I've see this topic discussed a few times, but have not yet found a thread with actual numbers published. I've some projects I'd like to make battery powered using NANO boards, IF the power use can be made low enough to make it worthwhile to do so. I've seen it mentioned that I can apply 5.0 volts directly to the 5V pin, and obviously doing so will mean less power wasted through the regulator. And I've also seen the idea of stripping down the board, or at least clipping the power pins on such things as the USB chip. But how much actual current usage drop could be gained doing things like this?
I've measured the current draw from a few NANO boards while running an application, just powering through the VIN pin at about 12 V. In that case I read from 22 to about 26mA. If removing all board electronics and pumping in 5V directly would cut that current draw down to 10mA or lower, it might be worthwhile. In fact I've found some very cheap and extremely efficient boost regulator boards that would allow me to power the board with a Li-Ion cell, and maintain 5.0 volts through the useful life of the cell. (product links offered on request). But if all I could expect to gain for this effort is only a few mA, I probably won't bother. Anyone try and mods like this and have some metrics to share?
Power consumption while awake isn't as simple a topic as you might think. You can reduce the draw while awake by running at a slower clock speed but then the microcontroller may end up needing to stay awake longer to get things done so unless the microcontroller is spending time awake doing nothing it's better to get the job done as fast as possible and then get back to sleep. So you will need to analyze your specific application to optimize for low power consumption.
Power consumption while awake isn't as simple a topic as you might think. You can reduce the draw while awake by running at a slower clock speed but then the microcontroller may end up needing to stay awake longer to get things done so unless the microcontroller is spending time awake doing nothing it's better to get the job done as fast as possible and then get back to sleep. So you will need to analyze your specific application to optimize for low power consumption.
That makes sense. I've heard of developers forgoing the 16 Mhz crystal and just going with the internal 8 Mhz. My app will have to be running all the time, though if there is a way to put it into sleep mode and wake periodically without an external pin toggle, I might be able to look into that. But still, it would be nice to know just how much is wasted by unneeded support circuitry. I'll look at the link you shared. Thanks!
You can wake it periodically by leaving the watchdog timer running, which increases the sleep current to 6.54 uA according to Nick Gammon's measurements in the page I linked.
