on video Turn your 12v adeptor into adjustable Power supply 3V to 20V

I will show how can you adjust the voltage of a 12V Adaptor to 3 volt to 25 Volts . here they used Externally, the TL431' operation is straightforward. If the voltage on the ref pin input goes above 2.5 volts, the output transistor conducts, causing current flow between the cathode and anode pins. ... Thus, the power supply uses the TL431 to keep the output voltage stable. but here we using A Variable resistor 10K to adjust the voltage from 3volt to up to 20V ( Not recommend more then 15V)

I will show how can you adjust the voltage of a 12V Adaptor to 3 volt to 25 Volts . here they used Externally, the TL431' operation is straightforward. If the voltage on the ref pin input goes above 2.5 volts, the output transistor conducts, causing current flow between the cathode and anode pins. ... Thus, the power supply uses the TL431 to keep the output voltage stable. but here we using A Variable resistor 10K to adjust the voltage from 3volt to up to 20V ( Not recommend more then 15V)