In this video:

* Using spare parts to build a simple AC to DC power adapter / supply:

Parts used:- transformer, full wave bridge rectifier with Schottky (rectification) diodes, smoothing / filter capacitor, voltage regulator (LM7812 / Zener diode), resistor and LED to display operation.

* Electronic DC load to test the PSU, oscilloscope to view signal, Multimeter to measure output.
* How to calculate RMS voltage?
* How to calculate capacitor value?
* How to calculate ripple voltage?
* How to calculate the resistor value to run an LED?

This is a simple means of calculating the required size of the input filter capacitor in a basic power supply, or calculating the peak-to-peak ripple voltage in an existing supply. It works by assuming that the capacitor supplies current to the load approximately 70% of the cycle—the remaining 30% is supplied directly by the rectified voltage and during this period the capacitor is charged as well:
http://www.electroschematics.com/7048…

* Electronics Tutorial #5 – Ohm’s Law Pt 2 – Application:LED Resistor, Voltage Divider, Current Shunt – http://www.youtube.com/watch?v=AWLJAD…

* Electronics Tutorial #7 – Diodes – Zener, Schottky, LED, Silicon – http://www.youtube.com/watch?v=e2qCGp…

* Electronics Tutorial #8 – Diodes – practical applications – http://www.youtube.com/watch?v=d4Z8VI…