Author Topic: Tiny TH Mote  (Read 12052 times)

TomWS

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Tiny TH Mote
« on: August 25, 2015, 04:47:16 PM »
Well, after all the work that joelucid has done perfecting ListenMode and convincing me that we could, in fact, run for a significant amount of time using CR2032 batteries (see thread https://lowpowerlab.com/forum/index.php/topic,1136.0.html), I've finally got my Tiny TH Mote operational.  This runs from a single CR2032 battery with an overall diameter of just 26 mm.  The device is layered with ATMega328P and Si7021 TH monitor on one side, the RFM69W radio on the reverse side, and then, stacked behind the radio, is the CR2032 battery, for an overall thickness of slightly less than 13mm.

I'll be posting the design files, some code, referencing the new RFM69_ATC library, and showing how I intend to package this cute little thing.  I'll also track battery life data here.  Meanwhile, just to show that it exists, here are a couple of photos...  The second one is the pogo pin board I use to do initial program load into the device.

Enjoy!

Tom
UPDATED: 9/11/15 Added Eagle Design Files.  The only change from the original files is that I increased the size of the pogo-pin holes to accept the pins themselves and make a larger target for the probe.

« Last Edit: September 11, 2015, 05:07:32 PM by TomWS »

joelucid

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Re: Tiny TH Mote
« Reply #1 on: August 25, 2015, 06:49:09 PM »
Looks great! Can't wait for my boards to arrive. I need to send you a copy of the bootloader so you don't need to mess with pogo pins ;)

TomWS

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Re: Tiny TH Mote
« Reply #2 on: August 25, 2015, 08:58:48 PM »
Looks great! Can't wait for my boards to arrive. I need to send you a copy of the bootloader so you don't need to mess with pogo pins ;)
Yes you do!  Been waiting for that...

T

Felix

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Re: Tiny TH Mote
« Reply #3 on: August 25, 2015, 09:43:05 PM »
Nice, if you guys use W then you could just use CW radios which have the RFM12b pinout, and it's 16x16mm instead of 16x19mm.
But I don't carry those :P

TomWS

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Re: Tiny TH Mote
« Reply #4 on: August 25, 2015, 10:08:22 PM »
Nice, if you guys use W then you could just use CW radios which have the RFM12b pinout, and it's 16x16mm instead of 16x19mm.
But I don't carry those :P
Good point!  I hadn't thought of that!  Too bad CR's don't come in 16s...  (UPDATE 2015-08-26 18:13:00: removed goofy comment WRT this being a bad suggestion)

Tom
« Last Edit: August 26, 2015, 06:13:51 PM by TomWS »

gregcope

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Re: Tiny TH Mote
« Reply #5 on: August 26, 2015, 02:57:35 AM »
Lovely little beauty...

joelucid

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Re: Tiny TH Mote
« Reply #6 on: August 26, 2015, 12:57:24 PM »
According to the data sheet it does have listen mode. Isn't this just the same module in another form factor? This could definitely shave off a few millimeters if we use cr2032 with pins and no battery holders.

TomWS

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Re: Tiny TH Mote
« Reply #7 on: August 26, 2015, 06:11:16 PM »
According to the data sheet it does have listen mode. Isn't this just the same module in another form factor? This could definitely shave off a few millimeters if we use cr2032 with pins and no battery holders.
Boy, I don't know what I was looking at when I made the comment (maybe RFM12 datasheet?) but I totally messed up on this one.  My apologies to Felix, yes, this is a good suggestion.  I'm going back to modify my previous post.

Tom

luisr320

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Re: Tiny TH Mote
« Reply #8 on: August 27, 2015, 05:37:48 AM »
Just shut up and take my money!  :)
Where and when will these be available?
If they came with a wireless loading sketch in them, it would be a turnkey solution: get them out of the box, connect the battery, load your new sketch wirelessly and you are all set up and ready to use them.
And how about inserting some kind of probes or prongs and make them soil moister sensors? That would be also very neat.

joelucid

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Re: Tiny TH Mote
« Reply #9 on: August 27, 2015, 07:08:49 AM »
Quote
And how about inserting some kind of probes or prongs and make them soil moister sensors? That would be also very neat.

Luisr, that's exactly why my design (2.5cm square) while not quite as elegant as Tom's has 18 connectors on the side to enable custom projects. And yes, the preinstalled wireless bootloader really helps since you don't need to connect any wires to program it. Either put a CR2540 coin cell on top for 540mAh of capacity (that's about the same as a 9V battery!!!), or use it with 2x aaa or aa lithium if you need even more power for sensors.

TomWS

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Re: Tiny TH Mote
« Reply #10 on: August 27, 2015, 08:59:21 AM »
Either put a CR2540 coin cell on top for 540mAh of capacity (that's about the same as a 9V battery!!!)
Except that, with the CR2540, you get to USE almost all of the 540mAH.  You only get to use 1/3 of the 9V battery's...

Tom

joelucid

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Re: Tiny TH Mote
« Reply #11 on: August 27, 2015, 10:11:03 AM »
Quote
Except that, with the CR2540, you get to USE almost all of the 540mAH.  You only get to use 1/3 of the 9V battery's...

Actually you do get all of the mAh out of the 9V battery - but 2/3rds of the energy heats the room via the voltage regulator. In addition to the higher energy density of lithium batteries that's the reason why the CR2540 can be so much smaller while providing the same battery life.

TomWS

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Re: Tiny TH Mote
« Reply #12 on: August 27, 2015, 10:23:10 AM »
but 2/3rds of the energy heats the room via the voltage regulator.
I suppose, where you live, heating the room is useful   ;D
I should add that that's probably true for Felix as well...
T

luisr320

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Re: Tiny TH Mote
« Reply #13 on: August 27, 2015, 10:30:16 AM »
Quote
And how about inserting some kind of probes or prongs and make them soil moister sensors? That would be also very neat.

Luisr, that's exactly why my design (2.5cm square) while not quite as elegant as Tom's has 18 connectors on the side to enable custom projects. And yes, the preinstalled wireless bootloader really helps since you don't need to connect any wires to program it. Either put a CR2540 coin cell on top for 540mAh of capacity (that's about the same as a 9V battery!!!), or use it with 2x aaa or aa lithium if you need even more power for sensors.

Looks like an opportunity to join efforts and create something Greater than the parts  :). And Felix already have a neat store to sell them. I would buy a lot of them.

Felix

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Re: Tiny TH Mote
« Reply #14 on: August 27, 2015, 11:12:26 AM »
Interesting to say the least :)
I would propose going to the 5x5mm 32-MLF or 4x4mm 28-MLF package. That would leave room for other things or perhaps add FLASH memory for wireless programming :)
I would be curious how well a CR battery can handle the burst transmission required by wireless programming though :P
Probably not extremely well, but transmit power could be decreased and hence shorten range of WP to help the battery. The gain is wireless programming when these sit on top of your house, so maybe worth the effort.

joelucid

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Re: Tiny TH Mote
« Reply #15 on: August 27, 2015, 11:15:29 AM »
Quote
I suppose, where you live, heating the room is useful   ;D

Absolutely! That's why I like the si7021 so much: it actually contains a small heater ...

Quote
The Si7021 contains an integrated resistive heating element that may be used to raise the temperature of the
sensor. This element can be used to test the sensor, to drive off condensation, or to implement dew-point
measurement when the Si7021 is used in conjunction with a separate temperature sensor such as another Si7021
(the heater will raise the temperature of the internal temperature sensor).

TomWS

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Re: Tiny TH Mote
« Reply #16 on: August 30, 2015, 01:51:46 PM »
To package the Tiny TH Mote I needed to make a worthy 'enclosure'.  While I don't have my full complement of woodworking tools at my current digs, I was able to cobble together a useful collection of tools to make something close to what I had in mind.

In the attached photo, you'll see a composite of the progression from start to 'almost' finished (finished comes in the next posting since this photo is too large to include anything else).

The first panel shows a couple of scraps of hardwood, one Cherry, one Walnut, and the tools I planned to use to transform these scraps.  The small drill is used to drill a pilot hole to keep the two forstner bits aligned, since I had to drill these holes from opposite sides of the workpiece.  These are not drilled all the way through, but far enough to create a reference counter bore for later. 

The next panel shows the workpieces cut out using the hole saw.  I would have liked to go smaller diameter, but the scrap wood was too thick and the aspect ratio would have been wrong.  In any case, pretty rough looking at this point.

Next two panels show the mounting of the workpiece in my 'lathe'.  I had to go to a hand drill rather than drill press since the thread on the 'chuck' required running the turning  counter clockwise.

The next panel shows the first pass roughing to general shape and then the final panel shows the finished pieces with the center bushing still intact.

More following...



TomWS

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Re: Tiny TH Mote
« Reply #17 on: August 30, 2015, 01:55:19 PM »
Here are a couple of close ups of the finished pieces.  The circuit board will be covered with some screening, but I like the looks of it this way  ;)

Enjoy.

Tom

WhiteHare

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Re: Tiny TH Mote
« Reply #18 on: August 30, 2015, 03:44:23 PM »
Very creative!  I  like how you even made a temporary lathe out of your hand drill.

The device electronics and PCB are so tiny that I had imagined you would be putting them into a shell that was only just a hair bigger than they were.  The approach you took instead looks very nice though, and it's a clever way to keep your antenna wire straight and vertical, like a plumb-bob. 

Would it make any sense to give the PCB a larger air gap (or possibly some insulation) all around to mitigate effects like thermal mass and/or self heating?  Or are those likely to be so small it wouldn't matter?

Also, am curious: if you ever needed to reprogram it, would you be using OTA wireless upload programming , or as during development do you have a jig with pogo-pins that fits into the depression for it to physically dock with?
« Last Edit: August 30, 2015, 04:01:01 PM by WhiteHare »

TomWS

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Re: Tiny TH Mote
« Reply #19 on: August 30, 2015, 04:12:26 PM »
The device electronics and PCB are so tiny that I had imagined you would be putting them into a shell that was only just a hair bigger.
Ultimately that's the plan, but, as I said, you can see in the photo showing the rough turning the tool I used to 'cut' the profile - a file with a flat and a partial round side.  When I get back to my workshop I'll be able to turn a decent piece out of a properly thicknessed piece of wood.
Quote
Would it make any sense to give it a larger air gap all around to mitigate effects like thermal mass and/or self heating?  Or are those likely to be so small that it doesn't matter to you? 
I don't anticipate a problem with this, certainly not self heating - this thing draws virtually no power!  The sensor is an SI7021 which you can see pretty well in the Cherry photo (U2) and it's positioned so that normal convection airflow will affect it.  I want to measure room temperature and that includes the walls.  I don't need instantaneous response.
Quote
Also, am curious: if you ever needed to reprogram it,
Why would I need to do that?  8)
Quote
would you be using OTA wireless upload programming , or as during development do you have a jig with pogo-pins that fits into the depression for it to physically dock with?
For the moment, it'll be pogo-jig reprogramming until I get Joe's bootloader...  The module is only friction fit into the back cavity so pulling it out to reprogram is trivial.  The package worked out pretty well in this regard.  The PCB is 26mm diameter, but leaving the holding tab 'residue' on the edge of the PCB allows it to friction fit into a 27mm hole.  So the wooden piece is drilled to 26mm in the front and 27mm in the back leaving a ring that acts as a stop when inserting the PCB from the rear.  Cutting the slot for the antenna wire was easy with a thin pull saw.

I should have mentioned that the pictures show a magnetic clip holding the end of the antenna wire - that clip is simply attracted to a drywall screw in the wall.  It turns out, with the thin cavity behind the battery (and the fact that the magnet sticks to the battery), I just need a small super magnet to attach the unit to the wall without needing the clip.    A 15mm diameter magnet will be perfect!

Tom
« Last Edit: August 30, 2015, 04:18:47 PM by TomWS »

luisr320

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Re: Tiny TH Mote
« Reply #20 on: August 30, 2015, 04:46:27 PM »
Recently I adapted my CNC to become a 3D printer. You could easily make any type of  enclosure in ABS or PLA. But nothing compares to a good handmade workmanship. Very nice.
« Last Edit: August 30, 2015, 05:44:48 PM by luisr320 »

TomWS

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Re: Tiny TH Mote
« Reply #21 on: August 30, 2015, 05:57:31 PM »
Recently I adapted my CNC to become a 3D printer. You could easily make any type of  enclosure in ABS or PLA. But nothing compares to a good handmade workmanship. Very nice.
LOL, did I mention that I have a CNC router at home?   ;)

Although, in this case, the wood lathe is much more appropriate.  The CNC router will be used to make the enclosure for the Thermostat variant of this Mote (it has an OLED display and, no, it won't run on CR2032  :)
Tom

TomWS

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Re: Tiny TH Mote
« Reply #22 on: September 11, 2015, 04:28:25 PM »
Stepping up to the before and after challenge set down by joelucid in his thread https://lowpowerlab.com/forum/index.php/topic,1269.0.html,
here is the the promised before/after photo of the Tiny TH Mote.  The two circuits are functionally and electrically equivalent, just packaged differently  :)

Enjoy.
Tom

luisr320

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Re: Tiny TH Mote
« Reply #23 on: September 11, 2015, 06:46:09 PM »

No seriously, do you intend to make them available trough Felix store? I would be interested in acquiring some. And they would be a nice addition to the Moteino family. Can you connect anything to them, like some external sensor, or only those onboard?

TomWS

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Re: Tiny TH Mote
« Reply #24 on: September 11, 2015, 08:24:16 PM »
No seriously, do you intend to make them available trough Felix store? I would be interested in acquiring some. And they would be a nice addition to the Moteino family. Can you connect anything to them, like some external sensor, or only those onboard?
I added the design files to the opening posting.  You can build as many as you want.  Not much room for expansion, however.

Tom

TomWS

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Re: Tiny TH Mote
« Reply #25 on: September 13, 2015, 11:00:47 AM »
I've added the ListenMode extensions to my RFM69_ATC library, including two new example files demonstrating how you could use the extensions in both Node and Gateway functions.

The new branch is at https://github.com/TomWS1/RFM69_ATC/tree/ListenModeExtensions

Enjoy,
Tom

WhiteHare

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Re: Tiny TH Mote
« Reply #26 on: September 13, 2015, 12:18:04 PM »
Thanks!

What's the difference between the ATC and ATC_WL examples?   I guess WL are the versions we should use, as they were the ones you just today uploaded.
« Last Edit: September 13, 2015, 12:36:41 PM by WhiteHare »

TomWS

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Re: Tiny TH Mote
« Reply #27 on: September 13, 2015, 01:07:44 PM »
Thanks!

What's the difference between the ATC and ATC_WL examples?   I guess WL are the versions we should use, as they were the ones you just today uploaded.
'WL' versions are 'with ListenMode'...  ;)

Tom

TomWS

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Re: Tiny TH Mote
« Reply #28 on: September 23, 2015, 09:08:22 AM »
I've added the ListenMode extensions to my RFM69_ATC library, including two new example files demonstrating how you could use the extensions in both Node and Gateway functions.

The new branch is at https://github.com/TomWS1/RFM69_ATC/tree/ListenModeExtensions

Enjoy,
Tom
The ListenModeExtensions branch now has the update to remove the inter-packet delay from sendBurst().

Tom