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anyone got measurements of Arduino Nanos power consumption ?

It guess it should be less than e.g. of the Uno or Mega as the USB Part only get powered when connected via usb and so does the 3.3 Regulator.

Also I should be able to easily disconnect the 5 V regulator and use a DC-to-DC converter instead with ~87% efficiency 34V -> 5V . More or less there should be not much more left than the LEDs (can be disabled by software to only blink every some seconds ?) and the Atmel 328P itself?

It will be able to sleep alot and beeing woken up by watchdog timer every 8s for some measurements and communicaton

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  • \$\begingroup\$ I measured power consumption of ATMega328P at different voltages and frequencies and made this chart docs.google.com/spreadsheets/d/… It's a bare microcontroller though, additional things on your board will consume extra power \$\endgroup\$ – Cano64 Feb 23 '16 at 16:08
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According to the schematic, the FT232RL (which is the 3.3v regulator as well) on the Arduino Nano v3 is powered from the 5v line. Regardless if you use USB or VIN or a 5v in. As does the blue power led4 (680Ω resistor means 2.5mA). Led1 and LED2 are controlled by the FT232RL, so should only be on when there is usb/serial communication. Only LED3 is controlled by the arduino D13 pin.

According to this page, the Nano takes 20mA when running, 17mA with the blue power led removed. That is not standby/power down current, which should be a lot lower. The FT232RL has between 15mA full operational current, to at most 2.5mA or minimum 70µa (0.07mA) in USB suspend mode, or with reset pulled low. Since the reset pin is not used, I believe that it should be 2.5mA by itself without a usb cable plugged in, but can't be sure (the FTDI datasheet does not say). That is without any draw on the 3.3v regulator line.

You could remove the 5v regulator, or just ignore it and use the 5v pin to input the externally regulated 5v, which is almost exactly how the USB power is handled (that goes through a shockley diode to protect the USB when 5v is already present). But you should be aware of your regulator's actual efficiency. At a 29 volt difference, at say 5mA to 50mA draw, is it actually 87%? The datasheet's graphs will tell you.

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  • \$\begingroup\$ Thank you very much for pointing out that link and the rest of your reply! I don't have much time to respond now, but i'll come back to this later the day or tomorrow. I wanted to use this DCDC Converter instead produktinfo.conrad.com/datenblaetter/150000-174999/… On arduino.cc/en/Main/ArduinoBoardNano it says: "The FTDI FT232RL chip on the Nano is only powered if the board is being powered over USB. As a result, when running on external (non-USB) power, the 3.3V output (which is supplied by the FTDI chip) is not available" \$\endgroup\$ – UtzUni May 12 '13 at 8:10
  • \$\begingroup\$ @UtzUni According to the 2.3 manual and schematic (arduino.cc/en/uploads/Main/ArduinoNanoManual23.pdf) It is also powered from 5v. The v2.2 manual/schematic shows it's powered from vbus (arduino.cc/en/uploads/Main/ArduinoNanoManual.pdf) Then again, Arduino has shit documentation, so none of these could be correct. The arduino page, imho, is out of date. As for your regulator, it is listed as 10% minimum load, so 100mA, for that efficiency rating. That white sheet isn't too informational, a datasheet would be better. \$\endgroup\$ – Passerby May 12 '13 at 9:13
  • \$\begingroup\$ @UtzUni so it depends on which version you have. If the schematics are accurate (which the Arduino company is not known for 100% accuracy), anything past the v2.2 does have the ftdi chip powered with 5v in. Anything 2.2 and before does not have it powered unless usb is connected. \$\endgroup\$ – Passerby May 12 '13 at 9:15
  • \$\begingroup\$ I just bought one (not genuine i think) from ebay for 10,50€ free shipping, should arrive the next few days. I'll then measure and play around with the regulators etc to see if I can use it or better take a blank atmega328 or similar. \$\endgroup\$ – UtzUni May 12 '13 at 18:21
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I don't have Nano power consumption figures but you can look up the 328P consumption figures in the datasheet.

Beware that a vast majority of DC/DC converter going from 34->5 will not give you anything near the 87% efficiency you want at sub 1 mA consumption. Make sure you pick one that has very low quiescent current and have pulse skipping or some other 'snooze' mode to provide good efficiency at light loads, even then I strongly doubt you'll get anything about 60%.

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  • \$\begingroup\$ Thank you for hints about picking the right converter. At the moment I was going to play around with this one: produktinfo.conrad.com/datenblaetter/150000-174999/… It is Mothers day today, so I'll pause this till the evening or tomorrow, have a nice day! \$\endgroup\$ – UtzUni May 12 '13 at 8:10
  • \$\begingroup\$ I looked at the datasheet and the no load current of that regulator is 1mA. Meaning it will drain as much as your nano even if you just have it sit there and do nothing! It is horribly ill-suited for a power sensitive application. What is your use case that you need to go from 34V -> 5V? \$\endgroup\$ – EEToronto May 12 '13 at 19:58
  • \$\begingroup\$ powered by 8 lipo batterys in series, the arduino should be build into a battery management system \$\endgroup\$ – UtzUni May 12 '13 at 20:19
  • \$\begingroup\$ You can use something like LTC3642 It will give you about 60% efficiency at 1mA to 0.5mA. \$\endgroup\$ – EEToronto May 12 '13 at 20:48

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