The main circuit is powered by your 13.8 V bench ... The diode is referenced to a voltage divider, and voila! Your LM7805 is now putting out a steady 9 V. How did [0033mer] become adept at doing ...

just build this circuit on a breadboard and ‘unbrick’ by holding down the button. The circuit seen above is a High Voltage Serial Programmer. This is one of two high voltage protocols used by ...

The circuit of a voltage divider may be drawn with the two resistors vertical, not horizontal. If there are two resistors in series across a voltage source, then the circuit is a voltage divider.