Power Supply


Video tutorial Electrical Transformer + AC to DC conversion

Afroman covers the basics of how transformers work, where to shop for step down mains transformers, and how to wire one up to mains voltages without killing yourself. European and North American wiring is discussed. He finishes up with a quick example of AC to DC conversion in an unregulated dual rail power supply.
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer’s coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer’s core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or “voltage”, in the secondary winding. This effect is called mutual induction.


LM317 Adjustable Voltage Regulator video Tutorial

A tutorial on the LM317 voltage regulator. Shows you how to make a 1.25 to 25V adjustable voltage supply, or choose any other output voltage you want. An example of a fan speed controller is shown.

The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages which are easily mounted and handled.

In addition to higher performance than fixed regulators, the LM117 series offers full overload protection available only in IC’s. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected.

Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators.

LM317 Adjustable Voltage Regulator video Tutorial - how to make a 1.25 to 25V adjustable voltage supply

 Datasheets LM317


Video turorial Voltage regulator tutorial & USB gadget charger circuit

This video covers the basics of linear voltage regulators – what they do, how to wire them up, and where to find them. Then I give a basic example of how to build a 5V supply that can be used to power USB powered gadgets.
The LM341 and LM78MXX series of three-terminal positive voltage regulators employ built-in current limiting, thermal shutdown, and safe-operating area protection which makes them virtually immune to damage from output overloads.

With adequate heatsinking, they can deliver in excess of 0.5A output current. Typical applications would include local (on-card) regulators which can eliminate the noise and degraded performance associated with single-point regulation.