Tuesday, November 22, 2005

Computer Setup

When building electronic projects, it's sometimes nice to have a PC around - for looking up datasheets online, pulling up schematics, or even for providing I/O while testing a circuit. My recommendation for a machine would be to use an older computer with a Pentium II 233 or so processor and as much RAM as you can cram into it. The older machine is nice in that it is fast enough for most simple things that it will be used for on a bench, but old enough that it can support all sorts of old cards and should have most of the "legacy" ports built into it.

These "legacy" (I hate that word - these are such good ports, they're just old - call them classics or something) ports are the standard parallel, serial, and MIDI. The parallel port, which long-time readers of this blog should know is my favorite, provides 12 digital output lines and 5 digital input lines. The serial port is another handy one which provides a TX (transmit) and RX (receive) line which can be used for programming, data-acquisition, and other similar uses. The unsung hero in my opinion of these classics is the MIDI port which provides 4 analog inputs which are each converted to an 8-bit value and 4 digital inputs.

In addition to ensuring that these ports are present, the machine should have a network interface card (NIC) if you are planning to get online, or at the least a modem and a phone line. It might also be wise to look for some of the older ISA cards that are available that provide extra ports and connectivity - check eBay, local auctions, or old computers that people might be willing to part with for these.

For software, I would suggest running either Linux or a version of Windows prior to Windows 2000 - Windows 98se is a good choice as it is the latest version before 2000 that isn't ME (I would advise no one to run ME...). The old versions are suggested because the versions of Windows that are NT based have security to prevent low-level access to the hardware ports. Also - it's nice to run real DOS sometimes for older applications and command-line based programs that you might write. Linux is also a very nice choice since it is so open, easy to program for, and lots of people who do hardware work run it.

Programmable Integrated Circuits

A highly useful component for all sorts of projects is the Microchip brand PIC (programmable integrated circuit). The chips contain a microcontroller, some RAM, and some storage space (quantities and speeds depend on the particular model). Basically - one chip can act as a tiny stand-alone computer with inputs and outputs for controlling other circuits. Most are programmable in-circuit allowing for updates to the code that is run. To program one, you will need to build or buy some sort of PIC programmer (specifics again vary by model of chip to be programmed). You will also need some software for compiling code (unless you want to write assembly - your choice!) and sending it to the PIC. Microchip itself provides a free integrated devolpment kit (IDE) called MPLAB that works very well.

If you are having troubles coming up with uses for this highly versatile devices, there are many ideas and projects out there. Good luck!

Thursday, November 17, 2005

Etching a Circuit Board

You've got a circuit that you've prototyped on a breadboard, built using perfboard, and now you want something a little more professional to sell/give away/use/whatever. Or maybe you don't. Either way - you might want to take the next step with a good circuit and etch your own circuit board. This makes construction easier, the circuit potentially more compact, and it looks a lot nicer to boot. There are a few different ways to go about making the board - the most common is to apply some sort of a mask to a copper-clad board and then soak the board in a solution that dissolves the non-masked copper. Laying out the mask can be done by hand with a resist-ink pen (RadioShack sells a decent kit for doing this), ironing on a printout from a laser printer, or by using a special photo-resist board.

Another method which is somewhat popular (but much more difficult) is to make (or buy) a computer numerically controlled (CNC) mill. This is basically a drill press that has some method of either moving in two dimensions or moving the board in two dimensions that is controlled by a computer. This allows the piece to move past the drill bit, which is controlled vertically by the computer. If the bit is just below the surface of the piece as it is moved, a line will be cut out of the copper cladding. If the piece stops and the drill bit goes down, a hole is drilled through the board where a component will go. This whole setup, while complicated, allows for nearly complete automation of the process and can produce very nice boards.

Thursday, November 10, 2005

Computerized Christmas Lights

Yup, you heard (read?) right... computerized Christmas Lights! Why? Why not?! The last two Christmas seasons I have gone to see a very interesting light display in Winona Lakes that was put together by one of their Computer Science professors. It consists of a lot of strands of christmas lights - some on trees, but most on a large conical "Christmas Tree" that is against his garage. All of the lights are controlled by a computer running Linux and some custom software (actually, custom programming language - the guy is a CS prof...) that controls when the lights are on and off, which allows the tree to change colors and display patterns. All of this is set to music that is broadcast via a small FM transmitter, so you can tune in on your car stereo to hear it.

This got me to thinking about how cool it would be to build my own version, on a much smaller scale at first. I looked around and came across a website that dedicates itself to and calls itself Computer Christmas. The layout leaves a bit to be desired, but there are plenty of circuits and great ideas available. This circuit provided the inspiration for me to begin putting my own together using twelve of this circuit and the twelve output lines of the (wait for it...) parallel port. I've had all of the parts ordered since summer and have just been working on getting around to putting them all together. This is where Monday's post comes into play - the boards that they sell work with the parts I already have, making assembly very very easy.

So - be watching for further updates on this project, and hopefully around Christmas time some pictures/videos of my light display.

Monday, November 07, 2005

Great Site with (sadly) Only One Product

I was researching some equipment for work and came across www.simpleio.com which has an opto-isolated triac board that they sell in various different forms. First - there is a version with eight triacs and another with four. They also sell the same boards without terminal connectors for a substantial saving, kits that can be assembled (with and without terminal connectors), and just the bare boards that can be populated with your own components. As if this weren't enough - they also have the schematics and board layouts available to download for free! But wait, there's more! There's also a section with details about how the circuit and the individual components work. The whole feeling of the site can be summed up quite well in this from the schematic page: "I hope you like this enough to buy the boards (the triac output bare boards are fun!), but even if you don't buy from us, you may know someone who will." This looks to be an excellent site and I plan to purchase some of their boards for my own use - more on that later.