Hi Everyone,

I just wanted to say you guys are GREAT!!! I didn't expect so much help but you all came through for me. I really appreciate it guys...


Thank You,
StephenMG

 

I posted a constant current solution in StephenMG's other thread, and he just abandoned it. Why start another thread?

 

Yes I was getting around to something similar to Ken's. His has the advantage of a modicum of adjustment.

Points to remember.

When not immersed may transistor will drop the full battery voltage so must be rated accordingly.
For this reason do not try the FET circuit referred to in post #2.

The polarity may be reversed by using an NPN transistor and reversing the LM385.

Either way the pass transistor needs to be about 500 mWatts or greater rating.

This circuit won't work without a path for transistor base current, and also some bias current for the zener. A resistor to GND is the simplest solution.

 

Hi Ron,

I'm sorry for creating another thread... I just think that I was confusing everyone as well as myself. So, I created this one and tried to provide more information for everyone to go on.

Thank You
StephenMG

 

Hi Ron,

I'm sorry for creating another thread... I just think that I was confusing everyone as well as myself. So, I created this one and tried to provide more information for everyone to go on.

Thank You
StephenMG

OK, I'll let it slip this time. Just see that it doesn't happen again.
The problem it caused for me was, I thought you had dropped off the screen, because I don't check every new thread that appears.

 

Ron,

Don't worry, your included when I say you guys are good I thought I had a decent background in electronics but then when I came here, I realized that I don’t.

It is nice to know that others are so willing to help. Keep up the good work guys.

Thank You,
StephenMG

 

Oh, just found that Radio Shack carries this part:
http://www.radioshack.com/product/i...entiometer&kw=potentiometer&parentPage=search

It's a 1K Ohm 15-turn cermet pot. If you get one of those and use it for the 1k pot in the 2nd schematic I drew up, you won't need the 10K pot.

Having a small adjustment screw is better than a couple of big knobs that some goof might twist just to see what it does