Arduino Nano DC Option

I am thinking of purchasing an Arduino Nano R3 board. Is there a way I can power this board with anything other than the 5v from the computer? I've noticed there is a Nano shield that provides a DC in, but I think it defeats the object as I want to keep my project as small as possible.

I thought there may be a mini usb to dc out there somewhere.

A Nano has a voltage regulator on it so can be powered by any Input Voltage normally between 7-12 V. You can also power it through a USB charger giving 5V. See:- http://arduino.cc/en/Main/ArduinoBoardNano

daz1761: I am thinking of purchasing an Arduino Nano R3 board. Is there a way I can power this board with anything other than the 5v from the computer?

Lots of ways, try reading the Nano page: http://arduino.cc/en/Main/ArduinoBoardNano

It says: Input Voltage (recommended) 7-12 V

Or use any regulated 5V phone charger, they're all over the place.

The Nano lacks a DC coaxial connector, but it does have the Vin and ground pins. If you want to run it at 7-12V, just connect + to Vin and - to ground. As mentioned above, you can also safely power the Nano by connecting 5V to the 5V pin, BUT be sure that you use a well-regulated 5V supply. Absolute maximum Vcc is 6 V and some poorly regulated supplies may exceed this, especially if your mains voltage is not all that stable.

The USB-serial converter chip gets its power only from the USB jack, so it won't draw power if you feed the Nano via either Vin or 5V.

Ciao, Lenny

LROBBINS: The Nano lacks a DC coaxial connector, but it does have the Vin and ground pins. If you want to run it at 7-12V, just connect + to Vin and - to ground. As mentioned above, you can also safely power the Nano by connecting 5V to the 5V pin, BUT be sure that you use a well-regulated 5V supply. Absolute maximum Vcc is 6 V and some poorly regulated supplies may exceed this, especially if your mains voltage is not all that stable.

The USB-serial converter chip gets its power only from the USB jack, so it won't draw power if you feed the Nano via either Vin or 5V.

Ciao, Lenny

That last statement is not true. The USB serial converter chip gets it's Vcc power from the same bus that the 328P chip does, so it's always powered up no matter what the board is using as a voltage source.

http://arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf

Lefty

Thanks for the replies guys :)

I totally forgot about using a USB power adapter on the USB cable :blush:

I've just noticed as you pointed out Vin and GND. If I wanted to run this controller from a 9v battery, could I go directly into these pins as its between the 7-12v scope?

Yes.

Thank you for the help :)

The USB-serial converter chip gets its power only from the USB jack, so it won't draw power if you feed the Nano via either Vin or 5V.

Ciao, Lenny

That last statement is not true. The USB serial converter chip gets it's Vcc power from the same bus that the 328P chip does, so it's always powered up no matter what the board is using as a voltage source.

Thank you lefty. Yes, it seems that the converter Vcc is the same 5V bus! Which leads me to a couple questions:

(1) If the MCU is put in PWR_DOWN sleep, how much does the FT232 still draw?

(2) Is there a way to eliminate the consumption of the FT232, or put it to sleep, short of cutting the trace to its pin 28?

AGAIN, A BIG THANKS FOR THE HEADS UP!

Ciao, Lenny

LROBBINS:

The USB-serial converter chip gets its power only from the USB jack, so it won't draw power if you feed the Nano via either Vin or 5V.

Ciao, Lenny

That last statement is not true. The USB serial converter chip gets it's Vcc power from the same bus that the 328P chip does, so it's always powered up no matter what the board is using as a voltage source.

Thank you lefty. Yes, it seems that the converter Vcc is the same 5V bus! Which leads me to a couple questions:

(1) If the MCU is put in PWR_DOWN sleep, how much does the FT232 still draw? Datasheet (linked below) says 15ma is 'normal load current'. (2) Is there a way to eliminate the consumption of the FT232, or put it to sleep, short of cutting the trace to its pin 28? The datasheet indicates there is some kind of 'suspend mode' that will allow the chip to draw typically 70ua of current. But I'm not sure what hardware/software support would be required to utilize that feature and if the PC USB driver software would support it. Check the datasheet I guess.

AGAIN, A BIG THANKS FOR THE HEADS UP!

Ciao, Lenny

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Lefty

Yes, Lefty, the data sheet says that current drops into the uA range in "USB suspend", but search as I may I cannot find anything in the data sheet that says under what condition it goes into USB suspend (by itself? When USB is disconnected? Under program control?). Ciao, Lenny

Not having found any information on how USB standby is invoked in the data sheet, I went to FTDI's web site. The only thing I found there was:

How does FTDI handle USB suspend?

USB suspend is controlled by the USB host telling telling the peripheral device to go to suspend.

The FTDI drivers do not force the FTxxx devices to go to suspend.

If the USB data bus is idle for >3ms the USB host should put the FTxxx into suspend.

