What kind of pots to use with LM317T?

[dwango]

I built the small circuit on the back of the RadioShack LM317T box (with a 5k pot). It all works, except the pot increases too quickly and stays at 10.39 volts for half of the distance that it turns. Do I need a different kind of pot?

[Mord-Sith]

LoL you dont even want to know what I thought you were asking at first :D

did you use an audio taper pot because you want to use linear taper. You might also try changing r1 as shown in this picture



pick (http://casemods.pointofnoreturn.org/vregtut/tutorial-1.html)

Most instructions say to use a 220 ohm or similar resistor but I think for that large of pot you want closer to 1k

[Hoot]

I've found that a 2k pot generally suffices for voltages in the range of 0 to 12V. You will never get full input voltage at the output because of the internal workings of the three terminal regulator, so you will never get the fan up to full speed, should you need to. At that point you want to jumper around the regulator circuit with a switch. Finding a 2k pot is more difficult than a 5k pot, but you can change the 5k pot to 2.5k by simply soldering a fixed 5k resistor across the end lugs. You definitely want to use a linear taper pot as opposed to an audio taper. Here's a rough graphic for changing a 5k pot to 2.5k

Hoot

[Mord-Sith]

good idea hoot ill have to remember that trick