i have a little project with
2 x AA batteries ( 1500mah)
then
a
arduino mini pro 5V /16mhz
A blinking led ( 20ma) Each 2 seconds
A nrf24L01+ in RX mode ( 13,5ma)
now this need to run only 24 hours one time on the 2 batteries
is this possible ,or will i need to change the batteries within 24 hours.
i can not simulate this , so it's direct live working.
arduino mini pro 5V /16mhz
A blinking led ( 20ma) Each 2 seconds
A nrf24L01+ in RX mode ( 13,5ma)
arduino @ 45ma x 24 = 1080
nrf24L01+ @ 13.5ma x 24 = 324
led @ 20ma x 24 = 480 / 2 = 240
I would not count on it.
jackwp:
arduino @ 45mA
I haven't measured one, but a Pro Mini should draw less than that, as it doesn't have on-board USB-to-serial conversion.
Operating a 5V Pro Mini on 3V is a bit sketchy in my book.
Operating a 5V Pro Mini on 3V is a bit sketchy in my book.
OH, yea, I missed that.
I don't have a mini. When I measured my leonardo , it was 45ma. Anyone have a mini and a meter?
What's the project planned to do?
jackwp:
Anyone have a mini and a meter?
I do, not sure I can get to it right away though. SWAG would be 15-20mA at most, I think it's just the MCU and a small power LED.
the project is a sort of lap counter.
if the arduino + nrfl2401 is in the reach of the base station it counts a lap and blink a LED
sketch etc . . . works perfect.
i 'v take 3V because the nrfl2401 works on 3V ,now the mini works also perfect on 3V (Vin) but if i read it wil not run on 16Mhz but little slower.
if i am at home will try to measure the consumption of my mini
When you get to use the meter, also hook the batteries to the board, and check the voltage. 2 alkaline batteries should give you 3.0 volts, while 2 rechargeables may only give you 2.5 volts. So, if I was to guess, I would guess you are using alkaline batteries.
In researching more, looks like the mini pro is designed to require lots less power than my leonardo. Let us know your readings.
Thanks, Jack
helmuteke:
the project is a sort of lap counter.
Depending on how fast the laps are, sleeping could save significant amounts of energy.
i 'v take 3V because the nrfl2401 works on 3V ,now the mini works also perfect on 3V (Vin) but if i read it wil not run on 16Mhz but little slower.
The Arduino Pro Mini 328 - 5V/16MHz runs at 16MHz, period. Lower the supply voltage and it still runs at 16MHz but now is technically overclocked and not in compliance with the data sheet specs. Yes they often work this way, but if and when they don't, there is no one to complain to. There is also a Pro Mini 328 - 3.3V/8MHz that may be more appropriate.
So ,
batterypack = 3.2 V
Arduino mini runs the blink sketch = 7ma - 7.5ma
if i use my setting (arduino + rf) i have values of
22ma if led not blinks
42ma if led blinks
52ma with multiple leds
I think your system will run for 24 hours then!
Good job.
Jack
alright
the only concern i have is running 3v on a 5V board.
but i place the 3V on the Vin and thats normally 3.3V
so what could happen in worst case ???
helmuteke:
so what could happen in worst case ???
Worst case would probably be the processor executes instructions incorrectly, so the program behaves in some unspecified way. I think memory corruption could also occur, which would cause similar symptoms. Finally, I believe the standard brownout detector setting is 2.7V, so once the battery gets to that level the MCU will go into reset, but typically what happens is that once in reset, load is removed from the battery so it recovers some, then the MCU runs some more, so it does this on-off-on-off business.
Does that board have a Vin , or is it Vcc?
what I read, seemed to say that board (maybe a different version of it), can be run at 3.3 volts easily.
On most boards the brownout function of the cpu have been disabled, as I understand it.
Worst case, who knows. I suspect no hardware damage, just did not process all the data you wanted.
jackwp:
Does that board have a Vin , or is it Vcc?
what I read, seemed to say that board (maybe a different version of it), can be run at 3.3 volts easily.
It has a regulator on board. It can be supplied with 5V or with 9-12V, like an Uno. There are two versions, 5V/16MHz and 3.3v/8MHz.
On most boards the brownout function of the cpu have been disabled, as I understand it.
BOD is disabled on raw chips from the factory, but I believe Arduino boards ship with the same fuse settings as in the boards.txt file. 0x05 is the 2.7V setting.
uno.name=Arduino Uno
uno.bootloader.extended_fuses=0x05
pro5v328.name=Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega328
pro5v328.bootloader.extended_fuses=0x05
pro328.name=Arduino Pro or Pro Mini (3.3V, 8 MHz) w/ ATmega328
pro328.bootloader.extended_fuses=0x05
Thanks for the clarification Jack.
Did we decide the OP has the 5 Volt board, or the 3 volt board ?
You bet. Original post says arduino mini pro 5V /16mhz
you can also squeeze some extra power by putting the arduino to sleep for those two seconds. The RX pin could toggle an interrupt to wake the cpu when needed.
i have the 5V board
did already weld 20 devices 
see no direct a solution now
normaly i placed 4x1.5aa battery so i have 6V that would be fine
but the problem is that the nrf24l01 needs 3.3 and the mini doesn't have 3.3v out
you guys have a idea
helmuteke:
i have the 5V boarddid already weld 20 devices
see no direct a solution now
normaly i placed 4x1.5aa battery so i have 6V that would be fine
but the problem is that the nrf24l01 needs 3.3 and the mini doesn't have 3.3v out
you guys have a idea
I'd say the MCP1700 was custom-made for you!
If you want to stay with batteries, use one bank of 4 for arduino, and another set of 2 for the nrf24l01 .