Some time has passed since my last post, and for that I am sorry.   I like to write about my technical endeavors, however, I’ve been feeling “out of time” lately.   Its not that I work late or anything like that, time just seems to disappear.   I get home from work around 6, catch up on personal emails and some news, then its time for dinner, and before I know it, it’s 11 pm!  Where did those 5 hours go!?

I have a list of things to write about, and I’ll be taking a little time off from the daily grind over the  Independence Day holiday to catch up on stuff.  Hopefully I can get some of these things written down, and make room in the ‘ol brain for keeping better track of time.

On a maintenance note, I’ve finally gotten around to upgrading my wordpress to 2.0.2.   The constant stream of spam which I hope to keep hidden from my readers has prompted this move.  I have some new spam-fighting plug-ins working behind the scenes, hopefully they won’t interfere with valid comments.

RS232 Utilitarian Project

If necessity is the mother of invention, being cheap must be like a step-father or uncle or something?

I needed some level shifters / line drivers that I could easily use on the breadboard for microcontroller projects. Rather than give some other entrepreneur $10 for their version, I made my own.

MAX232 rs232 line driver level shifter

Nothing particularly special here, aside from the cool factor added by the two LEDs which light on RX/TX events. The chip is a standard MAX232 clone, and I’ve got five 1uF ceramic caps mounted on the back side. The leds are driven by some SOT-23 transistors. To make things simple, I stuck the pin header through the board the “wrong way” and forced the pins almost all the way through their plastic spacer / retainer. This way the unit plugs right into the breadboard, and lays there real nice, even with a heavy serial cable attached.

MAX232 rs232 line driver level shifter

So far so good, it works well with my bootloader at 115kbps, so I figure that’s good enough!

EDIT: Eagle SCH and BRD files available here (7-zip format).

Almost a month and nothing new?

Jeeze, almost an entire month gone by, and nothing new from me?

Well, almost … I did finally fill in the [Image Missing] place holders in my pcb fab article.

I’ve been doing a little tinkering, but also working outside … spring time has arrived for my little microcosm and the outdoors needs tending to. I’ve also been having a bit of a mole problem, so lots of time has been wasted trying to deal with them.

I have been in the lab a little, working on a few projects, and burning out parts … I burned my last ‘free’ tps61040 boost regulator, so rather than ask TI for more freebies, I’ll buy some this time, luckily they’re not too expensive. Also I managed to bust a red Luxeon III Star. I had two of them wired in series and hooked ’em to a 12v supply, without any manner of current limiting … needless to say, it was bright for an instant and then dark. Luckily only one star was killed, the other lives on. Here’s a few post mortem pictures, I removed the little lens, which really was filled with silicone goo just like Lumileds claims!

remainder of a red luxeon star, sans lens

You can see a little bit of the goo remaining on the heatsink structure, as well as the fine gold bond wires and fine grid used to power the die.

remainder of a red luxeon star, sans lens

Here’s a bit of a closer view.

This die still works… when I poke at it with the leads of a 3v battery pack, it lights up blindingly bright… wonder how long it will survive before oxygen or something else kills it?