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Topic: How to powered Pro Mini (Read 21279 times) previous topic - next topic

mpg5_66

Dear
can I use Vcc near A3 as input voltage (in order to connect directly to battery) ? and not by the VCC on FTDI side ???

Best regards

aarg

Have you read the specifications?
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

mpg5_66

Dear
thanks for you response, I'm reading some documents, for example:
https://learn.sparkfun.com/tutorials/using-the-arduino-pro-mini-33v
http://www.dominicdube.com/wp-content/uploads/ProMiniPinout.png

But Read doesn't mean "understand" for me.
Best regards.

CrossRoads

I think if you measure between the two pins, you will find the VCC pins are connected to each other.
So, Yes to your question.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

mpg5_66

Dear CrossRoads,
perfect, Thanks a lot for your response and your time.
Best regards.

msssltd

VCC is the output of the on-board Voltage regulator. You should only (ever) connect a regulated supply Voltage to VCC; 5V for a 5V board (3.3V for a 3.3V board). 

To power a Pro Mini directly from a battery, you should connect the battery +V to the RAW pin.  The RAW pin is the input to the on-board regulator.  You can connect up to 12V to the RAW pin and VCC will remain at a constant voltage, until the input Voltage falls below VCC + the regulator drop out voltage.

For example, if you connected a 9V (PP3) battery to the RAW pin on a 5V Pro Mini.  VCC would remain at 5V until the battery discharged to 5.7V.  As the Voltage drops further, the Pro becomes increasingly erratic.


septillion

If you have a high voltage battery then yes, connect it it raw.

But a Pro Mini will just work fine on a 4,8V LipPo or something and you want to connect it to Vcc (even a 3,3V Pro Mini, this will only still run @ 8Mhz). The 5V is no must.
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

aarg

Dear
thanks for you response, I'm reading some documents, for example:
https://learn.sparkfun.com/tutorials/using-the-arduino-pro-mini-33v
http://www.dominicdube.com/wp-content/uploads/ProMiniPinout.png

But Read doesn't mean "understand" for me.
Best regards.
Cool. In time, it will.
  ... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

Paul__B

I think if you measure between the two pins, you will find the VCC pins are connected to each other.
So, Yes to your question.
As they should be - it would be very misleading otherwise.

The reason for the duplication is the function of the two rows of terminals.  The (long) side rows are for interface to the application which the MCU is to control while the end row is for the programming and serial communications interface.

Both may be used together, but it is appropriate to replicate Vcc so that either can conveniently be used on its own.  You will note that RXI and TXO are replicated for the same reason and it is always useful to have a number of ground terminations (four in this case).

msssltd

#9
Oct 22, 2015, 02:37 pm Last Edit: Oct 22, 2015, 02:38 pm by MattS-UK
If you have a high voltage battery then yes, connect it it raw.
When is a high voltage battery not a high voltage battery?  When it is fully discharged (!)
A battery is a variable voltage, unregulated, power supply.

Quote
But a Pro Mini will just work fine on a 4,8V LipPo or something and you want to connect it to Vcc (even a 3,3V Pro Mini, this will only still run @ 8Mhz). The 5V is no must.
There is no such thing as a 4.8V LiPo.  A single Lithium Polymer cell is considered safe to charge between 3.0V and 4.2V, with the nominal charge being 3.7V.  The consequence of operating LiPo cells beyond their specifications being a significant risk of unpredictable combustion or explosion.  I would think powering a digital circuit directly from a LiPo, without some form of regulation and conditioning, a very poor design.

However, the documentation is very clear; see the paragraph titled power.

"
The power pins [of a Pro Mini] are as follows:

    RAW. For supplying a raw voltage to the board.
    VCC. The regulated 3.3 or 5 volt supply.
    GND. Ground pins.
"

So.  Whilst you could hook a LiPo directly to VCC and it may work, apparently 'just fine.' It is not what you should do.


