add-on #1: PS5
5V power supply

Description:

The power adaptor described here can be used to supply most every appolication on this site needing 5V power supply. Depending of used transformer and voltage regulator the output current can be up to 2 Amperes. Similar adaptor can be built for applications requiring 12 Volts. Again, the suitable transformer and voltage regulators should be used. The most suitable voltage regulators (that I use) are 78 series:

7805: voltage +5V, current 100mA..2A (depending on model);
7812: voltage +12V,current 100mA..2A (depending on model);
7815: voltage +15V,current 100mA..2A (depending on model).

An datasheet from Fairchild Semiconductor about MC78xx/LM78xx voltage regulators can be found here. The same devices are manufactured by almost every well-known manufacturer. This datasheet is in PDF (Adobe Acrobat) format. You can download Acrobat by clicking the banner below.

Transformer should be suitable for your local mains parameters. Some countries use 110/120 Volt at 60 Hz, some (like mine) 220/250 Volt at 50 Hz. Be aware of using a transformer designed for 120 Volt on 220 Volt! The opposite case (220 Vont transformer used at 120 Volt) is not dangerous, but you'll not get desired output voltage. The other dangerous thing about the transformer is that once you have proper transformer you should not swap its input and output. Swapping them should firstly burn the voltage regulator and probably the device powered by it, then should burn the transformer itself. Ofcource there is fuse in the input circuit, but who can say which part will burn first - the fuse or the transformer :-)

Schematic:

Used parts:

T1: Transformer 120/220V, 50/60Hz to 6..8V. Should be capable to give output current up to 200mA.
D1: Diode bridge. Could be in single package or made by standard rectifier diodes. Minimal working voltage 15V, typical current 200mA.
F1: Fuse 100mA. As faster as better.
C2,C3: Capacitors 100nF each.
C1: Electrolythic capacitor 500..1000 uF. Minimal working voltage 15V.
A1: Voltage regulator from 7805 series. Very good device. Has output shortcut protection (current limiting) and very good filtering capabilities (up to 75dB).