I would be wary of using a jigsaw on small PCBs (under 8"x8" - yeah, I know it ain't metric), unless you have a way to support and clamp it while you cut it; otherwise it doesn't seem too safe.

For smaller PCBs, as well as really small and intricate cutouts, the best thing to use is scroll-saw:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93012

...which is a machine meant for such work. Unfortunately, a good one (cast base and table) can be expensive (note: the one I posted I don't consider worth a hill of beans; it is for illustration only). It's worth finding one, though, if you can - the heavier the frame, the easier the cuts will be, plus less vibration.

Harbor Freight sells a small 4" table saw, for those with cramped space:

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=93211

[briza]

I contacted a former coco programmer letting him know about this artifact mode and the possibilities it has. Mr Dekok ended emailing me back saying it was about time people looked at this quirk in the Gime chip, As he played around with it back in the late 80's or early 90's but never did anything with it as back then most users were using RGB displays.

Nice to see you here, too, briza - I hope you joined because of Arduino, and not just this post! One of these days, I plan on hooking my Arduino up to Roger Taylor's CoCo3.com RS-232 pak (I got the "Hacker's Special" a while back, but have yet to put it together - it came unassembled, without a cartridge or the bluetooth module; the RS-232 output though, IIRC, is TTL - so it should be able to communicate with an Arduino easily).

The thing about the CoCo 3's "high color" artifacting mode is that in a way, it was discovered. There was an article in the Rainbow about how to use it; that's what I played with. But it was published as a means to get a few extra colors on the high-res (640x192) screen, which could only officially use four colors from the palette of 64 - the article detailed how you could get several more, as long as you used a composite monitor or TV. From playing with it, you could only get so many extra colors, something like 8 or 9 dithered colors.

No one - except perhaps for your programmer friend - ever thought to use the four grey scales available on the CoCo 3 in that mode, dithering them, to cause artifact colors. I must say it seems tragic that your friend didn't attempt to publish the method to the wider public; even a simple letter to the editor of the Rainbow would have been sufficient. Instead of it laying dormant, perhaps those games and other applications that could've taken advantage of it would have been written. History is history though, unfortunately.

I am still uncertain, though, whether this method is the fabled "256 color mode" Sockmaster and others have been pursuing off-and-on for years; it doesn't seem to match up with what has been discussed and noted (no strange twiddling of the GIME registers or such). Even so, it was definitely a very obscure mode. I am hoping Roger Taylor takes advantage of it with a new game!

 

One of the more surprising chips ever had to be the GIME chip used in the Tandy Color Computer 3; we're still learning about it. It is unfortunate, though, that it was a very proprietary chip, that was only available to Tandy for the Color Computer 3 (it wasn't sold to 3rd parties). Furthermore, with it being a tricky beast, emulation of it is difficult - the information that is available is what certain people have reverse engineered, plus what was known from service manuals and the like from back in the day (the design materials are long gone).

For instance, back in the late 1990s or early 2000s (I forget which), there were rumors floating around about a mysterious "256 color" mode on the Color Computer 3; this on a machine which officially had only 64 possible colors! The rumor was spurred on by an individual who claimed to have seen it when they worked at Microware, and that it involved some trickery with certain registers.

People played around with this thing forever, to no avail. There had been other methods used to get many more colors on the display than what was officially available; many involved high-speed assembler being used to change the palette rapidly during a horizontal blank, as well as the vertical blank. An early "hack" enabled the ability to see all 64 colors on-screen at once. Other "hacks" allowed still images to be displayed that had thousands of colors. Nothing quite as impressive as the Amiga's HAM and HAM-E modes, but then again this was being done on a 2 MHz 8-bit CPU...

Another method back in the day, when the Rainbow Magazine was being published, used the composite output or NTSC output to a TV to get more colors on-screen via dithering four colors in the 640x192 mode on the Color Computer 3. Little did anyone know at the time how close they were to discovering an amazing mode. I played with it myself, and it never occurred to me or anyone else.

