3A Adjustable 3 30V Regulated DC Power Supply

This power supply is meant as an auxiliary or as a permanent power supply for all common circuits based on a stabilized DC voltage between 3 and 30V provided that the consumption does not exceed 3A. Of course this power supply unit can also be used for other purposes. Be replacing the trimmer by a potentiometer, it may even be used as an adjustable power supply unit. A good quality heatsink must be used.
[...]
Parts list:
R1 = 8.2K
R2 = 2.2K
R3 = 680R
R4 = 1K
R5 = 82K
R6 = 0.18R/5W
C1 = 470p
C2 = 100nF-63V
C3 = 100nF-63V
C4 = 100uF-63V
C5 = 10KuF-60V
D1-D6 = 6.6A
Q1 = MJ3001 (Darligton)
IC1 = UA723D
Specifications:
* Overload protected
* Sshort-circuit stable
* Output current: max. 3A
* Output ripple voltage: 0.5mV
* Output voltage: adjustable from 3 to 30V, stabilized
* Input voltage: 9 to 30V AC (depending on the desired output voltage)

Source: http://www.extremecircuits.net/2010/02/3-30v-3a-adjustable-regulated-dc-power.html

Read More

Dual Regulated Power Supply Circuit Diagram

In this circuit, the 7815 regulatates the positive supply, and the 7915 regulates the negative supply. The transformer should have a primary rating of 240/220 volts for europe, or 120 volts for North America. The centre tapped secondary coil should be rated about 18 volts at 1 amp or higher, allowing for losses in the regulator. An application for this type of circuit would be for a small regulated bench power supply. 

 Dual Regulated Power Supply Circuit Diagram

Read More