Improving/repurposing existing tools and making new ones - my take on this
Some time ago, I found an article about modding soldering stations for safety (in Russian) (Google Translate). The problem is hot air guns suddenly melting and setting themselves on fire, supposedly, because TRIACs that control them fail.
Here's a video of this phenomenon:
Here's one more:
First, an explanation on how most Chinese hot air guns work.
I sometimes go on an eBay bidding spree, trying to get items of <1-2$ price which I don't really need right now but might need later. The same was with a nice LED dimmer (which I'd never plan to buy!) I found and subsequently won:
Sometimes I need to set up a little network infrastructure to connect a multitude of devices to a network. I also can't be picky about PSUs, as I can get either a barrel jack one or a simple USB socket from my computer. Also, I need something to power all those Raspberry Pi boards I sometimes need to experiment on, and given all the environmental constraints (that is, in some places where I work there aren't enough wall sockets) one USB port with enough power makes all the difference. With that in mind, I've took a 8-port network switch I've been using for ages and repurposed it a little.
Network switch in question needs 5V. In its first revision, I used a LM7805. However, this proved to be unviable because the thing would heat up a lot from 12V, even with a heatsink.
So, I turned to one of those fake-LM2596 DC-DC modules eBay is offering, and they're pretty decent compared to linear regulators in terms of efficiency. That worked, and worked pretty well, but these regulators are capable of more and I wasn't tapping into that capability. So I added a USB port which could provide 5V at enough amps to charge/power things. The switch both has a USB cord tapped into the 5V line and a 5.5/2.5 barrel jack connection which is connected to the DC-DC Vin.