TCC
Thanks for the question -
I'm not sure if you have the answer yet so here is my numpty's guide to LED lighting
THIS is totally from a doing viewpoint - theory (which I also know) can go hang for a moment
You have a 12V supply
LEDs light up with 3V - all of them (they light one way round and don't t'other)
so hanging 4 in series on a 12V supply will light 4 LEDS - any colour, any size, always
3V
may be too bright, and may be too much voltage for long term use - So Add another and run 5 in series off 12V
So to go back to your original question - pick off a new 12V supply and connect 4 or 5 whie LEDS in series across it.
Do not change anything in your diagram
White LEDS are readily available - in pound shops where they are called keychain lights - 2 for a pound or LED torches where 4 or 5 are fittted as "bulbs".
Viola - high power white LEDS!
Functional notes: Keychain lights connect a white (or other colour) LED DIRECTLY across a Li button cell battery (3V or a little more)
Torches may well have the LEDS connected in parallel to 3V - so you may need to persuade them into series connection if you wish to run from 12V. They will be fine across two pencells - ANY type
Car accessory shops sell very high power LEDS ready for connection at 12V - lots of colours, but more pennies
Please ask any further questions you like till you are happy (and lit up
)
I leave you with a wise ode from Mr FLJ who says:
"the shorter leg
goes to the neg"
andrew