Friday, October 26, 2007

what is it?

I do a lot of scrounging.
Admittedly I just like taking things apart, so the motivation is not always to get useful parts.
But once you have a large junk box full of old circuit boards you just know that one of them is carrying the part you need.

Conversely, I often find myself staring at a board and wondering "what the hell is that thing?"
I have a pretty good basic knowledge of electronics, and I think I can identify the general class of a part without much help, but there are always mystery items which need some research.
I like research.
What better way to waste time then by learning something?

Along the way I have collected a few links which I use to try and figure these little mysteries out.

Here are a few:

The impressive sounding FCIM Component Identification Tool it is at least 12 years out of date, but then a lot of the things I am scrounging from are old too. The site is hard core Web 1.0, and a little hard to navigate, but they show LOTS of useful info on package types, general usage guidelines, and part numbers.

For a newer resource that includes lots of surface mount (SMD) codes try TKB-4u (The Technical Knowledge Base for You!) which lists lots of codes, and some basic info on identifying those tiny parts.

There are more lists of SMD parts at TALKING ELECTRONICS as well as useful information on op-amps, voltage regulators, opto couplers, and some basic older ICs.

For semiconductors, once you have found the part number you will also need to know how to use it, and for that you need a data sheet. Data sheets are like gold. They have the pin out, all the power specs, timing data, and often a reference circuit you can use as a starting point for your own designs. Finding a data sheet for an older part can be difficult, and many of the site which claim to have them want to charge you for them. Some time ago I discovered All Data sheets and have rarely had to look anywhere else.

Friday, September 28, 2007

blue LED POV and the Diecimila hack

the dyslexic pov device

I really wanted to make something cool with my new toys before the last make:philly meeting. I knew there was not much time, so I settled on a POV device. I figured that would be easy to show off, and would be a good way to interest people in the hacktory arduino/freeduino class. As it turned out, the hardware was the easy part. Here you see my attempts to get it to spell MAKE. Obviously I still had some work to do...

tiny blue leds

I found these great little smd leds on a junked keyboard pulled from the trash. Soldering them down with their individual current limiting resistors was a challenge. Unsoldering them from the keyboard was a nightmare! In the end I only ruined one. I really want to build a hot air rework unit.

Diecimila hack

Along the way I came across this post. Pure freakin' genius! I used an smd cap instead (because I had it and I am addicted to soldering tiny things), but other then that I can't add anything useful other then to say it works like a charm.

Sunday, September 02, 2007

Doing it the hard way

the Bare Bones "Arduino" from modern devices

I ordered 4 bare bones arduino kits from Modern Devices. But in a moment of false economy decided not to order a USB < -- > TTL cable for them. Instead I decided that I would use some of the parts from the SMD grab bag I got ages ago and make one myself. My old laptop has a serial port, so I did not have to contend with USB, and it is "old tech" so there is lots of info out there.

rs232 < -- > TTL cable schematic
Finding a suitable schematic was as easy as looking at the serial Arduino schematic and finding the rs232 input area. I rounded up all the parts, and used a peice of prototyping board designed for SMD parts from OnePas ( I also dug up a DB9 connector in a plastic box that had enough room for the tiny board I ended up with.

a magnifier is your friend
I have a desk mounted magnifier lamp (which had been in storage unused for 30 years!) and it turned out to be an absolute necessity. Soldering the parts down was surprisingly easy, but working without a design provided the usual set of challenges and opportunities for cursing.

crammed in there
In the end I got it all put together, but I simply could not get it to work. Two days of fiddling, finding mistakes, testing with the scope, trying different computers, and learning the intricacies of rs232 protocols left me no closer to a working cable. In a funk I ordered a USB cable from mouser, and almost gave up.

One final investigation finally revealed the problem. DB9 connectors are number as you look at the BACK not the FRONT! Switch one wire and suddenly the thing works like a charm. One of those things you just need to know.

It is probably the most expensive cable ever built, but I am quite happy with it.

Wednesday, July 25, 2007

down the rabbit hole again

Why is it that every site requires a return to the beginning?
I am working on a new Drupal site for Rae's cousin who runs a small management consulting firm in Seattle.

It should be dead easy, right?
Just drop in a few modules, do some simple theme work, post to the host, and go get lunch.

Instead I am looking for a JQuery plugin that does dropdown menus cleanly, trying to remember if there was a reason I had not used the asset module last time around, fighting with CSS, and generally feeling unmotivated.
I suppose having a well thought out process and a set of standards would help.
Maybe next time.

Tuesday, July 17, 2007


After a few months of research and obsession I bought a scope.
I was getting frustrated with the levitator and thought that having better tools would help.
No, I am lying.
measuring my abilities as an antenna

new toy.  very happy.
Really I just wanted one (and have wanted one for a very long time).
I certainly don't need to prove to anyone what a geek I am, but if I did this would be the way.
For $250 I got a 15 year old tektronixs 2246 from ebay. For those not up on their obsolete test equipment that is a 4 channel 100 mHz scope with built in multi-meter and various other measuring cusors.

With heart in mouth I waited the week it took to get here, wondering the whole time if I had thrown my money away on a door stop. Oscilloscopes are pretty complicated machines, and although I had learned that this was supposed to be a fairly rugged and reliable one, I was sure it was going to be broken. Fortunately it arrived in one piece with all functions seemingly intact.

Now I just have to figure out how to use it.

Wednesday, March 21, 2007

got my blog back!

Somewhere in the heart of the google empire lives an evil gnome whose job it is to make things as complicated as possible.
This malicious individual got hold of my blog, noticed that I had not posted in a year or so, and decided to punish me by making it impossible to log in.
Well I showed them!
After many repeated attempts to gain access with every email address and password I have ever used, and after trying, exhausting, and cursing every help channel they offer (which did not take long).
I finally had a breakthrough!
Somehow my blog had become registered under an email address that does not even exist (to my knowledge), and I only discovered it by looking at the http headers being sent when I tried to log in.

In any case it is fixed now, and I have managed to migrate to the new blogger, and although I may not post for another year, I feel much better!