Current Regulator Supply

It will be cheaper, easier, and safer to just buy a 12 watt 24V DC power supply. The supply will already have the correct connectors for your power distribution and the correct failure protection circuitry.

This sounds a lot like a guitar amp or such. The op can check that out if he wants to make or modify one. Would the volume control adjust the m-amps?

GA for a really great and correct answer.

Many believe that its possible, some of them have posted here, yours was the first good & correct answer that I read from the top down......

It demonstrates yet again that even simple Ohm's Law is still not understood by many.......

Im not sure that he was in fact asking for a variable current, fixed voltage power supply. But rather a "limited" current supply. In which case it's a very simple circuit design. You can either go with a wire wound step down transformer or a "switchmode" supply. Use a wire wound if the apparatus you are supplying is sensative to electrical noise. "switchmode" is better off purchased unless your very familiar with SCR configurations. Connect the secondary in paralell with an appropriate full wave bridge rectifier. Half wave gives very unreliable DC. Then filter it by means of a capacitor (or several) in paralell with the rectifier output. The higher the capacitance the smoother the DC. This "pre filter" will improve the efficacy of a zener based regulator ten fold. Then obviously comes the regulator which can be proceeded with further capacitance in parallell, (generally much smaller than the pre-filter). You can then put a resistor (wire wound or carbon film, doesnt matter in this case) to limit the current in the circuit regardless of the load. Make sure you fuse your primary side. Calculate your fault protection at 24V not 220V. Hope this helps.

That could be true.

There are various circuits around to allow the building of such a supply, let us see what the OP can tell us what he wants precisely....

Actually i dont see any mistake in the question.he has asked for a constant 24V output which can provide 0-500mA current..
It is definitely possible..
Correct me if i am wrong..ur last sentence is same as the question..

It is possible for a single set of unvarying circumstances, but not in the manner the OP requires/requested.

If the load has a variable resistance, how will you always push 500ma through it?

For example, the load has a resistance of 10 Ohms. The voltage required to get 500 ma to flow is found as follows V = I x R = 0.5 x 10 = 5 volts.

For example, the load has a resistance of 100 Ohms. The voltage required to get 500 ma to flow is found as follows V = I x R = 0.5 x 100 = 50 volts.

For example, the load has a resistance of 1000 Ohms. The voltage required to get 500 ma to flow is found as follows V = I x R = 0.5 x 1000 = 500 volts.

(This was made using the simple Ohm's Law of V = I x R. If you need more infos there is quite a good dissertation at:- http://en.wikipedia.org/wiki/Ohms_law)

Therefore you cannot have a fixed voltage AND a fixed current in the way the op writes, with a variable load.

You can have a fixed voltage and a variable current UP TO THE MAX REQUIRED, this may be what he actually needs, though I am guessing. Or even a variable voltage and a fixed current as I demonstrate above.

As load varies, this means that the resistance of the load varies, many forget this!)

I hope this helps.

Post asked for a current regulator power supply [title of post], apparently variable 0 - 500 mA. Did not ask for constant voltage supply with overcurrent limit.

Since original post has not clarified his wish, or commented at all, we should give up posting on this.

This was made for 2.8V, 2 NiCd cell supply, but if you use LM10 not LM10C, it is OK for 30V battery supply.

Ok I would like to put this in another way…..

Assume we have a balloon filled with water….these two arrows shows potential difference (V) and circle show electrons flow at given period of time (A).

Now If I will press the balloon from arrows picture will be as shown below means….potential difference reduced and electron flow increased by new circle diameter. This is applicable for fixed power(V x I).

So, we have to vary one parameter to keep another one constant…at varying power.

Please correct…if wrong