To do a low-voltage power grid frequency detection system.

I want to make a low-voltage power grid frequency detection system, which mainly includes frequency conversion circuit (220v converted to 5v ttl level), single-chip detection, liquid crystal display, VB host computer monitoring

Temporarily purchased transformers, capacitors, inductors, transient diodes, zero-crossing comparators, etc. of the frequency conversion circuit, as well as the single-chip minimum system (chip, supporting base), lcd1602, keyboard module and serial port rs232

The great gods and predecessors can first help to see if the components are enough and whether there are any good methods for grid frequency detection.