Hello,
I've just made this power board.
I plan to use it to get two different voltages for two different circuits.
I first use one LM317 (in a TO-220) to lower the battery voltage (which is 14.8V) to 10V at the output. This voltage will be used to power several leds in series.
I then lower once again the battery voltage, in parallel, to lower the 14.8V to 5V at the output. This voltage will be used to power the arduino, a 32*8 leds matrix and a ventilator in the box where I'll put this power board PCB.
My question is, could this circuit work fine (that's one of my first schematics) ? I ask this question mainly because I don't know if we can put two LM317s in series. I thought of this method to prevent the temperature from rising too much (23.5°C/W) 
, but I don't know if we can do this 8).
Do you also think capacitors values are good choices?
Thank you for yout help !
That can work but it will probably overheat anyway (have you calculated the total current?) so you should probably consider buying or building a switching regulator (which will run cooler and can generally handle more current).
I first use one LM317 (in a TO-220) to lower the battery voltage (which is 14.8V) to 10V at the output. This voltage will be used to power several leds in series.
The normal solution is to use a higher value current-limiting resistor instead of a regulator. LEDs are "current driven".
Thank you, that's what I wanted to know !
DVDdoug:
The normal solution is to use a higher value current-limiting resistor instead of a regulator. LEDs are "current driven".
And (tell me if I'm wrong, I'm still a beginner) but I think that in my case a voltage regulator would be better suited as the battery's voltage varies with the discharge of the battery.
A couple of switching regulators will give you longer battery life as they do not dissipate nearly as much Voltage Drop x Current into heat as linear regulators do.
(14.8V - 10V) x current of LEDs = power dissipated as heat.
Dropping 14.8V to 5V is even more.
Some of these guys are 85-95% efficient.
CrossRoads:
Pololu - Voltage Regulators
Some of these guys are 85-95% efficient.
Thank you, I'll have a look !
