Arduino 3.3v or 5v

[mathias]

Hi,
Im a little confused what is best to use when building sensors if i should use 3.3v with stepup if needed or 5v arduinos with stepdown to 3.3 for the radio?

Are there any general good guidelines on what to use?

Also if i have some sensors i want to use and there arent anything printed on them if they require 3.3v or 5v are there any way to measure that or do i need to search the web for what it needs?

//Mathias

[rvendrame]

If you use 3.3V arduino, and feed 5V (or even more) to the RAW pin, the on-board regulator will step it down to 3.3V, so you can connect the radio to arduino's GND & VCC pins.

Please note the on-board regulator can not provide too much power. And it looks 12V is the absolute maximum in many board versions (specially in cheap clones). I burned some, by feeding 12V (with some fluctuation) into the RAW pin. Anyway, if you stick to 5V - 9V into RAW, and only powering the radio from 3.3 VCC pin, it should be ok.

If you use 5V arduino, you need to power 5V into VCC (or 7V - 12V into RAW), and you must use a 3.3V step down to the radio.

[RJ_Make]

@mathias I use both, depending on the application. Example: If I'm powering from mains to 5v, I'll use the 3v3 version so I can power the radio off of vcc.

[Sparkman]

@mathias Hi Mathias, are you planning on using battery power or supplying power from a AC power adapter? For battery powered devices, I used the 3.3v ones and typically for the ones powered by an AC adapter, I use the 5V one. For the voltage level of the sensors, if you can't find the spec sheet, try them at 3.3v first and if they don't work there, then try them at 5V. What type of sensors are they.

Cheers
Al

[mathias]

On of the sensor is the distance sensor that looks like Wall-e.

I havent started to test with battery yet but what i read it doesnt sound like you can power a simple sensor for so long with batteries?

//Mathias