Arduino Mobile

The purpose of this PCB is to provide a board similar to the ARDUINO UNO but dedicated to embedded projects (ie powered by batteries).

Why ? Because you cannot power an arduino uno for a long time using batteries. Mostly because the USB feature takes few mA, even in sleep mode. The voltage regulator also needs at least 7V to work normally, a too high voltage for efficient use with batteries. And the last problem is the power green led, also few mA.

With the arduino mobile you can power the board from 1.8V up to 5.5V. There is no USB capability anymore or almost, we will see that in the next steps, no voltage regulator and no power LED.

When in sleep mode, the arduino mobile takes only few uA. It can last months on cells.

The pinout is the same as the arduino uno and the integrated led connected to pin 13 is still there.

Step 1: Let See the Schematic

Power supply must be connected to J1 (1.8V -> 5.5V).

D1 prevents polarity mistakes. But it makes the voltage to drop to 0.6V. If you want no drop, solder SJ1.

The atmega328 should be pre-programmed with the arduino bootloader. You can take it from an arduino uno or program a new micro controller yourself (I'm sure you will find instructables about how to do this).

The FTDI connector is use to insert an USB-Serial device in the purpose of programming the arduino mobile.

I've put an ISP connector in case if you want to program the atmega328 directly, without arduino software.

Few capacitors, a 16Mhz crystal, a LED for pin13 and that's all !!

Step 2: Let Make the Board

I've attached in this instructable the Eagle files of the schematic and the PCB.

I recommend OSH Park to make this board but any other provider should be able to do it.

If you are not familiar with Eagle and PCB making, feel free to contact me. I can send you a PCB.

Step 3: Let Upload Your Software

Insert FTDI Usb-Serial adapter (mind the orientation).

Open your arduino software, choose the correct COM PORT and the arduino uno as the board.

Upload your sketch. I recommend to use the blink sketch to verify all is ok.

NB : The usb-serial adapter is strong enough to power the board, so you do not need external power supply when programming.

Step 4: Experiment Sleep Modes

You must use the sleep modes capabilities of the atmega328 and interrupts to wake it up if you want to use the arduino mobile on a project powered on batteries.

This subject cannot be covered here but you will find multiples documentations and examples on the web about arduino sleep modes and interrupts.

Step 5: Let Power the Board As Stand Alone

Disconnect the FTDI.

Then power the arudino mobile from a battery pack (NiMH, Li-Ion...) from your choice.

Let remember that the volage must be between 1.8V and 5.5V.

Step 6: Future Enhancements

I didn't put a reset push button. It could be nice in a next version.

There is no ON/OFF switch. I will think of it...

Step 7: Order the Board

As I said, if you are not familiar with PCB making, contact me from instructables mailing. Ican make a board and send it to you.

Step 8: BOM

I found all the parts on aliexpress.