A Variable DC Power Supply is one of the most useful tools on the electronics hobbyists workbench. This circuit is not an absolute novelty, but it is simple, reliable, rugged and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A. Well suited to supply the circuits shown in this website.
http://www.redcircuits.com/Page36.htm
The LM317T is a adjustable 3 terminal positive voltage regulator capable of supplying in excess of 1.5 amps over an output range of 1.25 to 37 volts. The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm
Opamps are very useful. But one of their major drawbacks is the requirement of a dual supply. This seriously limits their applications in fields where a dual supply is not affordable or not practicable.
http://www.electronic-circuits-diagrams.com/psimages/powersuppliesckt1.shtml
These circuits can be used to supply low current DC accessory circuits by tapping into the DCC track supply Bus. This might be done if a regular DC supply was not available and the power required by the accessory was small.
http://home.cogeco.ca/~rpaisley4/xDccAccPSU.html
It uses 12V 5A transformer and some basic components to give put unregulated +12V. One resistor is used to reduce the current for the LED light.
http://www.ee.washington.edu/circuit_archive/circuits/Supply.GIF
This is a simple regulated power supply that can give adjustable voltage from 3 volts to 18 volts. The current capacity is 10 amperes. This circuit is overcurrent protected. This circuit can be modified for higher current ratings if needed.
http://www.anatekcorp.com/ttg/tiptrick.htm#10 amp Power Supply
This circuit provides 0-30 volts, at 1 amp, maximum, using a discrete transistor regulator with op-amp feedback to control the output voltage. This power supply has constant current mode suitable for charging batteries.
http://members.tripod.com/michaelgellis/power2.html
This is a simple circuit which can provide an adjustable voltage source of 0 to 330 Volt. The supply is short-ciruit proof. the current is limited to about 100mA.
http://www.geocities.com/tjacodesign/300vsup/300vsup.html
This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC.
http://www.electronics-lab.com/projects/power/003/index.html
It inputs AC100 V and it is possible to take out 12 V of the two DCs which are independent as the output.
http://www.hobby-elec.org/e_ckt19.htm