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 Multiplexed, Super-long Larson Scanner?
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By: squall_line (offline) on Friday, April 30 2010 @ 11:35 AM PDT (Read 14352 times)  
squall_line

So, we have the Larson Scanner. It's full of back-and forth, uber-bright LED goodness and '80s and '00s nostalgia. But it's also pretty short.

By default, it lights 5 LEDs at any given time (it's set to control the brightness of 4, but the 5th is lit as a tail), to a pre-set brightness using PWM, etc, etc.

Is it reasonable to assume that, with the proper programming and the correct wiring, one would be able to expand the Larson Scanner to, say, 16, 18, or 20 LEDs, and use multiplexing to light up to 5 LEDs at a time without needing to use a larger battery pack or a different chip (just a different circuit board, obviously).

I'm thinking something more along the lines of the scanners on the walls in the base stars, but with single LEDs, rather than full-on LED panels. A nice, 12- to 18-inch long Larson Scanner, but still with only 4 or 5 LEDs lit at a time. Perhaps step up to a Mega, instead of sticking with the Tiny, to get the additional pinouts?

Any thoughts?


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By: Windell (offline) on Friday, April 30 2010 @ 02:22 PM PDT  
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Without extra parts, you can make a larson scanner bigger by putting each of the LEDs off on leads, instead of on the board. Then they could at least take up more space. You can also reprogram the Larson scanner to light fewer LEDs at a time. If yours has the most recent firmware, hold the button at startup for "narrow eye" mode, or solder a jumper across "Opt 1" to make it default to that.

To make it bigger with more LEDs, you don't actually need a different circuit board. We planned for this-- You can do it by combining a few Larson Scanner kits, plus adding some wires, some programming headers, and a programmer. There are four otherwise unused I/O pins (PD0, PD1, PA0, PA1) on each board, meaning that you could teach each of them to communicate with its two nearest neighbors for synchronization, and allow each to manage its nine LEDs, for an arbitrarily wide Larson Scanner.

You could also set up one as the "master" and send out signals on those lines to up to five neighbors to synchronize them. (And, six Larson Scanners could certainly run off one one set of batteries.)

With a 4.5 V battery pack and 9 more LEDs, you could put two red LEDs in series at each LED location on the board, giving 18 LEDs, spaced apart how you like.

Yes, you could also use multiplexing to add more LEDs without adding AVR chips, but you'd probably need to add other chips to switch the current-- so it wouldn't be a savings in complexity.


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By: squall_line (offline) on Friday, April 30 2010 @ 03:16 PM PDT  
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Well, mine USED to have the latest firmware, but it's been since overwritten about a dozen or more times as I've been experimenting with the programming. I've artificially put it into a "narrow eye" mode by setting two of the positions in the brightness array to 0U, so that's already helped get it more in line with my desires. I have the original source code (or, whichever is currently posted), as well as Larson-alt1 and -alt2 that I've been playing around with.

I thought about linking a couple of scanners together, which may actually work out well, as the form factor of the original board is almost perfect for where I intend to use it, but I figured I'd ask to see if I could get away with using a single programmed controller and just add more wiring. Would linked scanners need to all have their own individual power supply? I haven't checked the data sheet on the Tiny yet to see how much power they draw (presumably, at most 2 would be working hard at any given time in a linked config, the rest would be idling waiting to do something).

I'm still up in the air on the next steps I want to take in this whole venture. I might just end up grabbing another scanner kit, a dev board with ZIF socket, some battery packs, and a second ZIF socket to drop into a breadboard so that I can reprogram and experiment to my heart's content.

I'd post pictures of my scanner in action, but it took a tumble last night and knocked one of the LEDs loose (the solder held, the traces held, but the traces pulled away from the board a little). That's what I get for not flush-mounting all 9 of the LEDs (flush-mounted the final 6, since the first 3 were a huge PITA to get standing away from the board at a set length). Oops!


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By: squall_line (offline) on Tuesday, August 10 2010 @ 01:10 PM PDT  
squall_line

Quote by: Windell

To make it bigger with more LEDs, you don't actually need a different circuit board. We planned for this-- You can do it by combining a few Larson Scanner kits, plus adding some wires, some programming headers, and a programmer. There are four otherwise unused I/O pins (PD0, PD1, PA0, PA1) on each board, meaning that you could teach each of them to communicate with its two nearest neighbors for synchronization, and allow each to manage its nine LEDs, for an arbitrarily wide Larson Scanner.



I'm not sure how I missed this paragraph this whole time. Confused

I've been researching I2C, TWI, etc. for the last month or so Eek!, trying to figure out the best way to make an arbitrarily long scanner, and then last night, I decided to use an approach similar to this one.

I came back to the fora this morning to look around and see what was happening in the EMSL world, I re-read this post, et voila! it was right there in front of me the whole time. Rolling Eyes

I hope to have some additional programming and wiring information available on this topic later this week; I wrote up pseudocode already to test this incrementally, so we'll see how it all shakes out. Smile


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By: squall_line (offline) on Monday, August 23 2010 @ 08:15 PM PDT  
squall_line

Finally got my code and wiring working, and I was able to create a Larson Scanner that can be linked to others, with a fairly easy method to link them together and to "terminate" each end.

I need to go through the code and clean it up a little bit, and find a better way to wire the adjacent scanners together, but it's all working now! I've only tested with two scanners linked together so far, but I'm confident that it would work for as many scanners as one can link together and still run on the battery pack.

Once I clean up the wiring, I'll make a video and post a link to it. Smile

Once I clean up the code, I will add it to the Google Code project page.

