High amperage regulated power supply help

Hi guys, I'm trying to build a high power regulated power supply for a 12v fan (need about 30A at 12V) control and I found a website where such a power supply is discussed.

In these pictures a power supply is laid out according to attachment.

However, I'm not really getting how the voltage regulator is capable of controlling the output voltage without any kind of loop back.

Also, when I put it together I'm getting a .3v drop between each of the stages of transistors, is this normal? eg from vr I get 8.97v, but after the first mje3055 I get 8.69v, and after the 2nd set of amplification I get 8.3v. Is that normal?


Thanks guys, I'm a total beginner when it comes to circuits but I'm trying to learn as this stuff is really interesting.

Hi,

From reading your many other posts, I strongly urge you not to make a 30 Amp power supply (if it is actually 30 Amps). Practice with a circuit that needs a MUCH smaller current draw first.

That circuit looks odd to me. For example, a 1 Ohm resistor into a transistor base is not normal. Even from a 7805, 5V/1R = 5A. I doubt any BJT needs 5 or 12 Amps to drive it's base. The 78xx family certainly can't output more than about 1Amp.

Try to use application notes and design notes by semiconductor manufacturers rather than things you find off websites.

My advice: Electronics is 10% doing and 90% reading and learning before the doing. 99% doing and 1% reading and learning is not a sensible or effective method and can even be dangerous.

The regulator is supposed to output a stable voltage. The "control loop" is inside the regulator.

You say in another thread you haven't touched electronics in twenty years, the best approach is reading a book on basic principles first to understand what should be happening and why, I think.