I want to use a schematic that is designed to run on 12V, if I were to change this to 4.5V what alterations would I need to make to the circuit?

I presume the resistors would need changing, is this just an ohms law calculation? What else would need changing?

Thanks

(Schematic attached)

 

You wouldn't be able to run 3 LEDs in series. Depending on the forward voltage, you might have to run them all in parallel with their own current limiting resistor.

 

You wouldn't be able to run 3 LEDs in series. Depending on the forward voltage, you might have to run them all in parallel with their own current limiting resistor.

Yeh I don't intend to, I should have said that, sorry. That side of things I can make sense of anyway, it's everything else I need help with!

 

The only other thing to worry about is the threshold voltage of the MOSFET; it needs to be low enough that it turns on completely at the lower voltage.