You see, back in the early days of the original Color Computer, there was a display mode (the highest resolution mode on that machine) of 256x192 pixels, 2 colors (black and white; well actually something close to white called "buff"). When displayed on a television, and placing alternating pixels of black and white together, you could get other colors of red and blue, due to NTSC artifacting. Many games utilized the mode; most had a method where you had to hit reset multiple times to get the order of the colors to switch, in order for the game to have proper colors. What you lost was resolution (the resolution effectively became 128x192), but the gaining of colors in the mode was a popular tradeoff.

On the Color Computer 3, that was how it was recently (late 2009) discovered that one could get 256 colors! By using the 640x192 4 color mode on a composite monitor or television, and using a palette of black, dark gray, light gray, and white, while alternating the pixels properly, the NTSC artifacting takes over; you end up with a 160x192 256 color display.

People have converted various images to the dithering patterns necessary to display them; while I haven't personally seen a real image yet (I don't have my Color Computer 3 system set up currently), the digital photos taken of composite monitors have been amazing to see; they say the actual images are even better. While I have found this to be an amazing discovery, it will always be on my mind as to "what if" it had been discovered back when the system was being sold at Radio Shack (1986-1991).

Ah, well...

 

I bought it from a mac collector a little while back for a song and a dance, I never personally owned one when I was a kid we had a IIe, but I always liked the looks of the IIc better + its small which is nice when in storage (its just barley larger than a typical laptop)

Yeah, I had a friend who had one back in high school; seemed dinky compared to my TRS-80 Color Computer (not as small as a Timex Sinclair 1000, though). Of course, on the Color Computer end, we had the MC-10...

Its too bad you can't find any of the old school display chips; many of them would be nearly perfect for the Arduino (parallel addressing and data bus aside, of course).

 

the ram is important for me to learn considering I am doing a 100% restore on my 1985 Apple //c (rom2) and the thing has 128KB of it, along with its pretty easy to upgrade in the future outside of my nostalgia as parallel ram has not changed much

You're restoring an Apple //c? What happened to it that caused it to stop working? I find it curious; I have a couple of //gs boxes in my shop that work fine (well, last time I played with them, which was a while back).

Now my Altair - that's a beast of a different color; that thing's going to be an absolute bear to restore when I get-round-to-it. As far as I can tell, it sat under a pile o' junk and has more dirt in it and such; ugh. Getting the power-supply up and running (without exploding - it likely needs new caps) will be the first job...

Good luck on your project; it sounds like a fun a thing to try a hand at. I know when I get around to working on my Altair, I might try building a TV typewriter for an interface to it (I have a copy of the "TV Typewriter Cookbook" - so it shouldn't be too difficult, outside of sourcing the components).

 

[Osgeld]

What are you thinking about trying, Osgeld? External clocking multiple ATMegas? True random number generator? Clock signal injector? S&Gs?

 

[edit]I still think one of those automatic SMD tweezers will be able to identify the parts[/edit]

Something like that would be helpful; there also appears to be a few project blogs out there detailing how to build such a set of tweezers for an auto-ranging multi-meter:

http://www.maxim-ic.com/app-notes/index.mvp/id/4459
http://poeth.com/SMD.htm

They would at least give values (and types?) for "unknown" parts, which may be enough for most uses.

Anyone have any tips and tricks for component IDing?

Something to keep in mind, which has always been done in electronics for a number of years, is the concept of "house markings".

What this means is that a company making a board will have the company making the components put part numbers on the parts that match up with a reference that the board company has, but doesn't reference to anything that you or I have access to. Many time, when these companies go "belly up", the surplus goes to surplus dealers who will sell "NPN transistors - house marked" - but you have little to no idea about any performance numbers or whatnot to tell you whether they will work in your application.

There is almost no way to get at those cross referencing data, either. Even if the company is still in business, they won't give you any of that data - its a way of making the board a "black box" to prevent competitors from reverse engineering a device (not that it really stops this, but in the business world, they think it does).

I wouldn't be surprised if SMT parts were done the same way - in fact, it is probably cheaper, since there no way to mark them anyhow due to their size, and they come off a tape/reel which is ordered - if you're lucky, there's polarity markers on the ones that need them...

