How to Use a Bridge Rectifier
There are two kinds of electricity: Direct Current and Alternating Current. DC always flows in one direction, although the volume of flow may increase and decrease. AC periodically changes direction. Many electrical devices need steady DC to function correctly, but AC travels better, so AC is what the power company delivers to your house. A rectifier changes AC to DC; an alternator changes DC to AC. One of the most common types of rectifiers is the bridge rectifier.
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Instructions
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Change the voltage level of the AC with a transformer. Generators put tens and hundreds of thousands of volts on the power lines. There is a transformer -- it looks like a cylinder several feet high -- on the power pole that steps the voltage down to 120 volts before it comes into your house. Some devices have a transformer built into the power cord to step the voltage down even further. The first stage of a bridge rectifier is to step the voltage down to the desired level with a transformer.
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Connect the four diodes in a series to make the bridge. Diodes are devices that allow current to flow in one direction but not in the other. If the bridge is arranged as a square with a diode on each side, AC coming into two opposite corners becomes "rippling DC" coming out the other two corners. A graph of AC shows a smooth wave that is positive half the time and negative half the time: current flows in one direction, then reverses and flows in the other direction. The DC that comes out of the bridge is always positive, that is, always flowing in one direction, but it is rippling, varying quickly back and forth from zero to the maximum.
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Smooth out the rippling DC to make the flow more uniform. You can do this with one or more "LC stages." Each LC stage runs the current through a coil whose capacitor connects across the circuit just before the coil. As the current builds toward a maximum value, the coil creates a magnetic field that opposes the flow and causes charge to build up on the capacitor. When the flow starts decreasing, the magnetic field starts collapsing and the charge on the capacitor adds to the flow through the coil. An LC stage cuts off the peaks and fills in the valleys to make the rippling DC smoother. Each LC stage makes the DC smoother.
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Tips & Warnings
If not much smoothing is needed, the LC stages can be RC stages, with smaller, cheaper resistors replacing the coils.
RC stages use up more power and create more heat than LC stages.
References
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