[TriEmbed] wireless communications and battery life

[Glen Smith]

I'll add my welcome to Brian's, and add a +1 to most everything he said.

The only additional insight I hope to add would be that you may very well
be able to add a small solar cell to the top of your mailbox that will
provide all the power that you need. Assuming that your mailbox has some
solar exposure, even for part of the day. A mailbox sized solar cell like
this:
https://www.amazon.com/Coleman-CL-100-1-5-Watt-15-Volt-Battery/dp/B000CPA670/ref=sr_1_26?keywords=coleman+solar&qid=1578454466&sr=8-26
should
be able to keep a couple of Lithium Ion batteries topped up for a twice a
day transmission of a photograph to the house. As Brian pointed out, this
device need not constantly check anything. the only thing that is important
is an interrupt generated by the door opening. your device wakes up,
establishes a Wi-Fi connection, snaps a picture, transmits it and then goes
to sleep, not to be woken up again until you empty the mailbox.

You biggest problem may be transmitting through the Faraday cage of the
mailbox.

Glen

On Tue, Jan 7, 2020 at 12:24 PM Dewey Hylton via TriEmbed <
triembed at triembed.org> wrote:

> Hello, first post to the list. I'm somewhat new to the embedded space,
> having
> leveraged rpi/beaglebone type hardware for 1-wire projects and such. But I
> am
> just starting to look at lower power devices such as omega2 and arduino.
>
> Quick introduction, and not so quick questions for those with experience
> ...
>
> Several decades ago I was an advanced electronics tech in the US Navy,
> trained
> to troubleshoot/repair nuclear instrumentation and control circuitry. Yup,
> I
> was a subsurface "nuke" and operated the reactor plant on 3 different
> classes
> of submarine ... I was no stranger to the soldering iron and could build a
> basic calculator from simple components (no chips).
>
> But that was a long time ago, and my only real experience with soldering on
> digital equipment is mostly limited to doing so on my Commodore 64 computer
> and peripherals. Also not exactly a recent thing.
>
> Now that I have a 13-year-old boy expressing interest in these things, I
> plan
> to get into the embedded stuff so we can work on some neat (and safe!)
> projects
> together. One idea we came up with was a (USPS) mailbox monitor. I have
> since
> found others doing the same thing online, but we have questions and I
> figured
> this might be a good place to ask ...
>
> The original intent was to monitor the mailbox. Could use a physical switch
> to determine when the door was opened/closed, or even a light sensor to do
> the same. But we wanted to wait a number of seconds after the event, take a
> picture of the inside of the box, and send the results via email or mms or
> whatever. So not only a fun project for us, but something actually useful
> in
> that we could tell whether a package was present or just more bills. :)
>
> Two basic questions, really. The first has to do with power and battery
> life,
> and the second having to do with wireless communications.
>
> We started with the Onion Omega2 because (1) very user friendly, as it runs
> linux and I can use my python/shell/whatever prowess to get things done.
> And
> (2) it has built-in wifi. We are comfortable with this and have done a few
> neat
> things inside the house. BUT ... I think it's going to be quite power
> hungry
> and may rule it out as far as locating in the mailbox and not having to
> change
> batteries every day or two.
>
> About the wireless bit ... I have plenty of experience with "standard" ip
> based networking and wifi, but wonder if that is the best fit here. For
> starters
> my mailbox is about 250 feet from the house. And I figure anything capable
> of
> doing an ip stack over wifi may present similar battery problems. So I am
> starting to look into other communications which are not ip based as well.
>
> We recently had our home alarm system upgraded to include wireless sensors.
> I learned that not only are these devices able to communicate over fairly
> long
> distances (and through walls/brick/etc.) but their tiny little batteries
> can
> last 3-5 years even with the sensors having a mostly constant connection
> to the
> system. Learning this gave me hope that the mailbox monitor might actually
> be
> feasible.
>
> I have found some wireless modules used to communicate between arduino
> units;
> perhaps the mailbox unit can communicate with a much closer unit, and the
> closer
> unit can be fed power from the house and do the smarter stuff while the
> remote
> unit essentially stays asleep until triggered by light or physical switch
> in
> order to conserve battery.
>
> So ... first steps first ... do any of you have experience with low power
> wireless communication which might actually work in my case? Both the
> distance
> and battery life are the main worries currently.
>
> If you've made it this far, thanks for your attention and consideration. I
> look
> forward to hearing some opinions and experiences in this space, and using
> your
> input for projects with my son.
>
> Dewey Hylton
>
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