The core problem is you don't know how to adjust the pot in your simulator, if you set the pot in the position for 0 amps then that is what you will get. If you set the pot for the other end (maximum current) then that is what you will get. Because this is a variable component you set it for what you want.

To prove my point try the following...

You will find the current is a shade over 30ma.

A question for Wookie, I had thought of the temperature variability in the diodes, would feeding them with a LM317 constant current source help? Before you jump on this Smilem, all electronics is suseptable to temperature variation, I'm just curious if it can be minimized.

 

A question for Wookie, I had thought of the temperature variability in the diodes, would feeding them with a LM317 constant current source help? Before you jump on this Smilem, all electronics is suseptable to temperature variation, I'm just curious if it can be minimized.

Variations due to temperature can be minimized by excellent thermal coupling between the semiconductors.

Even the LM317L will have some minor fluctuations over temperature, but with that regulator, nearly all components (save the external resistor) are mounted on a common substrate. Good thermal coupling to ambient air temperature will minimize these fluctuations.

If smilem really wants to have decent results from a relatively simple circuit, he could look at using his existing LM317L/LED circuit with either using the ICL7660 charge pump or the LT1054 charge pump wired as a positive doubler. The latter will probably result in a more stable source, as it has 10x the capacity of the ICL7660 charge pump.

The trouble is that our OP desires to have a great deal of accuracy, but has exhibited a lack of electronics knowlege, and for some unknown reason does not furnish complete details, and argues against advice presented.

I don't really know where this thread will wind up at the moment, but I have a strong feeling that unless our OP somehow miraculously develops some electronics skills overnight, the ending will not be satisfactory.

Smilem had a system that was working perfectly fine, and then he wanted to adapt it to a laptop powered item. Just getting to the point where smilem was using an LM317L that was rated for proper regulation at the desired current was nearly like pulling teeth, and now smilem wants to change everything.

I feel that this project is not worth the cost to other members who will be left twisting on the vine for assistance while this project is continually addressed.

However, if other knowledgeable members wish to contribute towards helping smilem develop a laboratory-quality LED driver, you are most welcome to do so.

I simply do not have the time, nor patience anymore.

 

The core problem is you don't know how to adjust the pot in your simulator, if you set the pot in the position for 0 amps then that is what you will get. If you set the pot for the other end (maximum current) then that is what you will get. Because this is a variable component you set it for what you want.

To prove my point try the following...

You will find the current is a shade over 30ma.

A question for Wookie, I had thought of the temperature variability in the diodes, would feeding them with a LM317 constant current source help? Before you jump on this Smilem, all electronics is suseptable to temperature variation, I'm just curious if it can be minimized.

My POT is set at 500 ohms and set at 50%. Q2 is 2N2222A
My project files are attached.
Thanks, I'll try that. Perhaps someone could answer to my post #39?

 

The 7805 will not work, under any circumstances, in a USB port setting. Is that the question you were referring to?

I notice you are listing 12VDC. Are you changing the conditions again? USB only has 5V, if you are going with a wall wart then why mess with 5V?

If you remember I mentioned the moving target on design, which you choose to misunderstand and tell me there was no comparison between a light tree and your project. The comparison is there. Pick a design goal and stick with it, jumping around alienates people who are trying to help. Our time is valuable to us, and there are other people who won't do this (and do their homework).

 

The 7805 will not work, under any circumstances, in a USB port setting. Is that the question you were referring to?

If I change LM324 to OP200 there seems to be very good stabilization or my simulator is not right. Therefore you could make the circuit work on 12V as intended by design and on 5V bypassig the current stabilization IC.

I notice you are listing 12VDC. Are you changing the conditions again? USB only has 5V, if you are going with a wall wart then why mess with 5V?

It would be better if it would work from 5V as I allready mentioned. But if I can't get a working suggestion how to make it then 12V whats left.

If you remember I mentioned the moving target on design, which you choose to misunderstand and tell me there was no comparison between a light tree and your project. The comparison is there. Pick a design goal and stick with it, jumping around alienates people who are trying to help. Our time is valuable to us, and there are other people who won't do this (and do their homework).[/QUOTE]

I'm not moving the target, this circuit can work on both 12V and 5V correct me if I'm wrong.

Also google threw up this PDF MAX6126 http://datasheets.maxim-ic.com/en/ds/MAX6126.pdf with a current statiblization diagram on page 14. If I understood it right it can work from 5V and has 2 digit after decimal point stability. If you can confirm this and help me choose remaining tranzistor and resistor than perhaps we can at last get the sollution I'm looking for.

 

I've done what I can. Yes, you are moving the target. I gave you a design, you did everything in your power to make it not work, ignoring suggestions along the way, and you are waffling between designs. I won't help with the other one, I really do have better things to do. If you have a question about mine I will try to help, but that is it.

My suggestion, take time to read, and learn, electronics. The only way you will ever be satisfied is if you do it yourself. Wookie and I are pretty active here. We have each gone 12 pages or more answering questions for people trying to learn a new concept. This is not what is happening here though, we keep revolving around the same limited area, like some sort of chaos funtion, but never going any where.