Since in SMT work, a transistor can look just like a regulator, and a capacitor just like a resistor and an inductor - if there aren't any workable markings, you are probably hosed, unless you have access to a variety of test equipment and know how to use it. But this method is time consumming; ultimately, it would be cheaper to just buy the parts, so you know what they are, and what their spec is.

I'm not one to really talk about on this subject, as I am no where near to that level (nor do I have the desire; way to many other things on my list), but...

1. I think you would do yourself a favor and study what other people have done; just pick a different processor outside of the family to study what they did, to apply the principles to your effort (even if it has already been done before). For instance, find out how the Arduino was ported to the ATMega1280 or something, then apply those steps to the ATTiny processor you are targeting.

2. Study the datasheets like a fiend.

That would be how I would approach it if I were to take on a project like this. It sounds like you are in for a wild (and possibly hair-pulling) ride! Good luck with the effort!

 

Ubuntu 9.10 64-bit - I moved to the Arduino after finding I couldn't get the Parallax bytecode "compiler" to work in 64-bit (the compiler was binary only, and statically linked to other libraries in the system - Parallax had lost touch with the developer of the Linux kit, and they didn't have a copy of the sourcecode - so they lost me as a user).

This machine is currently in my office.

I am in the process of building a machine for my workshop and bench; it will likely also be Ubuntu (or I may try something else), but it will likely be 32-bit as all the processors/boxen I have in my junk pile are 32-bit. What I am aiming to use for this box is an old iCue BookPC, hopefully with a 1 GHz+ Celeron and as much RAM as I can stuff in. I am also hoping to hack it to allow for a serial port in addition to the USB, but I am still researching that option (supposedly it is possible, in some manner - there's supposed to be pads on the mobo for a serial port somewhere). It does have a parallel port, though!

 

I suppose that was an appropriate "bar post"!

 ;D

After I wrote my article and found the Discovery Spark, I went to Amazon and purchased one, as well as an OWI-535 Edge.

Well, they arrived today.

First impressions, based on the unopened boxes?

OWI-535 Edge: The box is fairly large, and the packaging is well designed and fairly eye-catching. It reminds me of a Lego kit.

Discovery Spark: Still ugly as sin for a robot arm, but what caught my eye first was the shape of the packaging; if you've ever seen the original packaging of a real Armatron, you know it is about the dimensions (maybe a little larger?) of a concrete block (8"x8"x16"). The box that the Spark came in does not look like it could hold an Armatron - unless they have made it with a removable base. If you have ever taken an Armatron apart, you know about the complex interior gearing system...

I intend to take some pictures of both of these items and put them on my site, hopefully this weekend. I will likely do a side-by-side comparison with one of my other Armatrons; I might also introduce the Armatron I intend to convert to computer control at some point. For the Edge, I am thinking about doing an assembly article, and perhaps implementing computer control of it using an Arduino (yes, I know it has been done already).

We'll see how things go, as I find the time...

 

All - I just wanted to let you know about an archive I just released on my website, which includes articles and information on interfacing the Armatron to a computer (or a microcontroller, like the Arduino); it can be found at:

http://www.phoenixgarage.org/show_article/92

In addition - if you are looking for an Armatron to hack, I just found out that Discovery re-released it as the "Spark":

http://www.phoenixgarage.org/show_article/93

I hope that the archive will help somebody out there, or at least give them some inspiration!

 

I was thinking of a small IR/LDR based intruder alarm (kids will have fun putting it up in their rooms) any other such suggestions which kids can relate to and apply in their own worlds?

This reminds me of a project back when I was in grade school (5th grade); my friends and I were constantly missing things (pencils and paper, mainly) from our desks (assigned seating, old-school lidded desks), we suspected the teacher.

I ended up rigging an alarm using my 150-in-one kit from Radio Shack and a custom trip-wire like switch to the desk lid; it could be turned off if you knew what to do by carefully openning the desk, reaching in, turning it off with another switch.

Imagine our surprise when, during recess (do kids even get recess anymore?), the alarm sounded very loudly and our teacher ran out calling my name to come shut the thing off. I turned it off, looked at her, then went back out to recess. No other words were exchanged that I remember.

I was never sent to the principal.

Our desks were not messed with the rest of the year.