Which still leaves me in the dark (but not hopeful) about what happens if the USB cable is unplugged. Ciao, Lenny

Which still leaves me in the dark

Why? It says that the FTxxx drivers do not suspend the chip, but any software using the drivers should. As the arduino is just using the drivers then they are not suspended and the device continues to draw full current.

Yes, Grumpy, that’s the way I read it too, but was just hoping that someone wold say - “well, if the USB cable is disconnected it does go to USB standby even if it has Vcc; we just forgot to mention that in the data sheet”. Looks like the only way to remove the drain of the USB-serial converter is to cut the trace that feeds its pins 4 and 20. Haven’t yet looked to see how hard that wold be to do, or whether it would be possible to add a jumper. Ciao, Lenny

LROBBINS: Yes, Grumpy, that's the way I read it too, but was just hoping that someone wold say - "well, if the USB cable is disconnected it does go to USB standby even if it has Vcc; we just forgot to mention that in the data sheet". Looks like the only way to remove the drain of the USB-serial converter is to cut the trace that feeds its pins 4 and 20. Haven't yet looked to see how hard that wold be to do, or whether it would be possible to add a jumper. Ciao, Lenny

Well one solution would be to rewire the FTDI chip to get it's Vcc from the USB +5vdc rather then the boards existing 5vdc bus. That would effectively power off the chip if not connected to the PC. The Seeeduino mega board I own does does just that, so that when using external power the FTDI does not draw any power unless it's actually plugged into the PC usb port.

Lefty

Taking a look at the pcb layout, it seems as though disconnecting pins 4 and 20 from the +5V line would be close to impossible, at least for me. They are bottom copper directly under the FTDI chip, which is of course under the MCU on the other side. A physical intervention would require de-mounting the USB-serial chip and then re-flowing it and that's not something I'm about to try. Yes, Lefty, tying those traces to the USB power rather than the 5V post regulator would be less cumbersome than using a switch or jumper.

Time to figure out what it means to say that a host goes to USB standby, what the various power modes D0, D1 etc. mean, and whether the Windows API would give me a simple means to do it.

I guess the other thing I should do is to make up a USB cable with the 5V line opened so that I can measure current from an external 5V with the PC in various states: connected, standby, hybernate, un-plugged.

Ciao, Lenny

Doesn't the following, quoted from http://www.beyondlogic.org/usbnutshell/usb2.shtml#SuspendCurrent imply that the FTDI should drop current draw if the USB cable is disconnected?

Entering Suspend Mode

A USB device will enter suspend when there is no activity on the bus for greater than 3.0ms. It then has a further 7ms to shutdown the device and draw no more than the designated suspend current and thus must be only drawing the rated suspend current from the bus 10mS after bus activity stopped. In order to maintain connected to a suspended hub or host, the device must still provide power to its pull up speed selection resistors during suspend.

Ciao, Lenny

Good news, and a bit easier to check than I thought. I didn't have to modify a cable or lift a pin on the USB mini-B jack.

I realized that I had a Nano on which I'd substituted a through-hole Shottkey for a fried D1. I just lifted one leg of that diode and put an ammeter between a 5V source and the 5V pin so that I could measure current with the USB plug connected or disconnected. Disconnecting the USB cable causes a roughly 9 mA drop in consumption. Not as good as one might think from the difference between the "typical" FT232Rl consumption of 15mA and it's USB standby of 70 microA, but the converter clearly does go to a low power mode when there is no USB signal. Moreover, the actual FT232 current of this particular chip with only the USB heartbeat running may be closer to 9 mA than 15 mA -- I have no way to know.

In any case, I am happy with this result.

(BTW, my setup also has MCP 2151 and 2551 CAN controller and transceiver connected to the Nano. Putting the controller and transceiver into sleep mode drops total consumption from 36.5 to 17.8 mA (with USB connected) or from 27.4 to 9.3 mA with (USB disconnected), so I also now know that the base consumption of an awake Nano is approximately 18mA with USB connected, and 9+ mA without. Next to test: how much further does it drop if the Atmel is put into ADC off and PWR_DOWN and how low can it go if I remove the LEDs.)

Ciao, Lenny

A correction:

As usual, my memory is less than stellar. Just a bit ago I wrote:

Next to test: how much further does it drop if the Atmel is put into ADC off and PWR_DOWN and how low can it go if I remove the LEDs.)

Well, when I went back to look at my sketch, I found that it already but the Atmel in ADC off and PWR_DOWN (with the transceiver awakened by CAN activity and MCU sleep, MCU sleep interrupted by activity on the CAN transceiver RxD pin and the MCP-2151 awakened by MCU activity ). So the 9+ mA in my previous post is mostly the parasitic load of the not-too-useful power LED and whatever loss occurs having +5V connected to the output of an input-less linear regulator - everything else is sleeping pretty soundly.

Ciao, Lenny