4 ms·

Thanks, this is interesting. Seems like it would be quite cheap to cobble together an ESP32 + cheap sensor. How would you power it - battery or solar? Any estim

Thanks, this is interesting. Seems like it would be quite cheap to cobble together an ESP32 + cheap sensor. How would you power it - battery or solar? Any estimates of battery runtimes I could get if it woke up every 4 hours or so?

striking 6y ago
If you water your plants by hand, swapping a battery isn't too big a deal. Solar might work if your plant is consistently in direct sunlight, but you need to keep some amount of charge to keep at least the RTC running so that's a hurdle you'll have to ponder. I don't have any estimates of battery runtime or anything, but I'll note that WiFi is battery-expensive and takes a few seconds to actually connect to the desired network so you'll want to wake WiFi as little as possible. Meanwhile, actually doing sensor readings can be done pretty often. So it's entirely feasible that you might do a bunch of sensor readings and then upload them all in one go to save power. From there on out it's a question of how much power a sensor draws, how much power the device draws, and how often you want to wake it.
- olixr 6y ago
  I have been messing around with this a lot. With a pretty bare esp32 no leds and taking a soil reading every 5 mins (and sent via wifi) I have got 1-2 weeks runtime on a 1000mah battery. Reducing wifi and read intervals greatly increases life. You then add in recharging and get much longer runtimes. Ive gotten away with as small as a 6v solar panel 3.5W to keep a box online for 6 months solid.
UncleEntity 6y ago
I have a couple Govee temp/humidity sensors which send out the data as a bluetooth low energy advertising packet -- which anyone can read -- and from what I can tell two AAA batteries should last a year or two. They send out the advertising packet around every 10 seconds so 'low energy' is an accurate naming it seems. Mostly got them to learn about bluetooth and wrote (half a) daemon to log the packets, currently it just prints the data to cout.

striking 6y ago

If you water your plants by hand, swapping a battery isn't too big a deal. Solar might work if your plant is consistently in direct sunlight, but you need to keep some amount of charge to keep at least the RTC running so that's a hurdle you'll have to ponder. I don't have any estimates of battery runtime or anything, but I'll note that WiFi is battery-expensive and takes a few seconds to actually connect to the desired network so you'll want to wake WiFi as little as possible. Meanwhile, actually doing sensor readings can be done pretty often. So it's entirely feasible that you might do a bunch of sensor readings and then upload them all in one go to save power. From there on out it's a question of how much power a sensor draws, how much power the device draws, and how often you want to wake it.

olixr 6y ago
I have been messing around with this a lot. With a pretty bare esp32 no leds and taking a soil reading every 5 mins (and sent via wifi) I have got 1-2 weeks runtime on a 1000mah battery. Reducing wifi and read intervals greatly increases life. You then add in recharging and get much longer runtimes. Ive gotten away with as small as a 6v solar panel 3.5W to keep a box online for 6 months solid.

UncleEntity 6y ago

I have a couple Govee temp/humidity sensors which send out the data as a bluetooth low energy advertising packet -- which anyone can read -- and from what I can tell two AAA batteries should last a year or two. They send out the advertising packet around every 10 seconds so 'low energy' is an accurate naming it seems. Mostly got them to learn about bluetooth and wrote (half a) daemon to log the packets, currently it just prints the data to cout.