Solution to the heat dissipation problem of three-terminal volt
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LM1805 outputs 5V and LM1805 outputs 5V. It can also be made into a power supply that outputs 5V, 9V, 12V, -5, -9, -12, etc. It is no problem to solder them together, just add a heat sink to LM7805. Just pay attention to the positive and negative when LM1805 outputs -.
Use a 220V-12V transformer to step down the 220V, and then use 4 1N4007 full-wave rectifiers. Then connect an electrolytic capacitor above 1000uf/25V for filtering. Then connect a small capacitor of 0.1uf and then input pin 1 of 1805; pin 2 of LM1805 is grounded; pin 3 of LM1805 is output, and LM1805 adds a 0.1UF capacitor to the ground. Then it's OK. The input of LM1805 is not very hot when connected to 12V DC. The heat is related to the size of the load and the voltage drop. The input of LM1805 can be up to 18V; depending on the size of the load plus a certain size of radiator, generally, the load below 200MA does not need to add a radiator.