Arduino pro Mini 9v battey -> 5V output ?

Hey all,

Newbie question here: I will be using an arduino pro mini 5V powered with a 9V battery.
I'm making an LED chaser, so there will be LED only (around 30).
As I'm about to order the LEDS SMD and the resistors I need to determine the resistors value, and here comes my question:

I found the technical specs which state the arduino pro mini can be powered from 5V to 12V through the RAW pin as there is a voltage regulator, so if I use a 9V battery the output will still be 5V out of I/O pins ?

(so basicaly do I use 5 or 9V to calculate my resistance value)

Thanks !

Yes, the output will still be 5V at the pins.
Use 5V to calculate the resistance values, now that that question has been answered.

How long do you expect to supply 30 LED's with power using a 9V battery?

Let me point out that you may get 300mAh from a 9V battery. As example: 9V Duracell Alkaline Battery Tests -.

With one red LED you'll want to limit the current to 30mA, which can be said then that the LED will draw 30mA X 30 red LEDs + power for the MCU. You might be starting to realize that by using the old copper top battery, you'll not get much operation time.

Something to consider.

Oh, here is an LED resistor calculator thingy LED Resistor Calculator.

Is this a school project? Several questions being quite the same.

Idahowalker:
Yes, the output will still be 5V at the pins.
Use 5V to calculate the resistance values, now that that question has been answered.

How long do you expect to supply 30 LED's with power using a 9V battery?

Let me point out that you may get 3mAh from a 9V battery. As example: 9V Duracell Alkaline Battery Tests -.

With one red LED you'll want to limit the current to 30mA, which can be said then that the LED will draw 30mA X 30 red LEDs + power for the MCU. You might be starting to realize that by using the old copper top battery, you'll not get much operation time.

Something to consider.

Oh, here is an LED resistor calculator thingy LED Resistor Calculator.

Thank you very much for your quick reply !
I will limit the current to around 2ma per LEDS, so it should be fine ! thanks for the links !

Railroader:
Is this a school project? Several questions being quite the same.

Nope, i'm just a hobbyist trying to add leds into a diecast vehicle !

Idahowalker:
Let me point out that you may get 3mAh from a 9V battery. As example: 9V Duracell Alkaline Battery Tests.

That example test yielded 311 mAh.

aarg:
That example test yielded 311 mAh.

Cool.

nordi:
I found the technical specs which state the arduino pro mini can be powered from 5V to 12V through the RAW pin as there is a voltage regulator, so if I use a 9V battery the output will still be 5V out of I/O pins ?

Unfortunately, very misleading.

Do not attempt to use the "RAW" pin for serious projects.

A 9 V battery is inappropriate, especially if it is one of this type:

Use a 4.5 V battery - three "AA" cells in a carrier, connected to the "5V" pin.

Then you can run quite a few LEDs.

Hang on!

The Pro Mini has 20 available I/O pins and those will be limited to about 200 mA in total or 10 mA per pin.

Exactly how do you propose to connect 30 LEDs? :astonished:

Or 4 NiMH rechargeable "AA" or "AAA". (But not 4 non-rechageable.)

Paul__B:
Unfortunately, very misleading.

Do not attempt to use the "RAW" pin for serious projects.

A 9 V battery is inappropriate, especially if it is one of this type:

Use a 4.5 V battery - three "AA" cells in a carrier, connected to the "5V" pin.

Then you can run quite a few LEDs.

Hang on!

The Pro Mini has 20 available I/O pins and those will be limited to about 200 mA in total or 10 mA per pin.

Exactly how do you propose to connect 30 LEDs? :astonished:

Sorry for the late reply, and thanks for the advice:
Unfortunately because of space constraints I would either have to use the 9V battery you referred to, or a 3.7V lipo battery (but then I'd have to also add a 5V booster which is the reason i was going with the 9V battery to save both space and money).
As for being able to run 30 Leds from a mini pro: I will have up to 4 Leds soldered to a pin (some pins will have up to 4 leds, others only 2 leds). AND I will use a 900ohms resistance for each Led. the project only runs LED nothing else.

Charlieplex.

And what battery to use - my view is it's all relative to what you want to do and how long that's supposed to go for.

Could you not fit three "AAA" cells?