Liion batteries

[BSoft]

@axillent said:

any li-po are rechargeable and their fully charged voltage is about 4.2V
you still can power promini directly but you will need an LDO to power nf24L01

Could we avoid the LDO by using a pro mini digital/analog output set to High/duty cycle=100%? Maybe with a capacitor for ripple suppression!?

Because i think the máx 40mA per output pin could be ok to power source the nRF24L01+.

And whats the inconvenient if we want to use sleep modes?

[axillent]

@BSoft at you own risk you can do whatever you want))
the risk is to lost NRF24L01 which will stop working after supplying a voltage above 3.6

nobody knows how module will be working using PWM output with uncontrolled voltage
I will recommend to use LDO, promini has LDO on board

[BSoft]

Thanks for the reply @axillent

What i want is to minimize power consume removing LDO from equation (and neither adding a more efficient one).

From my understand digital output or analog output (PWM) never gets above 3.3V for an ATMega328p 3.3V, please correct me if i'm wrong.

I'm waiting for the material to run some tests.

My real concern is if ATMega could maintain an output while at sleep, i doubt it.

[BulldogLowell]

@axillent said:

you still can power promini directly but you will need an LDO to power nf24L01

@BSoft , @axillent

If you are powering with 3.3 volts or higher, It seems to me that you use the on-board voltage regulator on the 3.3V ProMini by simply wiring the power supply in to the RAW pin.

This will give radio power at 3.3V, the problem is if your sensor(s) are 5V. Well, in that case it seems that you simply need to keep the input voltage at 5V+ but no higher than 12V.

No?

I am using the 3.3V ProMini exclusively on my wall-wort powered devices that require 5V in this fashion. I find it much easier than stepping down the voltage for the radio. So far, it is working brilliantly, however I wouldn't know the dynamics of how this would affect a battery power supply.

I am (ignorantly) powering my MailBox sensor this way... FYI.

[axillent]

@BSoft PWM is a digital output, not analogue. You can transform it to analogue by applying filter but still it is a bad idea to use this instead of voltage regulator

What is your goal? What do you plan to use as a power source?

[BSoft]

@axillent I want to use a Lipo between 3.35 and 4.2V. For the atmega i could bypass the regulator, but nRF24L01 does not accept above 3.6V, so i have a problem.

So i'm trying to use atmega output that gives me 3.3V.

My primary goal is minor power consume avoiding all types of regulators.

[BSoft]

@BulldogLowell said:

@BSoft , @axillent

If you are powering with 3.3 volts or higher, It seems to me that you use the on-board voltage regulator on the 3.3V ProMini by simply wiring the power supply in to the RAW pin.

This will give radio power at 3.3V, the problem is if your sensor(s) are 5V. Well, in that case it seems that you simply need to keep the input voltage at 5V+ but no higher than 12V.

No?

I am using the 3.3V ProMini exclusively on my wall-wort powered devices that require 5V in this fashion. I find it much easier than stepping down the voltage for the radio. So far, it is working brilliantly, however I wouldn't know the dynamics of how this would affect a battery power supply.

Yes, if you use the pro mini on-board regulator you have 3.3V to atmega and nRF24L01 but at the cost of regulator power consume. If i remind that regulator have an efficiency of 20 or 30%, it's pretty bad.

And yes, you could at the same time use your battery to power 5V devices (bypassing regulator), but since it's unregulated you have to be careful with the drop voltage of your battery (check if that sensor could work between that voltage range).

Yes, using on-board regulator permits battery voltage between 3.35V and 12V... if you bypass regulator, you could supply even lower voltage, but you will have a max frequency limitation.

Please be careful with one thing you said, if a secondary sensor needs 5V you maybe could not connect a battery of 12V to it, you have to check that sensor datasheet.

It is ok if you connect a 12V battery to pro mini RAW pin because there is a regulator on-board that allows you to do that, but could not be the case with a secondary board.

[axillent]

@BSoft OK, I see
Again and again I'm recommending you to use LDO for NRF24
There are modern LDO's who consume just a few uA
Alternatively you can use 2 x 1N4148 in serious, each will hold about 0.5-0.6V, this will save you NRF24

[Dvbit]

@axillent thanks a lot for your answer and patience with a newbie like me...
The Ldo is needed just with rechargeable cr2032?

Thanks

[axillent]

@Dvbit YAW
CR2032 is not rechargeable and it's nominal voltage is 3V.
while you using CR2032 you do not need LDO

rechargeable version of CR2032 is called LIR2032. For LIR2032 you do need LDO

[Dvbit]

Great. Tx

[Dvbit]

Li like lithium ion in my post... Doh

[allanvbcrew]

@axillent "There are modern LDO's who consume just a few uA"
Do you have any reference in mind?
Thanks

[axillent]

@allanvbcrew will recommend XC6206P332MR
you will need just 2 x 1uF ceramic capacitors
it is stated that quiescent current is about 1uA
maximum input voltage is 6V