[TriEmbed] TriEmbed Digest, Vol 80, Issue 10

Wed Jan 8 12:30:47 CST 2020

All,

First, Happy New Year and I hope I can find the time to be more active this
year with TriEmbed.

Dewey,

I have been building and deploying cellular IOT devices in NC parks for the
past couple years and almost all of them are solar powered.

You asked what folks are using for wireless communications.  I was rolling
my own solution for a year or so but eventually decided to use the Particle
platform.  There are a few factors driving this including:
- Global platform - $2.99 / month for cellular connectivity in 150 countries
- Well thought out API including library management.
- Robust remote management and OTA updates makes managing a fleet of
devices as easy as managing one
- Code compatibility across Cellular, WiFi and Mesh
- Very active and helpful community
Probably overkill for your application but worth a look.

I think it is great that you are getting back into electronics (I took a 20
year break) and that you are doing this with your son.  I also found the
folks of TriEmbed ver helpful as I got (re)started in electronics. I would
not have made it this far without their help.

Good luck,

Chip

____________________________________
Chip McClelland
chip at mcclellands.org
919-624-5562

On January 8, 2020 at 11:33:54 AM, triembed-request at triembed.org (
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Today's Topics:

1. Re: wireless communications and battery life (Glen Smith)
2. Re: wireless communications and battery life (Gregg Tracton)
3. Re: wireless communications and battery life (Brian)

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Message: 1
Date: Tue, 7 Jan 2020 22:43:37 -0500
From: Glen Smith <mrglenasmith at gmail.com>
To: Dewey Hylton <plug at hyltown.com>
Cc: Triangle Embedded Computing Discussion <TriEmbed at triembed.org>
Subject: Re: [TriEmbed] wireless communications and battery life
Message-ID:
<CANwtiDVRC8uGN75CbvUoja6tC4F8Zevn=yVLNDEsV8X1ozBC-Q at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

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
>
> _______________________________________________
> Triangle, NC Embedded Computing mailing list
>
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>
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Message: 2
Date: Wed, 8 Jan 2020 07:32:19 -0500
From: Gregg Tracton <tracton at gmail.com>
To: Glen Smith <mrglenasmith at gmail.com>
Cc: Dewey Hylton <plug at hyltown.com>, Triangle Embedded Computing
Discussion <TriEmbed at triembed.org>
Subject: Re: [TriEmbed] wireless communications and battery life
Message-ID:
<CAFP44ZVJ48L1FvwntsRFfDHidvpXsJD2mZYAYPpugRG2RnvdOA at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

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

Use a plastic mailbox. Mine has lasted 30 years, so they are pretty tough.

The camera is a nice idea for telling you how much mail there is, and if
there's a big box delivered that you need to get before package theives get
it. The post office now has a free service where they will send you
pictures of each piece of mail, via email. (I know there's a meta joke in
there somewhere about email eating it's own ancestor...)

You also might consider a passive wifi amplifier. It turns out that a
Pringles can -- the old style that was lined with metal - is a near-perfect
wave form for wifi frequencies, and had been demonstrated to amplify the
signal to a 1-mile range. Don't know about the power requirements, though.

Look into mesh networks instead of wifi. At 250', you'll need
intermediaries, I'm sure. Or a laser point to point system, which needs to
be perfectly aligned but would be really fun. Lasers might have issues in
the rain, but using a reflector at the box and the laser at your home would
solve the power issues since all you'd need is a little piezo speaker to
tilt a mirror in/out of alignment to send a serial signal.

Think about how the cold will affect battery/charging power, and if you'll
need to waterproof the system, even inside the box.

-g

-- 
Gregg Tracton: tired, retired & inappropriately unattired (PJ's)
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Message: 3
Date: Wed, 8 Jan 2020 11:33:41 -0500
From: Brian <triembed at undecidedgames.net>
To: triembed at triembed.org
Subject: Re: [TriEmbed] wireless communications and battery life
Message-ID: <824a915d-b85a-e823-8fea-a770049275c6 at undecidedgames.net>
Content-Type: text/plain; charset=utf-8; format=flowed

On 1/7/20 10:43 PM, Glen Smith via TriEmbed wrote:
> 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

Great idea! And very likely the complete answer to the power question,
since the device will only be awake a tiny fraction of the day, as you
pointed out.

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

Faraday cages aren't very effective when they aren't grounded. If the
mailbox doesn't have continuity to Earth (on a dried-out wooden post,
maybe), it won't attenuate the signal as badly (RF power will still be
lost by induced eddy currents in the metal, but the metal won't be as
reflective as it would be if grounded).

That said, all you really have to do is get the antenna outside the box.
It shouldn't be too hard to find an Arduino-friendly RF module with a
connector (SMA or UFL) instead of an onboard antenna; then a short cable
and "rubber duck" antenna mounted outside the box is all you need.

-B

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End of TriEmbed Digest, Vol 80, Issue 10
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