Just a quick and dirty case for the LM2596. In my case it's to step 12V down to 5V to power my ancient home CCTV unit.

So, a few days before Christmas, and full of the joys of the season, I went out to my car, only to discover that some @#&$bag had stolen the chrome dust caps from my car wheels! Thankfully I don't fit expensive ones anymore because it's not the first time it's happpened.

But it WAS the first time it's happened when my car was outside my garage, in full view of my CCTV. So, when I got back later on, I whipped out the CCTV's SD card to catch the varmints in the act. But Sod's Law prevailed: It turned out that the CCTV hadn't recorded anything. ...Since August!! Arrrgh!

Something in the CCTV's wall wart had died and left it putting out a very coarse 5.2V, 50Hz, wave. So although the lights were all on, it was just acting as a flickering candle LED, and none of the processing side was powered for long enough for it to boot into record mode.

I opened the wall wart to see if anything was obvious, but there was nothing I could see; no signs of magic smoke, or PCB skidmarks, not even a smell of overheating plastic to give me a clue.

I then rummaged around in my shoebox of wall warts, but I couldn't find anything that would give me 5V at the necessary current (2A). I probably could have re-purposed a USB charger, but there were two problems with that: 1) I didn't have a USB charger, and 2) I didn't have a USB charger. I know I said that twice, but I felt that it was such an important obstacle that mentioning it only once really didn't do justice to how big of an obstacle it was.

But all was not lost. You see, whilst the CCTV box uses 5V, the cameras don't. They all run from a 12v supply which is basically just a glorified laptop brick, with barrel jacks. One of the barrel jacks was unused, and I had an LM2596 converter and a spare barrel socket in my spares cache, just waiting to step into the breach. A few mouse clicks later I had a housing ready to print. and once again the smell of molten plastic pervaded my living room.

Once printed, it didn't take long to solder the barrel socket and the lead from the old wall wart onto the board - although I won't claim it's my neatest ever soldering job; my eyesight is getting terrible for close work!

It all works OK, but I'll be honest it's not an ideal solution; DC-DC converters are inherently noisy, so you can see the effects of voltage ripple on the CCTV's monitor screen. But I can live with that for now because at least it's runnning again. And the image is still plenty good enough to catch dust cap thieves should the pieces of @#&$ ever return for another go.

So I've just sharpened my bolt cutters in readiness, and I hope it's still legal to castrate thieves if you catch them in the act!

Happy Christmas, and a wonderful new year to all.

Category: Electronics