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Building Your Own Glowing Cyber-Balls?
krezel asks: "So I've been drooling over the Ambient Orb, a cool little gadget 'glowing ball' that you changes colors based the 'health' of things you specify. It can do stuff like fade from red to yellow to green as your stock portfolio improves. However, being a poor college student I can't afford its $200 price tag. I've found lots of sources for super bright multi-color LED's. Cast a couple of them in some translucent resin, hook them up to a power source, and you've got yourself a cheap glowing ball. But I've yet to find any good information on how to build hardware that will let me control relays for devices like this through my serial or parallel port. Basically I'm looking for a cheap way to build a board that will let me control 4-8 relays (for each color) over my serial port, and some info on how to write the software for it. This could be a very cool project, and I plan on making the plans available, and the code Open Source, when I'm done with it. Any ideas?"
But seriously, I've always wanted something like this for work. A simple status indicator whether the cluster of machines I'm responsible for is Working Fine (green), Having Issues (yellow), or Completely B0rked (red).
Currently, I keep a persistent browser window open to a simple web-based script that checks on the status of everything and sets its background to one of those colors based on what it finds (it's quite a bit more verbose than just that should something be wrong, but that's not the point). This is fine and dandy for my use, but for the sake of being interupted during an emergency...
It'd be really cool (and actually useful) to have a separate orb that glows the same color... so the next time my PHB runs in to tell me I forgot my TPS report cover sheet.. er.. to tell me that he's noticed a problem with the site, he'll first see the big red glow and realize I'm already aware of it.
(that, and when I'm deep into a Quake match, and can't see the little window...)
All you need are the following:
1) 25 PIN MALE DB Connector (like would plug into the parallel port) - OR, probably easier, grab like a 6' or longer 25pin Parallel Printer or extension cable and chomp the end which doesn't plug into the computer off.
2) 8 superbright leds.
3) 8 10K resistors.
4) 8 2N2222 or other NPN transistors (Just go to radio shack and get a bulk package of "NPN switchint ransistors")
5) 8 "smaller" resistors. Like roughly 500 ohm, but be prepared to experiment with the value. Lower value=brighter, but if you go too low you will burn out the LED. There *IS* a formula for the smallest permitted value. I won't go into that here.
6) Perfboard to put it all on
7) 9 or 12V DC wall-mount supply (or similar).
A little background:
The parallel port on the PC has 8 outputs, on pins 2-9 of the 25 pin connector. The ground for these are on pins 18-25.
You can technically get away with just wiring the led directly to an output port, then to a resistor which then connects to the ground. Google for "parallel port led"
However, it is likely that you will need more current than the parallel port will provide. For this you can use a transistor to act as a solid state switch.
Here's a description of the schematic:
For each output pin:
1) Wire the output pin on the parallel port to one side of a 10K resistor.
2) Wire the other side of the 10K resistor to the base pin on the transistor.
3) Wire the emitter pin on the transistor to circuit ground.
4) Wire from the collector pin on the tranmitter to the pin closest to the "flat edge" on the LED.
5) Connect the other LED pin to the "smaller value" resistor.
6) Connect the remaining pin on the "smaller" value resistor to the + wire of the power supply.
ALSO, do the following:
1) Connect the ground pins (18-25) of the parallel port connector to the "circuit ground" mentioned above.
2) Connect the "-" wire of the power supply to the "circuit ground".
You can test this before plugging into the computer by plugging the DC adapter in and then jumpering between the + wire of the power supply and each output pin on the cable you are going to plug into the computer. The corresponding LED should light.
I'd recommend just doing the first led first to make sure everything works.
NOTE: YOU CAN BLOW OUT THE COMPUTER PORT IF YOU DO THIS WRONG. I HAVE NOT CHECKED THE ABOVE DESCRIPTION SO IT MIGHT BE WRONG AND MAY CAUSE THIS EVEN IF YOU FOLLOW THE INSTRUCTIONS EXACTLY.
If you need more LEDS on a given output (like 2 or 3 to get enough light), you can just connect a LED/resistor pair in parallel with the existing one (all of the LEDS are connected to the transistor, all of the resistors are connected to the + power supply connection, and each led is connected to it's own resistor).
You basically drive this by outputting data to the parallel port. You output a single byte at a time - the most recent byte is what the leds are set to on or off.
If you want to vary the brightness of the LED's you can actually do it by turning them on and off quickly in software. A simple timing loop which have the leds on 50% of the time would result in the leds being 50% dimmer than if they were just left on. Of course you have to do this fast enough so they don't "flicker" or blink.
Win 9x has direct access to the ports. Win NT/XP needs you to go via the device drivers, but it's not a difficult problem - plenty of info for how to do it.
:-)
Beyond Logic
Parallel Port Central
Both the above have a bunch of useful stuff.
Also don't forget that you'll need to learn how to drive LEDs. I'm admin on an electronics board, so here's a blatant plug:-
BasicElectronics board, LED FAQ
(and kudos to David Bridgen and MacGregor who put that info together
Grab.