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

1901 points l2silver | 1 comments | 27 Apr 23 15:04 UTC | HN request time: 0.31s | source

Maybe you've created your own AR program for wearables that shows the definition of a word when you highlight it IRL, or you've built a personal calendar app for your family to display on a monitor in the kitchen. Whatever it is, I'd love to hear it.
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jwr ◴[28 Apr 23 14:03 UTC] No.35741387[source]▶
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…

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moron4hire ◴[29 Apr 23 01:51 UTC] No.35749246[source]▶
Li-Po isn't difficult to ship. You just slap a certain sticker on the outside of the box and pay a little extra. Otherwise, it's no more effort.
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1. crote ◴[29 Apr 23 03:58 UTC] No.35749894[source]▶
LiPo is an absolute nightmare to ship in nontrivial quantities. The trickiest part is all the paperwork. Shippers really do not like it, because it places a lot of extra restrictions on the way they are allowed to ship it. This is made 10x worse when you are trying to ship bare batteries.

This is also why companies like Sparkfun don't sell batteries internationally. Adafruit used to have this restriction too, but they seem to have recently changed that.