So this is still sitting on the shelf in my kitchen and waking up every 15 minutes to check temp/humidity and battery voltage. Battery was installed as it shipped from Ali Express, 3.3v (LiFeP04) and never charged before or since. That was in April and this is how the battery and frames looks now. I had an admirer reset the Arduino once since the battery went in but it has run continuously since April.
I am tempted to check the cell voltage in case the voltage divider is not right but I actually did this before
Impressive @Charles
Does anybody have the magical incantations to upload the OptiBoot firmware compiled by @Charles on 3.3v Arduino Pro using avrdude?
(Or any other tool which doesnāt require MS Windowsā¦)
Great video and test, the low power consumption is amazing!
What is you preffered way to power those boards?
Lets say youāre using some rechargeable batteries. If using LI-Ion this would mean that a LDO is required which also needs a bit of power all the time (for exmaple the MCP177-33: typical 1.2uA input quiscient current), as the absolute maximum rating for the RFM95 is 3.9V according to its datasheet.
A full Li-Ion battery gives you about 4.15-4.20 volts.
Myself, I would not be too concerned about the differance between a node runing at less than 0.8uA without a regulator, versus circa 2.5uA with a low cost MCP1700 or similar.
Take an example, a node that uses a pack of AA Alkalines to power a node for 5 years. At a capacity of 2800mAhr, the battery goes flat in 5 years doing useful stuff such as reading sensors and doing transmissions. Thats an average of 1.53mAhr per day.
The āgoodā node uses in that 5 years 0.0008 x 24 x 365 x 5 = 35mAhr doing sleep. The ābadā node uses 0.0025 x 24 x 365 x 5 = 109mAhr in sleep.
The difference in mAhr used during sleep, between good node and bad node is 109mAhr - 35mAhr = 74mAhr, or around 50 days extra battery life over the 5 years, big deal.
So no need to follow the crazy advice to operate the LoRa device direct from a LiPo, just use a regulator, it has very little affect on battery life.
If the very small amount of current the regulator uses is somehow significant, and its not in a lot of cases, use a LIFePO4 to power the node. These are safe to use on LoRa devices without a regulator, safer then LiPo bombs too.
If 150mA output is enough, there is the MCP1711, quiescent current of 0.6uA.
I take no credit for the code behind this @everhamme, I am pretty sure I have used all of Charles Hallardās code. The project is his with plenty of support HERE on his GitHub repo and on this thread. I am sure I found a link in the thread to well optimised code which I think he improves further with a lightweight bootloader. Search this thread would be my first hint.
Shows the node based on his PCB in operation with low power numbers.
No, you are correct, that repo is hardware, the PCB that @Charles designed. This thread has all the information you need to get the pcbās, learn a lot about LiPo / LiFePO4 batteries, the voltage tolerance of the Arduino and the RFM95 radio. There is also a ton of information about modding your Arduino by taking the LDO and power LED off the board but if you drill into the posts there is some code and other stuff too!
Charlesās bootloader:
Charlesās PCB
Charlesās post with code, much debug stripped out:
The Adafruit breakboard for the TPL5110 has a trimpot. I find quite difficult to adjust it to get the required delay, at the end soldering a resistor is easier - at least more predictableā¦
The way the TPL5510 is used in this design is just to wake-up the AVR from deep sleep like you would do with an RTC; it does not cut the power. When in deep sleep the ATmega328P retains its state, so it is not a problem to loop on the sleepā¦
