@Mishka The specs on the fx-260 solar calculator says it needs at least 50 lux for adequate power, but Dave Jones tested it on youtube and found that 20 lux was sufficient. Unfortunately, he didn't measured the shorted current, so it's hard to know how it compares to the cell on the solar calculator that you tested.
@xmonika I like the nRF52840 SDK. It includes an official j-link and can also be used to burn software to any attached nRF52840 by simply dropping the hex file onto the j-link virtual drive. Of all the options, I find it the easiest, but that's me. Other people use and seem to like the st-link or or black magic probe or dodgy copies of the j-link or clones of black magic probe. Different people seem to like/prefer different things. I read that Particle now has a programming tool as well for its Xenon device, which is basically their version of the nRF52840, and I think I may have read that it works with non-Particle nRF52840's as well.
There's also BLIP, which is new and sounds kinda interesting: https://www.crowdsupply.com/electronut-labs/blip
@Nca78 Thanks! You said it better than Dave Jones did. 
You've convinced me. 
@Omemanti said in What did you build today (Pictures) ?:
I also want to connect a touch sensor to it
You may not need an extra sensor. I haven't yet tried it myself, but supposedly the nRF52 has capacitive touch sensing built in.
@NeverDie I think you are missing the point about the battery. Dave Jones was right as the energy produced by the watch over several years was similar to the one from a coin cell. And before those years pass we all know what happens to electronic devices: they get replaced. So the problem of battery change they pretended to fix was not a real "problem" as the product life is shorter than the battery life. It had very limited functionality and only manual synchronization with the smartphone, and a very basic app.
It's probably a similar thing with the new version, solar panel increases the available power but it's still in the uA range and functionalities are very limited, the "full color" lcd has no backlight, GPS use must be limited to a few mins per day, same for heart rate monitoring etc. So in the end a watch with similar functions and a li-ion battery would be smaller, half the price and only need a charge every 6 months. 2h of charge twice a year is far from a constraint... In addition the battery powered watch would allow you to run constant heart rate monitoring, have long GPS sessions like 2 hours of running etc etc if you accept to charge more often.
It's not as bad as before but it still feels like they made the watch because they needed a product to use the technology, and cut down the functionalities until power consumption was low enough to fit the technology. While it should be the opposite, technology should have been improved until it was able to power a smartwatch with "normal" functionalities.
I'm pretty sure many users of the new version will end up removing the watch from their wrist to expose it to the sun, and that it will last way longer than the charging time of a typical smartwatch
@mfalkvidd I'm impressed that they've pre-sold over ten thousand of them.
Changing a watch battery isn't particularly easy, especially on a waterproof watch, because AFAIK doing so generally ruins the waterproofing seals. Dave Jones may have underestimated the hassle factor.
Also, there's a watch that was made by the authors of "The art of electronics" that the authors say consumes just 1 microamp, and that was more than a decade ago.
So, bluetooth aside, a TEG should generate more than enough to run a watch like that. I don't doubt that at least some amount of bluetooth or ANT or some other kind of radio communications could be supported. Maybe not a lot, but at least something.
It's easy to forget that the original consumer LED watches would light up only when you pressed a button, and yet they sold anyway. If you did it that way, then it should be easy, and it would leave more of a budget for the radio communications.
@mfalkvidd Dave Jones reviewed that very watch and was fairly negative about it:
EEVblog #945 - Thermal Powered Smartwatches Are GIMMICKS! – 29:53
— EEVblog
Even so, it looks as though they raised over two million dollars!
This guy had an interesting idea that could probably be improved upon:
To make the watch thinner he spread the parts over different links in the wristband.
https://www.thingiverse.com/thing:718989
@Mishka Looks as though an array of BPW34 can actually be packaged together fairly tightly.
It still wastes some real estate, but not as badly as what I had imagined.
I suspect they wouldn't do well under indoor LED lighting though, as they seem to have peak sensitivity at around 900nm, which is infrared.
Maybe the reason solar cells like the SC-1338-4 are so elusive to find in the usual parts market is that the manufacturer is basically just buying a relatively cheap 5x5 or 6x6 inch slice of monocrystal that probably looks like:
and then carefully breaking it into bits of such a size that when wired together they exactly fit whatever net size the buyer wants. Though I've never tried it, I presume that you or I could be doing very small scale "manufacturing" ourselves if we were so inclined. Obviously some people make their own DIY 100w panels this way, but from what I've seen those people do so by soldering foil tapes across the front face of the monocrystalline slices, which presumably these cells would be too small to do. Hmmmm...., this now has me curious as to exactly how the bits get wired together. Anyway, provided they're not too hard to make, the upside to DIY'ding small solar cell planels would be getting any size/voltage combination we want plus freedom from having to scavenge pre-made cells from pricier consumer products.
