If your single-chip computer system power is not high, you can use LM7805 directly.

If the power is high, don't use LM7805. This is a series regulated power supply module, which consumes a lot of electricity, generates a lot of heat and is easy to burn out. Then I suggest using LM2576-5.0V This is a switching power supply module, which is also very convenient to use, as long as a few parts are needed (LM2576, diode 1N5822, plus a 65438+). You can download the user manual of LM2576 and use typical application circuits. If you have an email address, I can send you one.

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