As the main cap voltage falls the led current falls – to the point where there is not enough Vbe to keep the pnp on, which starves the base of the npn – so the whole circuit snaps ... only there to ...

While addressable LED strips are all the rage ... to light until approximately 18V is across them. By adding a 15 V Zener diode and a resistor across the MOSFET which dims the LEDs, a voltage ...

Not if you’ve watched [0033mer]’s Simple Electronic Circuit Hacks video! You know just what to do. The ground pin of a LM7805 connects to the cathode of a TL431 programmable Zener diode pulled ...