The bridge rectifier--also known as a full-wave rectifier--consists of four diode rectifiers configured to convert alternating current (AC) to direct current (DC). The rectifiers are available as individual diodes or as moulded components with the internal diodes already connected. The input to the bridge rectifier is an AC source, usually from the secondary of a 60-cycle power transformer. The output is an unfiltered DC voltage with a 120-cycle ripple. Typically, filter capacitors are added to the output to reduce ripple and produce a more usable DC voltage source.
- Skill level:
Things you need
- 4 power diodes
- Low-power soldering iron
- Rosin core solder
- Hookup wire
Solder the anodes of two of the diodes together to ensure a solid electrical connection. Use a low-power soldering iron and rosin core solder--be careful not to let the diodes get overheated. The symbol for a diode is a delta symbol or solid arrowhead touching a straight line. The end with the delta is the anode. Some diode manufacturers place a coloured band to identify the cathode. Others mark the cathode with a "+" symbol. If in doubt, check with the manufacturer's data sheets to see how the selected diode is marked.
Solder the cathodes of the remaining two diodes together. Look for the end with the straight line or other marking indicating the cathode.
Bend each of the diode pairs into right angles and place them side-by-side to form a diamond shape. Solder the two corners at the top together along with a piece of hookup wire. Tape a label on the other end of the hookup wire and mark it "AC". This will be the first of the two AC input lines which will eventually be connected to the secondary of an AC transformer.
Solder the two corners at the bottom together along with a piece of hookup wire. Label the open end of the hookup wire "AC." This lead will be the second AC connection to the secondary of the transformer.
Solder the hookup wire to the remaining corners of the bridge rectifier. The wire soldered to the connection that is anode to anode should be labelled as "N" for negative, while the wire connected from the cathode to cathode junction should be labelled "P" for positive. These are the two DC output leads.
Tips and warnings
- Make sure that you have correctly identified the cathode and anode of the diodes you have selected. There are many labelling conventions used by manufacturers.
- Consider using a heat sink attachment when soldering the diodes, as semiconductors are easily damaged by too much heat.
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