I've been running a project of a Nano with dht22 and esp8266 to post to Emonscms. So far the nano has been connected to my laptop via USB in order to read debug data from the serial monitor whilst the esp8266 has its own lipo 3.7v pack but it's only 1100mah so after a couple of days it drains and stops posting.
I want to move it over to stand alone and I have a 18650 3.7V I was thinking of using for the esp8266. I was thinking of powering the Arduino from a usb battery pack for mobile phones.
The 18650 has around 3400mah. The USB battery pack 2200mah so I'm not seeing much improvement this way. The esp alone would last 2x as much maximum which would take it from 2 days to 4.
I have more 18650's I could parallel up, maybe 6 of them but nano's don't run reliably off 3.7V. So I'm guessing the best option would be to use the 18650's for the esp and a wall charger for the nano.
Any suggestions?
I did think of making a voltage divider and using 5v from the walwart for nano and 3v for the esp8266 but I'm not entirely comfortable doing so and letting it run day and night unmonitored.
Why not ditch the Nano altogether and program the sketch into the ESP8266. You might then be able to put the ESP into deep sleep between reading and save even more power.
Marciokoko:
Thanks, that is so cool I just looked into it. I had no idea it's was it's own Mc. Only problem is I don't have a serial cable for programming it.
Also I would need the LS1117-3.3.
I'll give that a try some day.
USB to UART adaptors are cheap to buy. You would need a 3.3V version so get a 5/3.3 switchable version something like this.
MCP1700 is a better 3.3V regulator option for battery use as it has a lot lower Quiescent current than the LS1117-3.3
Do you think the esp8266 without sleep, will consuele les power than nano + esp8266 with sleep?
It seems to me because sleep code on nano only sleeps nano. So with my current setup, even if nano drops from 24mA to 6mA, the setup still draws those 6mA on top of the ~170 mA of the esp8266 = 176mA.
Whereas with just the nano it would still be 170mA. And according to this source I could take it down to about 15mA:
Marciokoko:
Do you think the esp8266 without sleep, will consuele les power than nano + esp8266 with sleep?
Probably not.
Explain exactly what your doing and how often.
I assume your reading and sending the DHT22 data to Emoncms.org but how often are you reading the DHT22 values and how often are you posting them via Wi-Fi?
By turning off the radio and putting the ESP8266 into a deep sleep it can consume < 1mA and then needs < 20mA when powered (without radio) but when you turn on the radio the power usage will jump to about 75mA when not transmitting and spike up to about 350mA when transmitting. Wifi is the main battery killing problem here.
If battery life is the main concern then maybe consider using different type of battery powered transmitter that sends data to a permanent powered receiver that then sends the received data on to Wifi.
I use something like this Adafruit Feather that reads a BME280 every 10 minutes and then transmits the averaged results every 30 minutes to be picked up by one of these that then posts the results over WiFi.
For the feather device it sleeps as much as possible between readings and data sending and I can get over 1 month of battery life using a 600mAh battery like this. Projecting this usage to a 2500mAh 18650 battery should give about 4 months of life.
Now wouldn't the feather be like the esp8266 breakout I have? It still runs by itself, reading and posting data every now and then.im sorry but I don't see where the difference lies. My module is this:
I cannot see your image in the forum but looking at page source I think I found it on google.
That module (ESP-01) is not ideal for deep sleep mode unless your very handy with a soldering iron as you would need to solder a wire between GPIO16 and reset on the chip to allow waking from deep sleep using the internal RTC timer.
A better option might be a stand alone ESP-12 or maybe a Wemos D1 Mini like this. I'm not sure what the sleep/powered current usage of the D1 mini is but I will try and check over the next few days when I'm not working.