All in all, I'm pretty psyched! Big Grin


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By: Windell (offline) on Monday, August 23 2010 @ 08:17 PM PDT  
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Sounds sweet! And, if you get it working well and we can reproduce it, we'll post about it on the blog. Big Grin


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By: kavett (offline) on Monday, September 20 2010 @ 10:05 AM PDT  
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Quote by: Windell

...

To make it bigger with more LEDs, you don't actually need a different circuit board. We planned for this-- You can do it by combining a few Larson Scanner kits, plus adding some wires, some programming headers, and a programmer. There are four otherwise unused I/O pins (PD0, PD1, PA0, PA1) on each board, meaning that you could teach each of them to communicate with its two nearest neighbors for synchronization, and allow each to manage its nine LEDs, for an arbitrarily wide Larson Scanner.

You could also set up one as the "master" and send out signals on those lines to up to five neighbors to synchronize them. (And, six Larson Scanners could certainly run off one one set of batteries.)

...



is this done by going one for one on those I/O points IE: PD0 to PD0? PD0 to PA? i currently work for the US Navy and while my experience is at the box level & not a whole lot of the circuit card level, i'm getting into it and this site is FTW / to blame (depending on if you ask me or the wife RazzLaughing Out Loud ). i also have a general grasp of electronics, where pin 1 is and which end of the soldering iron gets hot.

please advise, any help or direction would be much appreciated. any simple books to get to glean more info on the topic?

sorry for the rehash of an old topic and Hello everyone!


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By: squall_line (offline) on Monday, September 20 2010 @ 10:15 AM PDT  
squall_line

Quote by: kavett

Quote by: Windell

...

To make it bigger with more LEDs, you don't actually need a different circuit board. We planned for this-- You can do it by combining a few Larson Scanner kits, plus adding some wires, some programming headers, and a programmer. There are four otherwise unused I/O pins (PD0, PD1, PA0, PA1) on each board, meaning that you could teach each of them to communicate with its two nearest neighbors for synchronization, and allow each to manage its nine LEDs, for an arbitrarily wide Larson Scanner.

You could also set up one as the "master" and send out signals on those lines to up to five neighbors to synchronize them. (And, six Larson Scanners could certainly run off one one set of batteries.)

...



is this done by going one for one on those I/O points IE: PD0 to PD0? PD0 to PA? i currently work for the US Navy and while my experience is at the box level & not a whole lot of the circuit card level, i'm getting into it and this site is FTW / to blame (depending on if you ask me or the wife RazzLaughing Out Loud ). i also have a general grasp of electronics, where pin 1 is and which end of the soldering iron gets hot.

please advise, any help or direction would be much appreciated. any simple books to get to glean more info on the topic?

sorry for the rehash of an old topic and Hello everyone!



To get a master/slave relationship to work for this could be quite time-consuming.

Or, at least, it was for me. It took almost two months of research before I finally settled on my above configuration, which links units side-by-side and allows each one to manage its own LEDs, and start using signals from its neighbors. To go with an addressable serial communication setup was going to be way too time-consuming and ultimately WAY over-kill for what I wanted to do.

Which reminds me... I need to get the videos taken and the write-up done for this and sent in. Very soon, I hope! Stay Tuned!


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By: Windell (offline) on Monday, September 20 2010 @ 10:46 AM PDT  
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I finally settled on my above configuration, which links units side-by-side and allows each one to manage its own LEDs, and start using signals from its neighbors. To go with an addressable serial communication setup was going to be way too time-consuming and ultimately WAY over-kill for what I wanted to do.

I'd tend to agree; bit-bang serial is terribly time consuming, and a sync pulse should be sufficient if you know what each side needs to do.

squall_line: It's almost October-- we'd love an excuse to do a Larson Scanner post next week!


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By: kavett (offline) on Monday, September 20 2010 @ 12:37 PM PDT  
kavett

so how would i go about doing the a fore mentioned linking to link two larson scanners together? 9 LEDs just isnt enough! if only i could say it in a cristopher walken voice "it needs more LED".

can it only be done through programing of the chip or can it be done with the currently programed chip in the kit linked to other kits?


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By: Windell (offline) on Monday, September 20 2010 @ 12:42 PM PDT  
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can it only be done through programing of the chip or can it be done with the currently programed chip in the kit linked to other kits?

This is a new program, so it would have to be changed through a programmer. If the code works well and is otherwise backwards compatible, we could make it the "standard" firmware at some point in the future, though. Big Grin


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By: squall_line (offline) on Monday, September 20 2010 @ 01:07 PM PDT  
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Aye, it's a new program, indeed, although based on the original program.

I'm still trying to work out ways to make it more user-friendly and more backwards-compatible, as I changed the output method to run the LEDs off the edges, rather than overlap when they bounce back (the run-off code is posted on the Google Code page already), and I'm still trying to figure out the best way to allow speed changes to happen, since I didn't link the stock button wiring between units.

I'm getting mission creep/feature creep, I think, and trying to ward it off to the best of my abilities. Oops!


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By: squall_line (offline) on Tuesday, September 28 2010 @ 08:05 AM PDT  
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Well, I added and then deleted some features, and cleaned up the code a little bit, as well as adding a crapload of comments in the code itself.

I've taken some pictures and I'm in the process of annotating them and doing a brief writeup, though I want to clean up some of the wiring to make it look a bit more presentable. I should have something turned in tonight or tomorrow night!


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By: Anonymous: jbisjim () on Monday, October 11 2010 @ 02:28 PM PDT  
Anonymous: jbisjim

its october

looking for the super long LS..





       
   
By: squall_line (offline) on Wednesday, October 13 2010 @ 01:17 PM PDT  
squall_line

Quote by: jbisjim

its october

looking for the super long LS..



Ask, and ye shall receive:

http://www.evilmadscientist.com/article.php/laaaaaaaaaaaaaaaarsonscanner

Enjoy!


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