Hello, I have a circuit below from this website here and it is a backup led circuit for when the mains powers fails.
In this circuit the 230v mains supply is rectified and R2 and C2 are used to smooths out the Dc voltage and this voltage powers the combined forward voltage of the LEDs and before the end of the LED string, power is tapped to turn on the Photo-coupler which pulls the base of the PNP transistor high, thus keeping it off. When mains power is turned off the pnp transistor is pulled to ground through a resistor, thus turning it on and supplying current to the back-up LEDs.;
- Is the way i explained it correct?
2)Is capacitor C1 (105 J/400v CBB22) used to step down the voltage, an alternative to
3)What is the purpose of R3 and R4?
4)On the website it say switch1 (S1) is used as a power switch for the circuit but why is
9v need at the top of S1?