You can see a few more pictures on the "Shop" page . They are hidden behind the "View product"-button. I've extracted a few links and modified them to link to larger images [1-3]. The power supply is connected via a barrel connector as can be seen in image . I guess I would have used a USB power supply instead, just because of their ubiquity.
You're also potentially limited by the USB spec on current draw. There are ways around this, like ICs that will detect if you're connected to a charger or a data port. The barrel connector is also quite ubiquitous and I designed the power entry to work across a wide range of DC power adapter voltages.
I have also discovered the previous version now (, if someone else is curious as well) and will have a look at it later.
1) what's the timezone?
2) what about DST?
The first is quite complex and requires knowing more than just lat/lon. Dates of DST also do change over time according to policy. The only solution I saw for these would to go full IoT so it could talk to NTP servers or have a control interface, and that would ruin the plug-it-in-and-it-just-works minimalism I was going for.
My understanding is that in the US, this device would be classified as an "unintentional radiator". If you want to sell it as a finished product to consumers, then you're legally required to get it tested by an ANSI C63.4 compliant lab to ensure that it meets the legal limits for RF emissions into the air and the power grid. AFAIK the typical cost for a round of testing is >US$1000, and it needs to be repeated if you make hardware changes of pretty much any kind.
I've occasionally considered making and selling projects kind of like this one as a hobbyist, but it seems like the cost of compliance testing means that you have to be reasonably sure that you'll sell at least a few units, or else you're just throwing money away.
I've studied SMPS design and am not totally oblivious to conducted and radiated EMI issues. I took several considerations in the project like analyzing current loops and taking near-field measurements on a spectrum analyzer. However, what ultimately matters is what happens in the testing chamber.
What is the blue dot for?