ESP8266 Community Forum

- Tue Jun 30, 2015 12:08 pm #22068 hi all,

Im looking at some low power usecases and trying to decide between using a traditional arduino & a RF chip like a (RFM69HW) or the nice ESP8266

Im primarily concerned with power consumption.. (looking at power consumptions using wiki/doku.php?id=esp8266_power_usage) and other sources for Mega328P

My initial usecase is to have a ESP8266 on each house window and check to see if the window is closed when the alarm is set.. If a window is open then send a push notification to my phone to warm me..

Each window has a ESP8266+Reed Switch
Central controller , probably a RaspberryPI

Ideally
- When the alarm is set, a Raspberry PI detects this and then polls each window sensor and asks for its status (open/closed). if any windows are open then send a push notification (pushbullet) to my phone to warn me

Problem
- That means keeping all the Window ESP8266s powered up.. and listening thus consuming ~60mA ... (or is the 60mA only when it receives a packet destined for it?)
Alternative
- Install a MQTT Server (Mosquitto) on my RaspberryPi
- Every minute each ESP8266 wakes from deepsleep (10uA), connects to WIFI and sends a status packet ONLY if the status has changed. this would mean I could power up in wifi down mode and only power up wifi if the status changes.. Power consumption is therefore minimial (???not sure how much??) unless the window state changed
- When the alarm is set then the PI checks the status of each window (from a cached list of last listened states) and actions accordingly..
- Each ESP8266 will probably need to periodically send the status (regardless of if it changes) so that the central PI gets a heartBeat..

Does this sound like a good plan??
Would the arduino be better in this scenario?

- Tue Jun 30, 2015 2:59 pm #22080 There are sleep modes available for the ESP besides deep sleep. In "light sleep" the ESP will maintain a connection with your AP and only consume about 1.8mA (or less).
See http://bbs.espressif.com/viewtopic.php?f=21&t=645
If I read the datasheet for the RFM69HW correctly, the radio alone would consume 16mA if it needs be in RX mode all the time, so the ESP would actually consume less power in this scenario (and that's not even counting the AVR).

However 1.8mA is still pretty high for battery powered applications. With a 2000mAh battery, you would need to change/recharge the battery of each sensor module about every 45days. With 5 sensors or so, I would probably get annoyed real soon...

The deep sleep approach is therefor a much better idea, imho.

- Tue Jun 30, 2015 3:48 pm #22084

The deep sleep approach is therefor a much better idea, imho.

1.8mA is for esp8266 sleeping chip only.
Memory chip on board is consuming lot more.

- Tue Jun 30, 2015 4:17 pm #22087 What about powering them via a solar panel in combination with a rechargeable battery? Just an idea, never did that yet but really would like to since my temp measurement ESP is about to die after 8 weeks (has zero WAF).