Current limit potentiometer problems

[niflheimer]

Hello. I've built a simple PSU based on the two regulator design - with a L78S12 in current limit configuration and a low dropout , 3 amp CS5203 for voltage regulation . It works quite well , but the trimpot I'm using for current limiting heats up a lot.

Is there any way to reduce the current through it ? At anything over 150mA it heats up a lot (as it should actually  )

I don't have any simple opamps at hand - the only ones I have are some dual ones which need a two rail supply.  And I'm out of quality wirewound pots as well  . I do have a lot of triacs , mosfets and transistors

Thank you!

Edit - forgot to add the schematic

[Skimask]

http://www.eevblog.com/2010/08/01/eevblog-102-diy-constant-current-dummy-load-for-power-supply-and-battery-testing/

Replace to pot with this circuit maybe?

[don.r]

Have the wiper of the pot drive the base of a NPN power transistor with the collector connected to the regulator's output and the emitter to the far side of the pot. Add a further resistor between the output and the pot to lower the current flowing through it.

[niflheimer]

Ty don.r , will try it tonight - I wasn't sure if it would work when I thought about doing it this way .

@skimask - I plan on doing a CC load after Dave's design , but at the moment I don't have the parts at hand - and I'm too lazy to drive 10 km to the nearest part store

I'm using this supply to test a box of assorted laser diodes I got for free - and some of the DPSS ones pull up to an amp