I want to sell my projects as a private individual, as a hobby. I don't want to start a company. Is that legal in the EU? anyone know?
This particular point is not covered by any EU regulation AFAIK. It's your local regulations you have to look at.
In general, selling stuff as an individual without a company is tolerated in most european countries AFAIK as long as the amount you make per year is not a "significant" part of your total income. I suggest learning more about danish law though on this particular topic.
Do I need CE-marking on my hobby projects to sell them?
This one is a bit tricky. For a very basic introduction:
https://cemarking.net/do-your-products-need-ce-marking/When selling electronic devices, it seems pretty hard to avoid at least complying with the EMC Directive, and probably RoHS as a minimum set. If the device connects to mains, the Low Voltage Directive will be required as well, but you may circumvent it if your device is strictly powered with a very low DC voltage and the burden of the LVD is put on the shoulder's of a third-party mains adapter (which is itself compliant.) If your device contains some radio link, you may also need to comply with the RED directive.
In any case, you can read the directives, they are all free to download. For instance, the EMC one:
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014L0030Take a look at the "Scope" and "Definitions" sections.
To keep the EMC directive example, one major point to consider is the following:
* Scope: "1. This Directive shall apply to
equipment as defined in Article 3."
* Definitions: "(1) ‘
equipment’ means any
apparatus or
fixed installation;"
"(2) ‘
apparatus’ means any finished appliance or combination
thereof made available on the market as a single functional
unit, intended for the end-user and liable to generate elec
tromagnetic disturbance, or the performance of which is
liable to be affected by such disturbance; "
"(3) ‘
fixed installation’ means a particular combination of
several types of apparatus and, where applicable, other
devices, which are assembled, installed and intended to
be used permanently at a predefined location;"
From these definitions, whether your products are within scope all depends on what they are exactly. For instance, a development board would usually NOT qualify as an "equipment". For a fully assembled device, that is a lot more tricky. The main issue I see there is that I haven't seen a clear definition of the term "end-user" that is used throughout the directives... I guess you can assume it means the last customer that will use the product in the supply chain.
Do any of you have any experience in selling, hobby projects in the EU, as an individual?
As an individual without a company, nope. But I have sold second-hand stuff before as an individual, probably as most of us have. I would expect it to be basically the same - as long as it doesn't qualify as your main "job" or source of income...
If it matters I live in Denmark.
As I said, regarding selling stuff without a company, it certainly matters. But regarding the CE mark, it doesn't. The CE mark is required (when it applies) for selling products in the EU. The country of origin doesn't matter. *Making* products inside or outside of the EU has no impact on the CE mark requirements. It's just about where you are going to sell them.