Advice needed: Battery powered remote mailbox notifcation sensor

Dear community,

I need your help in bringing my first real world project alive: a battery powered remote mailbox sensor.

I want to know the feasibility of such a project and especially how you would implement it (and which sensors you would use).

Side notes:

  • Low power consumption -> board selection: I was thinking about Arduino Pro Mini 3.3V + nRF24 radio or Sparkfun ESP8266 Thingy. I am very much open to your suggestions on these, maybe ESP32?

  • I know the postman's delivery time e.g. from 10:00 to 14:00 - meaning the board can sleep most of the time, and listen for the trigger in specified timeframe

  • I was thinking about a reed switch, tilt sensor, motion sensor, LDR(?) - an interrupt would wake up the board and send an alert (execute its part to do so)

  • preferred communication would be via radio to an OnionOmega2 which would send an email of the notification (if using radio comm.), or if this isnt feasable then use Sparkfun Thingy only to send email immediately over the board, or other ESP32 device(?)

  • the distance of the mailbox to the sensor is less than 20meters. also the wifi would be able to reach the sensor inside the mailbox

So right now I'm pondering which sensor and what kind of circuit would be the best (in terms of energy efficiency). I am a beginner and I cant come up with brilliant transistor usages or sensor to reset wiring (if you would consider these) so I look forward to your input which would mean a lot to me.

Here is a link which brought me to considering the sparkfun thingy:

You have not told us the distance over which the wireless must operate.

Have a look at Nick Gammon's low power tutorial


I would use a "bare bones" Arduino, probably one made by removing the regulator from a $2 eBay Pro Mini (3.3V version). That would run for years on 2xAA batteries.

Start by carefully studying this outstanding tutorial on low power operation.

Thank you both for the same link :smiley:

Any thoughts about the sensor to use and a possible circuit diagram?


Do your homework first.

You need to learn to read switches (possibly with debouncing), how low power operation works, how the radio works, each separately, all in good time.

Thank you both for the same link :smiley:

Any thoughts about the sensor to use and a possible circuit diagram?


You'll want to Google 'Arduino mailbox'.
This has been attempted before.

See if any of the projects is useful to you.