|
Hi Stuart,
Never heard of a safety diode. There are only normal and zehner diodes used in regulator circuits. A 78XX regulator is to regulate a positive voltage into the voltage were the xx are, e.g. a 7812 is to make from any voltage above 15volt a stable 12 volts. These can handle 1Amps, while the letter M in the middle is the 0.5Amp version and an L in the middle is the 0.1Amp version. The small cap (4u7) on the output pin3 is to reduce noise and oscillation. The big cap on input pin1 is to smoothen humm from the AC transformer. If there is a chance of reverse polarity like supply with a plugpack, a diode is sometimes used here. The diode only conducts if you connect a supply with the wrong polarity. The band goes to pin1 and the other side to pin2 (ground). Sometimes a zehner is used here if there is a chance of too high voltage or spikes e.g. a 24volt zehner. Connect the same as the normal diode. A 79xx is just the same, but for negative voltages. The diode bands go the other way and so do the caps. Take care here. The 79xx has another pinout. 1=ground, 2=in, 3=out. Hope this helps..
|