Remember those RS232 to Eaton Leonard adapters I made a few months back? Well, there’s a need for me to develop a version which can run from 24VDC, so I did. The switching power supply mentioned a few days back is used in this (you can see its footprint there on the left), with the rest being the same as the other board.

I had to remove the reverse voltage protection (it just won’t really work with the high potential input voltage this needs), I’m using a resistor network instead of discreet resistors to make assembly easier, selected different LEDs (ones that use slightly higher current to go with the 120R network), and laid out the whole board again.

That picture up above is missing the documentation and logo layers, just to obfuscate things a bit. I may also tweak a little bit of the design, but I think I’m happy with it. It’s now 3″ x 3″ instead of the original 3″ x 2″, but that extra three square inches is needed for the power supply. Yes, there’s a bit of blank space still, but I don’t think it’s enough to make shrinking the board worthwhile. The cost difference between the previous PCBs and these is pretty much nonexistant, if I’m remembering the quote right.

I think I’m going to keep compacting the board. Hmm…

UPDATE: I just shaved a square inch off the board by bringing the top in 1/4″. LEDs were compacted a bit, logo made smaller, L2 moved, and more.

Well, the prototype power 5V switching power supply that I cobbled together seems to be working. Up there you can see it powering the first nuxx Audio Input Switch, just to give it some sort of load to work on.

Here is a photo of the bottom of it. It’s clearly hacked together, just sort of built up on the board so I could have solder connections and reasonably short wires. When I tried to breadboard it things didn’t work quite right, which I blame on switching power supplies being touchy about long rows of bare wire.

It’s pretty much a reference implementation (some variances in parts) and it produces what appears to be nice, clean power. I can’t see any noise on my scope. Granted, my scope is pretty crappy, but it does seem to show some noise when it exists. (I can’t afford a new scope yet…)

I’m happy with how it is working thus far. I need to put a bit more load on it, but that’ll be done over one of the next random couple of days. For now I can say that it had no problem giving me an even 5.000 VDC while powering the nAIS above and being fed 6.073 VDC. If I cranked the input up to 35.93 VDC (the highest I can get my benchtop power supply) the power supply was pushing out 5.074 VDC. Pretty good, I think.

Danielle’s TV-B-Gone
(Click for full res photo…)

Tonight I helped Danielle put together her first electronics kit, one of Limor Fried’s open-source TV-B-Gone kits. She’s soldered a bunch of stuff before from when she briefly went to Kettering, but this is the first functional kit. And, of course, it works!

Well, it at least turns off my TV almost instantly… I imagine that it’ll work pretty well on whatever other ones. At $20 it’s a good, and useful first kit… Imagine actually being able to turn off all those annoying TVs in places like the doctor’s office waiting room, school hallways, and (hopefully) the advertising things on gas pumps.