batt+ connected to In, my rheostat+resistor connected between Adjust and Out, and I've tried connecting my LED+ to Ajust and Out with the same results. The problem is that no matter what resistance I set with the rheostat, I only get 11.8mA of output. When LED+ was connected to Out, the high end of the rheostat gave me 11.9mA instead of 11.8. I'm completely stumped. Can anyone tell me what I'm doing wrong?

 

[Mr Happy]

You will want to connect up your LM317 as a current regulator. See this article for an illustration. The "R" in the circuit diagram shown there is what you will want to vary to adjust the current (and thus brightness of the LEDs).

 

[TigerhawkT3]

I had done exactly that...

...Or at least, I thought I had.

It turns out that the schematic diagrams all over the web show In, Adjust, Out from left to right. I don't know why. I stupidly used that orientation instead of going with the pictures of the actual LM317T (which show the actual pins labeled Adjust, Out, In, from left to right).

So, the lesson here is that the schematics make it LOOK like it's In, Adjust, Out, but it's really Adjust, Out, In. Jeez.

P.S.: Now that it works, I have a 9xQ2 floody spotlight adjustable between 40mA and 1.2A, or an 11xQ2 floody spotlight adjustable between 40mA and 300mA.