Low power wireless sensor node, using stock arduino

Hi ardu-people,
There are a lot of posts in the Internet about making a low power arduino projects. However most of them assume you have to do it with custom built arduinos using atmega chips, I think it’s a correct approach, BUT it is still possible to do a low power node even on stock parts. Below are some hacks I discovered or confirmed while creating my low power projects.

• LED lights
  There are a lot of articles about how much power do they really consume and I can only confirm that, even this tiny power led on your Pro Mini or Nano. I used sharp knife to cut the connection to the power led on my Pro Mini and I desoldered leds on all other peripherals such as radio power converter
• Power down mode
  For my arduino I was using Narcoleptic library, and PowerDown mode for the nrf24l01 radio. For arduino everything worked perfectly, for radio see below
• Cut power to peripheral devices
  To save some more power we can disable sensors while arduino and radio are sleeping, simple solution is to power up sensors using arduino pins, set pin to HIGH to enable device, LOW to power it down, this worked perfectly for me. If you see issues with measurements, you may need to add a delay after powering a sensor up. More appropriate solution is to use tip120 or something similar to disable/enable power for all sensors at once.
• Radio nrf24l01 power down issues
  Unfortunately looks like Nfr chip doesn’t like power manipulations, after several cycles of powering it down with arduino pin as a power source as per above while radio is in the powerdown mode, the radio developed some kind of a power leak and started to consume more (~6ma). Radio is functioning properly, but consuming a lot for a sleep period. I’ve understood that it’s consuming power via MOSI line (pin11), the solution was to set all nrf pins to low and to switch MOSI pin to input mode, don’t forget to switch it back to output when powering everything back up.

Stay tuned, I’ll be working with reducing power consumption with relays, coz they are eating a LOT

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