12v - stepdown or directly via Arduino?

Hi,

I use a 12v power supply (3S lipo). I drive 2 stepper dirvers, 3x Ultrasonic, 2x IR sensor and 1x XBee (directly via 3.3V). I may add more later. Till now the 800ma max (http://playground.arduino.cc/Main/ArduinoPinCurrentLimitations) should be more than enough. --> in theory I have three clocked step down supplies lying around.

From your point of view, does it make sense to:

1) Keep everything as it is (most simple) 2) Step down 12V to 7V and keep supplying everything via the arduino 3) Step down 12V to 5V supply and supply the sensors and stepper drivers from this supply. Keep the 12V supply for the arduino. 4) Better idea?

Thanks Robert

So this is a vehicle? And it is battery powered. so you want to loose the least amount of power possible. The arduino regulator is linear, stop using it, use a 12V to 5V switcher (dc-dc converter) that is big enough (current wise) to cover your future needs.

Where is the 3.3 coming from?

-fab

Yes, it's a robot. I started switching to the dc-dc converter for 5V. The 3.3v for the XRF http://ciseco.co.uk/downloads/documents/datasheet%20-%20XRF%20v1-6.pdf I get from the arduino mega, backed up with a cap. It's within specs (36ma when sending). Setting up an own converter just for this conflicts with the space limitations I have on the robot. But when I need to hook up more 3.3v devices, I'll need to do the switch anyway.

Thanks Robert