I need some pointers please! I have been trying to build a simple temp & humidity sensor which will run for >1month on batteries.
So far I have tried an Adafruit Feather HUZZAH ESP8266 but this has an issue with deep sleep and continues to go into bootloader after a few hours. I have used both a DHT22 and Si7021 but get same issues.
I have also tried a SparkFun Thing ESP8266 but even with deep sleep, the board seems to take too much power to run for anything more than 1-2 days with a 2000mAH LiPo.
My general requirements are:
*) Battery run with charger
*) Battery to last >1month without charge
*) Temp & humidity readings every 1 to 5 minutes depending on battery
*) <£35 total cost
I have looked into using a standard, cheap ESP8266 and the Adafruit HUZZAH ESP8266 breakout but would need to add on options such as the lipo charger etc and not sure this would make things any cheaper than getting a board with everything built in.
Just after some advice from someone who runs a WiFi Arduino successfully of batteries.
Hi Pete, here is my design. They run for about 3 weeks between charges, but then I am using small 10440 size LI-ION batteries (same size as AAA). My sensors take readings every 15 mins. More frequent readings will reduce the battery life. They should last 12-15 weeks on a larger 18650 size battery, which is what I run my Weather Station on.
Great looking project! Just a couple of questions:
*) Are you using a standard AAA battery holder for the 10440 and AA holder for the 18650?
*) It appears as though you are taking temperature, humidity and pressure from separate sensors; are they all controlled via a single Wemos D1 Mini or, as the picture suggests, do you have them separated out between a couple of units per room?
*) Is the enclose bought or 3D printed?
10440 li-ion are the same size as AAA, but 18650 are considerably larger than AA, so you have to buy an 18650 specific holder. You can get AA size li-ion, I can't remember the numeric size code, but their capacities are much less than 18650 size and not that much more than 10440, so I was not impressed enough to try them.
I don't know how much you know about li-ion batteries, but beware of any brand that has the word "fire" or "trust" in it. Don't buy anything that has a claimed capacity that is hugely higher than the more reputable brands. For example those "600 mAh" 10440 batteries have a capacity not much more than half what they claim. If you see any 18650 cells claiming to have capacities of close to 10,000 mAh, don't touch them. They are fake. They contain a much smaller li-ion cell inside a larger outer case packed with filler. Stick to reputable brands, pay the extra.
Yes, I have several separate units around house with one sensor each, mostly sht21 temp/hum sensors, one with a bme280 temp/hum/barometer. My schematic was intended to show that any combination of i2c sensors you wanted could be used in the same unit.