You can buy a dedicated voltage regulator such as the LM138 and comes with plenty of example circuits in the datasheet (see below).
http://www.ti.com/lit/ds/symlink/lm138.pdf
TL431 plus driver transistor (BD135) for the 2N3055, creating a Darlington stage.
TL431 plus driver transistor (BD135) for the 2N3055, creating a Darlington stage.
Those are good ways of improving the original circuit. The datasheet even has some application circuits, to make simple power supplies.
Such as this one:
The part numbers in the LM138 series which have a K suffix are packaged in a standard steel TO-CAN package, while those with a T suffix are packaged in a TO-220 plastic package.
The LM138 is rated for TJ = –55 C to 150 C, and the LM338 is rated for TJ = 0 C to 125 C.
If 680 ohms is to high, what value would I need to obtain the 3 Amps maximum current ?
Thank you for all your replys, I have put together various circuits with 3 terminal linear regulators, using the LM317 and LM338, also 78XX regulators. I never tried the option of trying a zener diode as a regulator. Thought it would be good to try it, so the source is in the link below. If 680 ohms is to high, what value would I need to obtain the 3 Amps maximum current ? I have ordered some 3 watt 680 ohm resistors, just going on the value of resistor from the source of the diagram. Thank you for the schematics, if the first attempt works OK (my building it) sure I'd love to try these improved circuits you've posted up.
http://www.circuitstoday.com/12-v-high-current-regulator
Thank you for all your replys, I have put together various circuits with 3 terminal linear regulators, using the LM317 and LM338, also 78XX regulators. I never tried the option of trying a zener diode as a regulator. Thought it would be good to try it, so the source is in the link below. If 680 ohms is to high, what value would I need to obtain the 3 Amps maximum current ? I have ordered some 3 watt 680 ohm resistors, just going on the value of resistor from the source of the diagram. Thank you for the schematics, if the first attempt works OK (my building it) sure I'd love to try these improved circuits you've posted up.
http://www.circuitstoday.com/12-v-high-current-regulator
I think the first time I was shown that circuit was in a school textbook, which had the transistor as a BFY51. Using that transistor I made a small PSU to provide 9 volt and it worked fine for building small circuits while at college. I built the circuit with some veroboard and placed it inside a small black box with a minature transformer and a 1 metre length of wires with clips on.
That's interesting, I've bookmarked it, thanks for the link. Some ideas to try beyond the first circuit. I have looked about at 5 watt zener diodes, do you think the 1N5350B diode would be of use, given its higher power rating ? I've got 1.3 Watt 13 Volt diodes, but wandered if the 5 watt diode would give more flexibility.
TIP142. - Bipolar (BJT) Single Transistor, NPN, 100 V, 125 W, 10 A, 1000 hFE
Transistor Case Style: TO-247
These ST Darlington TIP142's are 99p each (£0.99), 125 Watts and Hfe=1000.QuoteTIP142. - Bipolar (BJT) Single Transistor, NPN, 100 V, 125 W, 10 A, 1000 hFE
Transistor Case Style: TO-247
http://uk.farnell.com/stmicroelectronics/tip142/transistor-darl-npn-100v-10a-to/dp/1653637