Mailbox Project for Newbies

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I’ve finally got around to documenting my “mailbox alert” project. I initially started with an ESP8266, but as you’ll read, that didn’t work so well. So I dug out my trustee Imp003 and was successful. A bit overkill for an Imp003 since I only use a couple of I/O pins, but the WiFi reception is exceptional! Then, I had the issue of using normal LiPo batteries in Minnesota. I learned those will fail in cold Winter temps. So I switched to a LiFePO4 battery, which operates much better at cold temps. I’ll find out how it goes in January.

I left in all of the documentation for the ESP8266 vs Imp003 and the normal LiPo battery vs LiFePO4. It will give newbies a chance to see the similarities and differences. For those concerned about the higher cost of the Imps, remember that you are getting more than just a circuit board. Not only higher quality and performance, but the security and cloud support/IDE as well.

It seems apparent that newer imps (imp005) and such are packed with so many features and complexity. I sure hope that Imp keeps selling the less expensive and more plain Imps, like the imp003. I’m worried that beginners and tinkerers will be pushed out of the Imp world.

Here is the completed project:
https://www.catpin.com/mailalert

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Thanks for the write up - obviously, solar is nice for not needing to ever charge/replace batteries, but the Energizer L91’s are great for extended temperature range use (down to -40C) and very low self discharge. Two of these will run an imp003 just fine, though you’d probably want to bypass the 3v3 regulator on the breakout completely in that case as I think that’s about 40uA of current draw.

I didn’t see a link to your code, but I presume you’re doing a “shallow wake” when checking the sensor (ie not actually making a connection) - that is a pretty power efficient to do things.

The imp005 isn’t complex to use at all - it does have more features, but the same code will run on it. The real successor to the imp003 is the imp004m which is easier to use as it has an on-board antenna so a 2 layer PCB works just fine (like the imp002).