Measuring the firebeetle
Results (unscientific - should have done multiple tests)
So.. on the AZDelivery board I was seeing (at the battery input)
Running current: 130ma
Deep sleep current: 115 μa
Measuring the firebeetle:
Running current: 130ma
Deep sleep: 462μa??????
Im not sure I trust my multimeter - i am inexperienced in measuring currents, and I suspect it breaks the circuit when it goes out of range, which makes it hard to measure micro and milliamps in the same rig.
Trying another way - connecting a 4.7 ohm resister in series with the battery, and measuing the voltage across it, (measured reister = 5.1 ohms)
Running: 660mv so I=V/R = 0.660 / 5.1 = 0.129a which isnt miles out from the 115ma above
Deep sleep: 2mv so I=V/R = 0.002 / 5.1 = 3.921e-4 = 0000.000392
check: it should be 330x out, so the deep sleep should be 0.129 / 330 = same
0.39ma = 390ua
So why is the firebeetle reading almost 4x the other board??? did i measure the other one wrong?
The firebeetle does have a link you can break to remove unneeded stuff while on battery (RGB LED etc). Ive now broken this and will try again:
With low power mode on firebeetle
Running: 132
Sleep: 84ua
Sleep without potential divider: 58ua which is still a lot more than the specs suggest, but its half what i was seeing on the other board,
WIth larger potential divider resistors
Changing out the 75k potential divider resisters for 1M ones - the voltage still seems to be reading OK, but the current draw is now
Wake: 132ma
Deep sleep 59.7ua
Conclusion
I think this is where the journey ends. Apart from designing my own custom board (which I lack the skills and patience for), I cannot go any further,
One more thing to do on this project, which is a rundown test.
Which is going to be a reading every 30s starting from a full charge.
The other one is still running, and is down to 3.76v after between 06 deb 01:00 and now, which is 60 hours.
According to
https://siliconlightworks.com/li-ion-voltage we have used between 10-20% of the battery so far, giving an estimated full life of 300-600 hours on a 500maH battery. (the graph is so flat at this point its hard to see where 3.76v lays. Ive also make a few mistakes and had to re-flash it during development of the easynow components, so this isn't really fair, just back of the envelope stuff here)
So scaling that up to a proper, purchased rather than scrounged 18650,say 5x the capacity (the ones in my proper vape are about 2600maH), I would be expecting to be able to do a reading every 30s for 1500-3000 hours which is about 60-120 days.
Im expecting the firebeetle to last longer.
Im going to charge them both back up, and race them :) (Wago in now in production in my garden measuring the outside temperature, which is why all this started...)
Time will tell if the empirical results match my measurements and calculations. Like I said im very unsure if my measurements above were right, or if my old multimeter is affecting the readings at these low current levels.
The race
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