Can I power my Arduino Mini Pro (5V 16Mhz) direct from motorbike battery?

Hi guys, I've made a little gadget based on Arduino Mini Pro 5V 16MHz and I'd like to power it directly connecting the RAW pin of the Arduino to the positive of my motorbike battery. Is it possible or should I use an adapter? If yes why?

I think the battery could be around 11/12V at engine off and around 14/14,5V while running... if I'm not wrong inside the Mini Pro there is a MIC5205 that can take 16V as max Vin with no problem but I've read that some guys tend to use an external DCDC converter to power the Arduino with a 5V... why?

Thanks! Marco

According to the specs 12V is the upper limit so a charging 12V SLA will most likely see the end of the Mini. Using a voltage regulator will bring the voltage to a safe value (I use 9V to power mine) plus there is less volt drop/heat on the on-board regulator

Sorry but, if I'm not wrong, the spec on both the Mini Pro and MIC5205 say 16VDC as max Vin...

I could not find anything on the 16v...

From the Arduino specs

Power The Arduino Pro Mini can be powered with an FTDI cable or breakout board connected to its six pin header, or with a regulated 3.3V or 5V supply (depending on the model) on the Vcc pin. There is a voltage regulator on board so it can accept voltage up to 12VDC. If you're supplying unregulated power to the board, be sure to connect to the "RAW" pin on not VCC. The power pins are as follows: RAW For supplying a raw voltage to the board. VCC The regulated 3.3 or 5 volt supply. GND Ground pins.

if I'm not wrong, the spec on both the Mini Pro and MIC5205 say 16VDC as max Vin

You are wrong:-

Board Power Supply 3.35 -12 V (3.3V model) or 5 - 12 V (5V model)

from https://www.arduino.cc/en/Main/ArduinoBoardProMini

Their are other things to consider here including the working voltage of the capacitors and most importantly the power dissipation of the MIC5205.

Plus a motor bike is quite an aggressive environment for electronics requiring voltage spike suppression and lots of extra smoothing to make the processor still work when the motor is on.

A two stage drop system sounds best and gives oppertunity to add extra decoupling to the supply.

Not according to these specs - 12V max

ProMini Specs

I found the information both on the Mini Pro schematic and the MIC5205 datasheet:

Yes, spike could be the response why to use an external DCDC

I found the information both on the Mini Pro schematic and the MIC5205 datasheet:

Yes but you fail to appreciate the difference between a component specification and a product specification. So sorry you are wrong you can't connect it directly.

Ok, I'd just like to be sure!

Can you point me to the simpler circuit I can use to power my Mini Pro from my motorcycle battery? There is a lot of circuit on the web but as probably you have understood I'm not expert on HW so your help will be appreciate. :)

Look at this one http://www.researchcell.com/general/7809-pin-and-circuit-diagram/

Grumpy_Mike: Look at this one http://www.researchcell.com/general/7809-pin-and-circuit-diagram/

Great thanks! I've just found this other circuit using 7805: https://www.dropbox.com/s/vt39filqi5lzi8l/12v_pwr_sply.jpg?dl=0

What do you think? Is it better to use the 7809 or 7805 for my purpose?

I'd like to put my gadget in a very small closed plastic case (waterproof will be the best)... what can I use as heatsink if really needed?

The point in dropping it in two goes is that any heat generated is split over the two regulators and you get extra isolation from the main bike’s circuitry.

Thanks guys, I've really appreciate your help!

Grumpy_Mike: Plus a motor bike is quite an aggressive environment for electronics requiring voltage spike suppression and lots of extra smoothing to make the processor still work when the motor is on.

Or, like I've said on other threads: Engines are hell.

Markino, in addition to the protections against conducted spikes, you might also require shielding the device from radiated noise. There was one thread on here where the guy's circuit would malfunction more severely when he moved it closer to his bike, even if it was powered by a stable wall adapter.

Depending on the power required have you considered using one of the car cigarette lighter -> USB adapters?