Hello all ,
I am beginner and i just finish testing from USB
my project on my arduino pro mini 5 volt.
The project has an lcd and runs fine on USB
And the time came that i wanted to test on batteries.
I connected the RAW and GRND of pro mini with batteries and the project didnt run.
(with batteries)
I ve made some experiments .
I tried a simple blink program and the arduino run ok in batteries.
I ve tried again onother .ino with lcd and DIDNT run.
Thankfully i measure the Vcc pin of pro mini when was in battery (8 AA =10volts )
and i discover that VCC has 3.29 Volts.
And thats why lcd not running.
But when i bought Pro mini i bought 5volt version and not 3.3 version.
(as you can see from the image)
And because i am 'bearning' as a beginner and cant wait Monday to go to seller
i am DESPERATELLY asking here if someone knows
a)Is it some hardware failure?
b)Is there some adjustment that i can do ?
c)Or maybe i must try to convice the seller that he gave me 3.3 voilts even if i have receipt that says 'pro mini 5 volt'....to replace it....
d)is it something else?
On the Arduino IDE i have marked Toolls->Processor ->ATmega328P(5 V,16mhz)
Thank you in advance....
It looks to be a CLONE and as they did not seem to mark it as a 3.3V version OR a 5V the seller probably made a mistake in the one he gave you.
If it is a local seller then a simple swap.
If NOT local then some form of exchange by post etc.
You neglected to say what the batteries were and how much voltage and current they can supply ?
Also what else is connected to the board.
A schematic would be worth the effort here ?
Thank you for your answer.
As i ve said ,with the 8 x1.2 v batteries(~10 volt)
the blink scetch is running perfectly.
Just after connect an i2c lcd (A4,A5 SDA ,SCL)(vcc of lcd to vcc on arduino and ...ground to ground)
for a single lcd.print("somthing")...does not run.
Most propably (for my bad luck)...it is the thing you said...(and is local seller)
Just that i was so happy that i finished my project and the only thing remained was to just test for how long the batteries will keep....
...and now....all gone...And Thusday we have mini lock down here in Athens....
You may also want to try to print over the serial monitor the value of F_CPU. If you have a 3.3V regulator, F_CPU should also be 8000000.
What board entry do you select when programming the Pro Mini - 5V or 3.3V?
16 Mhz....
See the image.
Now i am worrying more...
So is 16 Mhz but 3.3 V?
Also...Programmer=AVRISP mkII
Have you measured the Vcc without anything connected to the board? If that's 3.3V, somebody might have put the wrong voltage regulator on it; check the markings on it. The official SparkFun ProMini uses a MIC5205 which will work for both the 5V version and the 3.3.V version.
I would also check the voltage on the Raw pin with everything connected; if that's too low, the voltage regulator will work unreliably or not at all.
Note
You will not have to worry about that you damage anything, only that it does not work 
Now i am relly confused.
Without loads on it and from USB is 4.94 on Vcc
...................and from batteries is 3.3 on Vcc
???
I will come back soon to check it more....
Missed it before, but a ProMini does not have USB; so the power comes from your USB-to-TTL adapter and goes straight into the Vcc (so at the output side of the regulator) and that is what you measure.
Vraw goes through the voltage regulator.
Yes...when i said usb i ment through ftdi.
But is it strange ?
Or do you mean tht from ftdi NOT passing through the regulator
and as so still has 5 volts?
(sorry for my bad lan+gauge in electronics and generall in english)
Now i even change programmer to USBasp
but still same.
No loads ..just a blink scetch and
From ftdi powerd Vcc counts ~5 volt
and from 10 Volt batteries on raw i have 3.3 on vcc...
SpatkFun's official schematic
USB power does not go through the voltage regulator; you've (I assume) connected it to the Vcc pin.
Its not from spark fan
its ....i dont know exactly but it is this...
The "Programmer" choice does not make a difference; you are not Programming thru the SCK/MISO/MOSI pins, and that is the only time that a Programmer would be needed.
If you have ~10V on RAW, and measure 3.3V on VCC, then you probably have a 3.3V/8 MHz Promini.
Can you read any markings on the regulator? It is the part with 5 legs.
The FTDI will connect 5V from USB to VCC, which is connected to the output of the regulator; that is why you measure ~ 5V on VCC when the board is powered from USB.
The 328P chip will run at 8 MHz from 3.3V or from 5V.
The 2 black things !!(because i am an expert on electronics)
saying
a) S4
b)S2RA the regulator
that just now i am seeing in the link that is ....3.3?
So in this case i have a fault 5v Pro mini?
If this Mini still has the original bootloader that was on it when you purchased it, and you have not burned a new bootloader as a "16MHz 328P", then it simply has the wrong voltage regulator installed. Or the seller may have taken a 3.3V 8MHz Pro Mini and burned the 16MHz bootloader to it, which would not be proper.
The 328P will not run reliably at 16 MHz on 3.3V. It needs 5V for that speed. This Mini will work fine as a 3.3V 8MHz Pro Mini, but that would require burning the 8MHz bootloader to it. It will also work fine at 16 MHz if you power it from USB, or from a regulated 5V supply connected to the Vcc pin, bypassing the regulator. It would probably also work with 3 alkaline AA batteries (nominal 4.5V), or four rechargeable AAs (4.8V) connected directly to Vcc (just make sure Vcc doesn't get more than 5.5V).
As i remember it was enclosed in sealed small plastic 'bag'
so i think that the seller didnt override the bootloader.
And ...i cant use it like this because i fixed my first perfboard
to have
a)3 hx711 amplifiers for load beam cell sensors
b)dht
c)sim800l sim card
d)2 relays
....Aaaaaaaah..............1 more steop and i would have finish the project...but what to do?
>:( >:( >:( 
Best way is described in reply #13; 4 batteries (4.8V) to the Vcc pin.
Ok...thank you ALL
Its about 10 euros more from spark fun (not so much)
and at least have the same pinout as i am seeing...
The thing is that i have also order from banggood the same module (with some more tings)
Anyway...
THANK YOU AAAAAAAAALLLLLLL
sterretje:
Best way is described in reply #13; 4 batteries (4.8V) to the Vcc pin.
Do you mean to have an external regulator ?
Because this is for a beehive sacale...on the farm field ...
I need more voltage to stay/keep it alive for some days....
No, you can feed 4.8V from a battery directly into Vcc. That's the same as what you do with the USB power, it goes in the Vcc.
sterretje:
No, you can feed 4.8V from a battery directly into Vcc. That's the same as what you do with the USB power, it goes in the Vcc.
Yes but to do this having 10 volts starting/initial battery voltage
i must use a step down....
That is ..that my hole thinking about using as much less components can be done...it flies away...
I mean..yes this can be doine...but ...it is not the best.