CrossRoads

Running a 3.3V Promini with LiPo to VCC pin will work just fine.
You may want to add a part like MAX1811 to provide for battery charge control from USB supply.
http://www.mouser.com/ds/2/256/MAX1811-96760.pdf
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

septillion

When is a high voltage battery not a high voltage battery?  When it is fully discharged (!)
Alright, a "high voltage battery" is a battery that fully charged is higher then 5,5V

A battery is a variable voltage, unregulated, power supply.
It unregulated, yes. But it's very very clean ;) Nothing wrong with connection it to a uC. Like every remote etc in your house will it this way.

There is no such thing as a 4.8V LiPo.  
Yeay yeay, it was just an example. But still, the 4,2V of a LiPo is perfectly fine to drive the Pro Mini direct to Vcc. The 8Mhz (also called 3,3V) version will run within spec to as low as 2,25V so the whol LiPo range. The 16Mhz (5V) version to 3,78V so roughly until have the capacity of a Lipo. You can find the specs in the ATmega328p datasheet, page 303 figure 29-1 ;)

I would think powering a digital circuit directly from a LiPo, without some form of regulation and conditioning, a very poor design.
Then think again ;)

However, the documentation is very clear; see the paragraph titled power.
Yep, but your interpretation is not ;) They are talking about the the Vcc pin will supply (so output) 5V or 3,3V from the on-board regulator when a supply is connected to RAW. And yeay, they don't say anything about supplying the Pro Mini via this pin. But you can just look at the schematic, it goes straight to Vcc of the ATmega328p so that datasheet applies.

So. Whilst you could hook a LiPo directly to VCC and it may work, apparently 'just fine.' It is not what you should do.
Yep you can, and you're totally in spec ;) So it will work fine. So why not?
Use fricking code tags!!!!
I want x => I would like x, I need help => I would like help, Need fast => Go and pay someone to do the job...

NEW Library to make fading leds a piece of cake
https://github.com/septillion-git/FadeLed

msssltd

#12
Oct 26, 2015, 06:04 pm Last Edit: Oct 26, 2015, 06:05 pm by MattS-UK
It [a battery, is] unregulated, yes. But it's very very clean ;) Nothing wrong with connection it to a uC. Like every remote etc in your house will it this way.
Actually, no.  Almost all the remotes in my house contain an ASIC, drawing < 3mA at < 3V.  I also have a so called "smart" remote, which contains an NXP micro controller, drawing 10s of mA from > 3.5V, with a discrete (3.3V) regulator on the PCB.

Quote
Yeay yeay, it was just an example.
It was an example of you getting significant details wrong.  Don't worry, I get details wrong too.  But what I do not do is try to diminish my mistakes.  No.  I apologise (to the readers) for my error and often thank the person who corrected me ;)

Quote
But still, the 4,2V of a LiPo is perfectly fine to drive the Pro Mini direct to Vcc.
By connecting a fully charged LiPo to VCC in a 3.3V (LVTTL)  circuit, you risk causing permanent damage to;
i) Those 3.3V peripherals, which tolerate a maximum of 3.6V on their I/O pins.
ii) Those 3.3V devices which tolerate 3.6V max on their VCC pin.
iii) Those 3.3V devices which tolerate 5V TTL I/O, only when they are powered on.

Quote
The 8Mhz (also called 3,3V) version will run within spec to as low as 2,25V so the whol LiPo range.
Regardless of being 8Mhz or 16Mhz, a ProMini continues to draw mAs of current down to and below 1.2V.  A LiPo cell connected directly to RAW or VCC can become discharged well below the 3.0V regarded as safe to recharge.

Quote
Yep, but your interpretation is not ;)
English is my first language and I do not need to interpret it.  The words say exactly what they mean.

"VCC. The regulated 3.3 or 5 volt supply."

VCC is a reference voltage.   The implication of VCC being a reference voltage is, variable voltage sources connected to VCC, should be regulated.  When the variable voltage source is a LiPo, you should also protect the cell/s from discharging below the safe limit (3.0V).

I'm going to leave it there.  If you don't think it is preferable to design your circuits such that they can not blow up peripherals and turn batteries into fire hazards, we will have to agree to differ.


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