Author: dmcole | Date: December 30, 2009 | No Comments »
For those of the opinion that I fell off the face of the earth, fear not: I merely got involved in non-electronics, such as dealing with a kitchen remodel and unwell pets.
That said, I also focused a bit in recent months on my Christmas lights show and have documented there a few of the DIY efforts not previously chronicled.
Take a gander at:
Have a happy new year and expect to hear more from the workshop later this winter.
Author: dmcole | Date: July 1, 2009 | 1 Comment »
So, I’m going to use Henne’s transceiver for an LED matrix. You coulda probably guessed, if you’d thought about it for a minute or three.
Henne’s DMX LED matrix schematic (click to download PDF).
Anyway, I fell back on my – ahem – process: first, draw the circuit in Adobe Illustrator and then build it on a breadboard.
(I have been asked in the past why I use Illustrator and not a regular schematic-drawing application such as Eagle or McCad. My first line of defense is the same as when I’m asked why I use InDesign to make slides rather than use the ubiquitous Microsoft PowerPoint: I use the Adobe Creative Suite on a daily basis and am something of an expert with its components. I can create a schematic [or slideshow] faster with the Adobe product than with anything else. Secondarily, I think I get a much better, graphically pleasing, schematic from Illustrator.)
So, there are some changes in this version of the schematic that aren’t electronically or function-driven: instead of the 10-position DIP switch, I have substituted a 2×10 header. This will save only a few cents (around 50) on the bill of materials, but will save some space on the board as well.
These switches signal to the ATMega8515 the DMX start channel to use. They’re set infrequently …
Author: dmcole | Date: June 29, 2009 | 4 Comments »
If you’ve visited my automated Christmas lights page, the letters DMX won’t be unfamiliar to you. For those too lazy to click, it’s an electronic lighting protocol. Two wire. Used extensively in stage shows. And, in recent months, adopted by the DIY Christmas lighting community.
Henne’s DMX transceiver schematic (click to download PDF).
So, I’m working on an idea (I’ll post more when I get closer to the finish) that I want to add to my Christmas lights show, and it therefore needs to talk DMX. Numerous previous postings here will tell you that would mean I’d need to do this on an Atmel chip. Though there are a lot of DMX projects done on Microchips (PICs), fewer have been done on Atmels. And pretty much everyone who has done DMX on the Atmel has based some or all of their work on that of Hendrik Hölscher.
Fortunately for those monolinguists among us, Hendrik – who goes by “Henne” – writes in both German and English. He’s also moderately active on one of the Christmas lights forums.
My initial plans were to write my own code to get my idea off the ground; a few months(!) of fiddling around and I was never even able to pull off my main effect, no less receiving DMX.
During that fiddling, I ran across a web site in Germany that sold …
Author: dmcole | Date: May 7, 2009 | No Comments »
As can be seen from the dates between postings, I took an awful lot of time with this project – and yet, I never really accomplished my goal, which was to have five LEDs independently fading in and out like a candle, driven by an Atmel ATTiny13.
ATTiny13 drives 5 LEDs; programming/test circuit (click to download PDF)
I spent a lot of time with some code that had been created for a Microchip PIC12F675 but it turned out that it was merely random on-off, not fading the way a flickering candle operates. I then spent some time with a second code set, also for a PIC12F675, that did fade nicely, but which had a problem with brightness that I was never able to rectify (it is a duty-cycle issue, I know; I just don’t know how to fix it).
But that second code set did point me in the direction of how to control individual LEDs while within a loop, using bitwise manipulation.
I decided on Sunday that I had a few hours to work on this project and I wanted it finally finished. While the result is not exactly what I wanted, it will suffice.
What I’ve built is a group of four LEDs that fade in and out in an inverse manner. While LED1 fades in, LED2 fades out and LED1 and LED3 work in synch, as …
Author: dmcole | Date: March 13, 2009 | No Comments »
If you’ve visited my web site on backyard railroad illumination, you know about my fixation with creating light that flickers as though it were a fire (either from candle or a fireplace).
Schematic of circuit to fade, flicker single LED (click to download PDF)
The first solution to that problem was to modify LED tea candles — readily available at crafts stores and even Walgreens — so that they would work off of standard 12-volt garden lighting (aka: Malibu lighting).
The dirty little secret of that method is that all the tea candles flicker at the same time. I’m not quite sure why this is so — perhaps the proprietary microcontroller used in those devices is time based and since they all start at the same time, they seem to work in synch? In any event, it does make looking at all the “fires” on my layout pulse at the same time.
So, in the back of my mind, I knew I wanted something besides tea lights to make flickering light on the layout. I kept looking around the net, and in January a reader of the backyard illumination site pointed me to an Instructables that showed a circuit to increase the current that could pass through a tea light, allowing up to four LEDs to be driven in the circuit.
The Instructables …
Author: dmcole | Date: March 7, 2009 | No Comments »
In 2007 I played around with the PICAXE, a microprocessor sold by a non-profit in the United Kingdom that comes loaded with a BASIC-like interpreter (you can read more about it here and here). I built some lighthouse beacons and a railroad crossing light using the device. It had one drawback: I had to write the code and program the chip using, sigh, Windows.
Sample schematic to connect ATMega8 to 6-pin ISP (click to download PDF)
In 2008 I learned a little about Microchip’s PIC series of microprocessors because that was the favored chip by most of the developers in the DIY Christmas lighting world. Though I didn’t actually program PICs, I did learn how to burn HEX code into them using an ADM programmer. These too, had a drawback: you had to write the code and program the chip using, ugh, Windows.
Along the way, though, I heard about the AVR series of chips from Atmel Corp., which had a distinct advantage over PICAXEn and PICs: there was a small community of people who used Macintoshes to make them go. There was a full tool-chain for programming in C (a language I had no experience in) and there were USB devices that allowed for burning the code. Well, hello, sweetheart.
So, somewhere along the line in 2008 I bought myself …
Author: dmcole | Date: March 3, 2009 | No Comments »
It isn’t that I was dying to have a blog — in fact, I’ve tried to stay away from blogging for years.
A few months back it became clear that this electronics thing wasn’t going to go away. I was, in fact, going to be building more circuits over time and perhaps even designing them. I had chronicled the lighting of the backyard railroad at 45mm.com, while the Christmas lights project was at PacificaLights.info.
But that scattered stuff all over the map and I didn’t have a good place to put things that fell in between. Plus, I had never installed WordPress and was interested in giving it a try (we won’t talk about the ill-fated, three-day attempt to get Movable Type to work).
Plus, I had all these iterations of the domain name dmcole — so why not use one for its own content?
I don’t expect to post here often; I don’t expect the material to be earth-shattering. I do expect it to be of mild interest to those who are interested in do-it-yourself digital lighting solutions and those who are microcontroller hobbyists.
Now, I’ve set up by blog and I’m ready to go.
Onward.
\dmc
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