Ask HN: Most interesting tech you built for just yourself?

Oh, I think I have a good one. I had an HP-25 calculator as old as myself, and couldn't use it. The original battery pack contained two sealed NiCd cells, which obviously failed many years ago. Most people replaced their NiCd cells with new ones, then with NiMh cells, or even alkaline AA batteries. This was always problematic: newer batteries were slightly larger and never fit well. Also, the power consumption of a calculator with an LED display was significant, so frequent battery replacements were needed. And the original HP charger was risky and could easily destroy the calculator.

So I designed and built a wirelessly (Qi) charged battery pack for it.

https://partsbox.com/blog/wireless-charging-for-a-hp-25-calc...

After a year of use, it's totally over-engineered and has so much energy and so little idle power consumption, that I have to remind myself to charge sometimes, the thing lasts for months.

I'm the only user. There are many people who wanted to buy one, but the step from a hobby design to small-scale production is a big one and it simply doesn't make business sense. Especially with Li-Po batteries being difficult to ship and potentially a hazard. I guess maybe if I found a manufacturer that would be willing to take the design and manufacture it on demand, taking over all of the shipping/support issues…

I made a personal website [1] that aggregates my notifications from GitHub and Gerrit in one stream. It updates in real-time without me needing to refresh the page.

It also hosts a small set of personal Go packages. For this, it implements a git server, module proxy protocol, issue tracker and change tracker. At some point, I want to differentiate the code review UI with nice-to-haves specific to Go, but haven’t gotten there yet.

I’m playing around with compiling the whole thing (written in Go, of course) to WebAssembly that runs client-side, along with server-side rendering for the initial page load. This is mostly to make iteration easier and faster for me.

It also lets people leave comments or reactions to blog posts and such by signing in via a URL rather than username+password.

[1] https://dmitri.shuralyov.com

I'm a credit card point junkie so I always volunteer to pay the bill at dinner or drinks. But, if everyone doesn't get roughly the same thing, it becomes a massive headache. I got fed up with having to manually tally up what everyone ordered and then hunting them down individually to get paid back.

Surprisingly, I haven't found a good tool that addresses this, so I spun up my own. I didn't want to force my friends to download another app just so I can get paid back so I tried to make it mostly SMS based.

You text a picture of the receipt to my Twilio phone number. It triggers a serverless function that runs AWS Textract to itemize the receipt, then stores it in a database. Twilio responds with the unique URL for the receipt and I can text that out to my friends so they can claim their own damn items.

Win win, I get the points AND I finally get paid back.

Ha! The Final Sacrifice is on tonight. That's one of the very best MST3K episodes.

I would love to do something like this for my kids. They're constantly begging to watch Youtube, which I limit pretty heavily. Something like this could allow me to stick some pre-approved videos into a queue, and maybe even make an allowance for a half-hour of some of the ... dumber stuff that they like at a certain time of the day. I could also slip in some Kurzgesagt, Mark Rober, content that they may not otherwise be that interested in to surreptitiously educate them ;)

I like thinking out loud, but don't like having to listen to voice memos. So I created a syncthing folder that is synced between my phones and my home server, and created an iphone shortcut that records voice memos and saves them into that folder (and then opens the iphone syncthing app so that it'll do the sync). I have a cronjob on the server that looks for new audio files in that syncthing folder and transcribes them with whisper, formats them into a nice looking pdf, and sends them to the printer. So now I can be anywhere, record a voice memo, and come home to find it sitting in my printer.