The key qualifier for Show HN is that it's something you've made that other people can play with. It needs to be somewhat complete and working – enough for basic demo/testing – to be eligible. If it's a plan or ongoing effort to get something working, it's not ready for Show HN. If there's an interesting story behind the ongoing effrot, it can be a blog post, but not a Show HN. With hardware projects, a video is sufficient, but the video needs to depict the thing working.
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