328P and NRF24L01+ not running off a coin cell

I have a simple circuit that consists of a 328P, TMP102 and an NRF24L01+ that I would like to have running off a CR2032 coin cell. Right now in low power mode it rests at 23uA and bursts up on occasional transmit. It runs fine when a larger, rechargeable LiPO battery powers it but nothing when the 3V coin cell is powering it.
I've used the IDE to put the Arduino Pro or Pro Mini (3.3V, 8Mhz) w/Atmega328 bootloader into it so maybe the Brownout fuse needs to be changed. My preferred method to install the bootloader and upload code is using the IDE and USBTinyISP.

Miker

Read this to

Probably need to change the lower 3 bits in Extended Fuse Byte per Table 29-17. BODLEVEL Fuse Coding:
111 Brownout disabled
110 1.7 to 2.0V
101 2.5 to 2.9V
100 4.1 to 4.5V

Uno sets them to:
uno.bootloader.extended_fuses=0x05
i.e. 101, 2.5 to 2.9V

Spotless.
The only thing I would like to add is that perhaps you are better changing your clock to 4MHz instead of 8, since 3V or lower voltage is not guaranteed by atmel for operation at 8Mhz. By setting the right fuses you can use the internal RC Oscillator to avoid tampering with the mini components.

I believe at 4MHz you can operate down to 1.8V (or is it 1Mhz? - Double check!)

Serial at 4Mhz goes up to 57600bps.

0miker0:
I have a simple circuit that consists of a 328P, TMP102 and an NRF24L01+ that I would like to have running off a CR2032 coin cell. Right now in low power mode it rests at 23uA and bursts up on occasional transmit. It runs fine when a larger, rechargeable LiPO battery powers it but nothing when the 3V coin cell is powering it.

The "bursts" may be causing brownouts. Make sure you put a large ceramic capacitor across the power.

OTOH .... the NRF24L01+ needs 3.3V so I don't see how you can run it off a CR2032. Plus it needs about 15mA, which is also probably too much for a CR2032. If the bursts are very short the capacitor might let you get away with it but you might need to move to something like a CR2450.

Success!
Disabling brownout by changing the Extended Fuse from 0x05 to 0x07 has fixed the problem. I just checked this morning and it has been running all night on a 3V coin cell without an issue. Adding a larger cap as close the the NRF24L01+ power pins will be an eventual mod but right now it's ok.

Thanks to all for the help,
Mike

0miker0:
Adding a larger cap as close the the NRF24L01+ power pins will be an eventual mod but right now it's ok.

Famous last words...

[quote author=fungus link=topic=260774.msg1842247#msg1842247 ]
...
http://www.ti.com/lit/wp/swra349/swra349.pdf[/quote]
Pretty graphs, and simple formulas, :slight_smile: