And in less than a week please meet the revision 1.1.

This release addresses annoying NFC bug introduced in rev. 1.0. Such, to cleanup schematic I've moved NFC capacitors to a dedicated space where the C18 was turned upside down in order to improve text readability. This led to C18 net changes which were overlooked for the PCB. After zone refill it resulted in tying the GPIO_P0.10/NFC2 to the ground thus making the whole NFC antenna defunct.

From the good, this revision adds highly requested mounting hole to the main board:

Have a nice time!

@neverdie said in Raybeacon: nRF52 on-the-go Development Kit:

The F-type trace antenna on the esp8266 esp-12F seemed to be the best all-around solution, so I was previously guessing the same would probably be true for the nRF52 as well.

Well, antenna parameters are relevant only to resonant frequency. As long as it matches 2400-2485MHz it should work just fine.

This one on the photo looks like SWRA117 by TI. I used those from KiCad standard library as a simple drop-in solution and they are quite nice.

Then again, the Fanstel BT840X trace antenna seems to be by far the best so far, and it's bigger than the esp-12F antenna:

Yeah, where reduced size is a must, meandered antennas (like the SWRA117 above) are good compromise to straight inverted F-type antennas. Otherwise a straight IFA might show slightly better efficiency.

I'm guessing maybe part of the reason it does so well is because it has less insertion loss than an externally mounted antenna. So, to your earlier point, putting a BT840X inside a cantenna should easily beat externally mounting it to one.

Placing antenna into a can makes to it about the same thing as acoustic guitar body to sound wave - it helps create standing wave and direct it into one particular direction. This simple trick promises to give +10..+15dBi - about the same gain as a power amplifier.

The difference, of course, in radiation pattern. This actually defines the need: do we need long range connectivity in one direction, or it has to be rather omnidirectional? For the first case - use directional antenna, then shape the beam with a can (cheap) or parabolic reflector (affordable), if still low - amplify. Of course, size matters so a small and simple properly placed reflector would make it too. For the latter case just stick to omnidirectional antenna and amplify.

That said, my best experience to date has been with dipole antennas. They're larger still, but they're also very easy to make. Some people have even hacked them onto nRF24L01's and report much better range. I'm guessing that's at least partly because it compensates for the too small ground plane on those devices:

Bigger ground plane usually promises better performance indeed and the module looks very small.

But to be honest, I don't know will the dipole improve anything or not. The nRF24 has balanced antenna feed line so at least it should be possible to connect dipole directly to the module (which is not the case with nRF5). But in order to do this all extra networks must be cut out, and even in this case it's very unlikely the antenna and RF output will match each other. Assuming that both the DIY dipole and the Cypress MIFA are omnidirectional antennas I don't think that the detuned and very likely out of band dipole would beat the original design, sorry.

Luckily, at 2.4ghz the antennas wire length isn't as awkward as it is at sub-ghz. Maybe it could be shrunk down using two squiggle traces instead of just one?

The RF output has 0dBm. Next, the default omnidirectional antenna tries to radiate it with 0dBi gain. Now it's possible either amplify, or shape the beam, or do both. A directional antenna (including reflector as part of it) could help gain up to +20dBi in front (which roughly means you'll have -10dBi in other directions). Amplifier could add +15dBm more in all directions. So it depends.

IMHO the options (inclusive) are as follows:

• Use reflector. Pros: high gain, cheap. Cons: size. Note: results in directed antenna (which may be both good and bad).
• Replace antenna. Pros: better radiation pattern. Cons: needs tuning.
• Install amplifier. Pros: immediate tx/rx gain boost. Cons: extra cost, needs tuning, may drain battery on low-powered solutions.

Hi,

I'm pleased to announce that the first major release of the Raybeacon DK is out. The revision 1.0 offers all the mentioned features and can now be ordered from your favorite PCB service. For highlights please take a look to the OpenHardware description, for details (and sources) please visit the Raybeacon project page.

I've published project BoM on the Octopart where you may easily estimate components. Please note, the aQFN73 package may push you to higher PCB production line. In particular, it suggests ENIG finish and also requires 5 mil track width / clearance, so expect increase in production costs. At the same time I've tried to keep design of the extension slices at the most affordable price so it should be easy to get 10 for $5 and have some DIY fun during Xmas holidays.

The project still work in progress. Such, the radio was tuned for the nRF52840. The nRF52833 may work just fine or may be out of tune. I'm going to order several boards with 833 for that purpose, but it may take a while so please use 833 at your own risk.

And, of course, please don't hesitate to share your feedback, it will be highly appreciated!

Hi @Nca78, I've placed the order on the PCBWay in early January, so it's almost finished. The factory just recently restored assembly services for some kind of boards including this one. Hope to have it in hands within a week or two.

@monte 1) To control all the sensors and 2) to be monitored by the network.

@scalz said in Everything nRF52840:

@NeverDie I think you need to hold it, but it looks there is "coded" holes/slots for helping and correct positioning.

You may want to use TC clip for long-time debugging or odd boards like this:

Thanks!

The board uses aQFN73 package which is kinda two-row BGP with 0.25 balls, so soldering it at home may be quite tricky indeed. I've ordered assembly

The aQFN73 is common package for both nRF52833 and nRF52840. In this particular board you may safely use either nRF52833 or nRF52840 of your choice (need 105ºC and direction finding, or rather more memory and the CryptoCell unit?) The only other thing you have to do is ensure pi network uses correct components for the selected SoC (I'll update the BoM as we can tune it) - the PCB remains the same. Generally speaking, many features are just matter of your BoM. Just do custom assembly by dropping support for USB (C20), NFC (J1, C18, C21), IR LED (or replace it with usual LED), buttons, nRF DCDC, 32KHz crystal, and so on.

On the other hand, if you need an extra stuff for your device (like a MEMS, or microphone, or air quality sensors), you may develop and attach an extension "slice" board. The "slice" supposed to be placed on the back side, i.e. right behind the CR2032 battery. Thus way it will create a kind of sandwich (or probably better said, burger): the Raybeacon board - battery - custom slice board. The red board on the screenshot is an example of such slice developed for my friend. It provides ultralow-power accelerometer, magnetometer, and gyroscope - all in all, we have just CR2032 for that.

@alowhum said in Everything nRF52840:

To what extent Bluetooth has useful smart home profiles
To what extent Arduino devices could present themselves as smart home devices using those profiles.

Well, the BLE has a lot in common with REST. You have to have one or more central devices (clients) which will query peripherals with sensors and actuators (servers). Communication is P2P, but broadcasting is also supported to some extent (various beacons are well known examples).

If thinking about it like a RESTful sevice, there is a number of API which were standardized. They call it profile, like in, for example, the Heart Rate Profile. The standard just assures that any heart rate monitoring device will talk the same protocol as any other one - that's it. I don't think there is many standard profiles for smart home devices (if any). At the same time, there is the Project Connected Home IP.

Of course, there is nothing which may prevent somebody to implement his own interface. If it will be successful enough, it will be later possible to contact the SIG group and promote it to a standard.

Please also note, that for serious boradcasting there is the Mesh. In a nutshell it works similarly to Ethernet switches. Interesting side effect is that it's possible to build a Mesh network physically wide thus delivering packets over long distances. Of course, if you want to go global, the IPv6 will be the right choice to go. It will require a standalone BLE enable router though - it will connect the devices to the Internet.

To what extent older Bluetooth chips can work with newer device profiles (it would seem a software upgrade should be enough?)

As long as they support Bluetooth Low Energy - i.e. version 4.2 or above.

By the way, for hand-soldering version I planning to employ nRF52833 in 5x5 QFN40 package when it will be available. It won't be possible to install anything but 833 there, but the PCB itself should be way more affordable to manufacture and assemble. I think the new board will be 100% compatible with existing "slices" . The current form factor depends on battery size in the first place, and I think it will remain the same. Unsure those 5mm will make big difference if we switch from 2032 to 1632 and loose about 50% of capacity.

@Nca78 said in Everything nRF52840:

A very interesting project, too bad they are using NRF52832 and not NRF52840, the max SPI speed on ...32 is too low (8MHz) and I'm afraid the LCD refresh will be annoyingly slow

It might be also interesting to employ the Sharp LS012B7DD06 which is a round 240x240 6-bit color memory display consuming 11 µW in static mode. It will be far away of the PineTime's $25, but with the CryptoCell, NFC and other stuff it might worth it.

Shall we create a repo?

@NeverDie My thought was that amorphous silicon (a-Si) cells have better spectral response to artificial light than crystalline cells (c-Si). However, after investigating this a little bit I've found that this doesn't seem to be true. Instead, it's shown everywhere that c-Si cells have better response to every wavelength:

Moreover, when the light source has wide spectrum (like the sun or an incandescent bulb), c-Si panels take the advantage and produce significantly more energy from the same source, and this all explains why a-Si cells are almost two times less effective than c-Si (roughly 8% vs 20%). Please note, because of narrow spectrum a LED lamp will be obviously inefficient for a PV panel.

But at the same time, there are reports of a-Si cells being 4x more effective in low light than crystalline. Indeed, both crystalline and poly-crystalline cells may degrade a lot:

The seem happens due to low parallel resistance of c-Si type cells. Shunt resistance of amorphous cells is naturally higher which results to less degradation of Vmpp and hence higher efficiency in low light conditions. Some paper show the shunt resistance rather low, when other mentions it relatively high, but at extremely low power conditions even 20 kOhm may be too much.

In short, a-Si cells are tend to produce fairly better results in very low light environments. But they can't leverage from wide spectrum sources, yet are subject to the Staebler-Wronski effect when exposed to direct sun (which can be reversed to some extent by heating the panel). In case if the light source is bright enough (around 1000 lx and above) a c-Si pannel should be preferred.

Finally, there are some other kind of solar cells, in particular those made from III-V semiconductors compound and promising even better low light performance.

@scalz Yeah, next time I just have not read, but watch the video.

My impression was that the snow coating acted like a mirror thus greatly extending the range. But I admit 14 km is ridiculous. So sounds like a challenge

@scalz You're right. They did NB-IoT, not BLE. Shame on me!

@scalz No. The nRF9160 DK has nRF52840 on board.

@NeverDie The pads are usually made of silver. If thin enough it may look like the crystal. But the crystal itself may also be light enough - they produced with painting added for better light absorption.

In a meanwhile, here is the nRF52840 range test with Johanson 2450AT18D0100 chip-antenna and SAFFB2G45MA0F0A 1dB attenuator
the nRF9160 range test: https://www.youtube.com/watch?v=p1_0OAlTcuY (spoiler - 14 km).

@NeverDie No no, by polishing I mean only the edge after cutting. I'd prefer to have it nice and clean just to avoid possible impact of cell layers which might cause shortenings. It's also very interesting to know that the cell has 3D surface - cool.

How easy it was to solder anything to the cell? Have you tried to solder anything to crystal raw surface? My concerns is that after the cell will be cut it will lose interconnection of conductors so it would be nice to restore the metallization layer.

@NeverDie Wow, nice collection! How do you think, may it be reasonable to glue cut cells to a quartz or glass base? Would it compromise effectiveness?

IMHO the right way to cut them is either laser or high speed CNC. Also, CNC cut crystals may require extra polishing.

Just asked a couple of local vendors for a single cell, waiting for their reply. BTW those cells are usually of 18-19% energy efficiency, so the only way to beat Amorton or IXYS is to cover larger areas.

@NeverDie My nearest laser service costs about 3-4 dollars for one running meter, can cut 2 mm steel, so never thought about that. On the other hand, with enough number of passes it virtually should be possible even on a DIY CD-ROM laser engraver, especially if mounted on a CNC which is usually more precise than lasers.

I'm expecting that at least three crystals will be required to gain 1.5-2V. For a circle, it sounds reasonable to cut three or four sectors of equal shape. Maybe a 3D printed pallet can be used with top layer protected by epoxy. But I think for the best result additional metallization will be required anyway.

@NeverDie Interesting. I think the cell may be carefully cut with laser and then properly remetallized. Perhaps can be done with a typical tin based solder paste with some proper flux (I don't know, originally some kind of silver paste is used). Fixing the cell itself into epoxy should be easy.

The nice thing about the process is that it should be virtually possible to create cells of arbitrary shape. However, in order to get usable voltage it might require to build a panel.