You could go with 9V and replace the LM317 with a simple resistor (assuming Vf =3.6 then R2 would be 18Ω). I only use the LM317 because I like it, but it isn't that special overall.
There are also other ways to regulate current that drop a lot less voltage. Take the circuit below, reverse the polarity, use PNP transistors, and it would do the same thing as the LM317 shown. The emitter resistors would be 7Ω or so.
Generally transistors in these designs are not critical, the 2N2222 and 2N2907 (its compliment) are as generic as they come, since you're in the UK go with whatever is closest. Same thing with the diodes shown, almost any small signal or power diode will work, in other words, junkbox parts.
This circuit will drop a minimum of 0.8 volts. You have two LEDs that are 3.6V worst case, so that would be 7.2V + .8V, or 8V. If you're using a 9V battery this will be sucked dry in less than an hour with that kind of current though.
The resistor R2 is 12.5Ω, you could use a 12Ω or a 13Ω, or a 13Ω in parallel with a 330Ω. Don't forget, these resistors are usually ±5%. You can always make custom values by using parallel resistors.
There are also other ways to regulate current that drop a lot less voltage. Take the circuit below, reverse the polarity, use PNP transistors, and it would do the same thing as the LM317 shown. The emitter resistors would be 7Ω or so.
Generally transistors in these designs are not critical, the 2N2222 and 2N2907 (its compliment) are as generic as they come, since you're in the UK go with whatever is closest. Same thing with the diodes shown, almost any small signal or power diode will work, in other words, junkbox parts.
This circuit will drop a minimum of 0.8 volts. You have two LEDs that are 3.6V worst case, so that would be 7.2V + .8V, or 8V. If you're using a 9V battery this will be sucked dry in less than an hour with that kind of current though.
The resistor R2 is 12.5Ω, you could use a 12Ω or a 13Ω, or a 13Ω in parallel with a 330Ω. Don't forget, these resistors are usually ±5%. You can always make custom values by using parallel resistors.
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