How abt my idea of using a dual pot??

I've build a supply very much like the one you're building, a single turn is plenty fine resolution in my experience. Thing is, it is your project, do it your way and have fun. If you make any mistakes you don't like the next one will be better.

I don't know how available they are, but the TO3 case style of LM317 is a bit more robust, assuming you use a matching heat sink.

Ham fingered the schematic, heh? Don't hold back Sargeant, tell us like it is!

 

How about my idea of using a dual pot?

That's fine - as long as you connect the wipers to one end or the other of the pot. I prefer to use 10 (or more) turn pots on supplies; that way I don't have to use two in series.

You can actually use a pot of nearly any resistance value you have available if you use it to control an opamp as a voltage follower. However, unless the opamp has rail-to-rail inputs and outputs, your regulator output minimum will be around 3v.

 

Ham fingered the schematic, heh? Don't hold back Sergeant, tell us like it is!

Geeze, and here I'm trying to be all nicey-nice and stuff.

 

I've build a supply very much like the one you're building, a single turn is plenty fine resolution in my experience. Thing is, it is your project, do it your way and have fun. If you make any mistakes you don't like the next one will be better.

I don't know how available they are, but the TO3 case style of LM317 is a bit more robust, assuming you use a matching heat sink.

I've built power supplies with this Ic before but the fact is I didn't take my time to analyse what does what.. Just a supply for my need.. This time I'm making it better.. thats all.. So many heads are better than one for ideas... And its cool to discuss things with you guys and learn what I don't know..

And Op-amp controlled supplies.. maybe next time.. My classes are starting so time will be a big problem..

Bill, what about the transistor for your circuit??

 

Bill, what about the transistor for your circuit??

I'm not Bill, but any common PNP transistor would work, such as a 2N2907 or 2N3906. The problem is the power loss in Rs.

The transistor will begin to turn on when Vbe is around -0.63v. So, if you want the LED to come on before the LM317 is overloaded, you'll use around 0.63 Ohms for Rs, which will cause the LED to begin to light up at around 1A current.

If you use 1 Ohm for Rs, the LED will light up when over around 0.63A current flows through it.

 

Ohh Thanks.. I'm not going to put that into this anyway.. Just wanted ideas on how to.. My idea was to use a relay

 

Actually I specified test select, 1Ω or less. If I were going that far I'd either put a current foldback or (more likely) constant current source for current limiting.