Minimizing power consumption of an Uno?

Hi all. I can't use a board other than the Uno and I'm on a tight power budget. What are all the ways I can reduce power draw?

Thanks for your help.

(If all else fails I can save quite a bit of power by switching my linear actuator to 5V instead of 12V, but that's an expensive solution.)

Use offboard switching regulator to make 5V for the Uno vs knocking 12v down to 5v with the onboard heat dissipating regulator.
Run the Uno slower 8 MHz, 4 MHz - see the clock portion of the datasheet.

What is the base power draw with nothing attached with an empty sketch?

aoeud:
What is the base power draw with nothing attached with an empty sketch?

Surely you have a meter and can measure that* yourself?

If you don't have a meter, you really really really should get one tout de suite.

*edit: Well the current anyway, not the power as such, not with a standard meter

I’m really not sure how to fit the multimeter between the USB cable and the Arduino. Or even with a wall wart. Where do you put the damn thing?

aoeud:
I'm really not sure how to fit the multimeter between the USB cable and the Arduino.

Yeah I guess that might be tricky.... maybe sacrifice a cable and peel it open and break one of the conductors?

I once tried to measure the voltage at the end of a usb cable and found it very tricky not to short things, so good point.

You could maybe use a battery and provide power to the barrel jack or the Vin, which might make using the meter a bit simpler.

aoeud:
Hi all. I can't use a board other than the Uno and I'm on a tight power budget.

That is what I would call between a rock and a hard place. Please describe the power budget.

aoeud:
What is the base power draw with nothing attached with an empty sketch?

The USB->serial converter chip is also taking current, if you want micro-power
behaviour the Uno is the wrong board. A bare-bones board or similar is needed.

aoeud:
What is the base power draw with nothing attached with an empty sketch?

Oh around 40mA or so is a good guess. As others have said it's not a good board for trying for minimum current consumption what with the power on led, usb serial convertor chip, voltage regulator consumption, etc.

Oh... If the base is around 40 mA that really gets me out of this problem, though I have to keep everything on. I only have a ~5 mA chip, a small LED and a motor shield (where the motor itself is externally powered). For some reason I was thinking 250 mA, I'm not sure where I got this from. I had 500 mA to work with and a linear actuator taking 300 mA and possibly a second Arduino. That seems quite possible now.

Thanks for your help.