The Tunnel of Questionable Enlightenment!

[ismist]

just getting excited to see all yer hard work out there, and of course playing some breakz for the tunnel party on the playa. awesome work justin

[Workinonit]

I managed to get up to 40 arches working but the whole system is locking up very frequently at that distance. But this is why we did it 2 weeks before we have to leave. You do full set up to find the problems here and not on the playa. Several ideas have been thrown around and we ARE going to fix it!

I spent the better part of a couple days on what turned out to be a rather silly problem. I just felt the need to hijack your thread to vent!

I'm using a PIC microcontroller to drive a chain of LED drivers (PCA9922, shift-register-style drivers with 1-resistor current setting). I started using the PIC's synchronous serial port feature for the first time to shift the data out, and I was getting bizarre results. I surmised a clock problem, but couldn't really decipher it as it was spurious and weirdly effected by oscilloscope probes. I barked up the wrong tree for a bit concerning the duty-cycle (which, on the PCA9922 spec sheet expects 40% to 60% although it can handle "0 to 25MHz".) Nonetheless, I finally determined that it must have been some RF noise as a capacitor rounded off the clocks enough to work perfectly. Well, sort-of ... it _works_ at least.

The project is a sick bit of elegance that should let me drive 50 (or more) RGB LED's (150 emitters) with 8-bit pulse-width modulated (PWM) resolution from a 20MHz-clocked PIC. And then do animation and processing on the side. I'm using a technique called bit-modulation for PWM which disassembles all the PWM values into bits, sets the shift registers to turn on all LED's with bit 7 set, sets all the output-enable pins for 128 cycles, then moves to bit 6 for 64 cycles, bit 5 for 32, and so-on. The effect is that over the course of 256 cycles, each LED is on for its PWM value's duration, except the processor only has to do heavy computing 8 times per those 256 cycles. I cheat a bit and don't get to 100% brightness because of fixed delays between cycles and such, but it's accurate enough.

Have you tried looking at the FastSPI_LED library? That is what I am using, but sounds like you went ahead and customized for your own application.. It does bit banging to do the PWM. However, the LED strips I am using do their own PWM so it takes all the processing off the driving processor. Look for LEDs with the TM1801 or WS2801 pixel controlers... Also recently heard about the Wixel, new controller chip... have not had time to check it out but sounds like a promising bit of technology for this type of stuff. You can look at this doc http://www.nxp.com/documents/data_sheet/P82B96.pdf for some help with you capacitance issues. Might be good enough for you to just make sure you have the max pull up resistors on their or put those linebuffers/repeater/etc in the mix. Granted those buffers are for I2C but I believe they would work with any bus meeting the spec for it. Bought some zeners for my project to protect from the dry staticy playa, but alas I don't think I have the time to install them.... hopefully there is enough protection in the chips... Good luck sir!

[Workinonit]

Its been quite an emotional roller coaster the last 3 days! I have spent every waking and likely non-waking hour working on the project to work out the kinks. I had yesterday afternoon resigned myself to do something like 38 arches because I could not get anything to work very reliably beyond that point. Things were looking grim. Half of the arches were locking up terribly and nothing I did fixed it. Well, I managed to figure out why half of it was working and the other not. Slowed down the I2C bus to just 5khz (surprisingly this is enough to update all the arches 20 times per second!) and voila! And, now 40 arches are working very stable now! But now I am going to put in just one more day to see if I cannot get everything worked out for the remaining 20 arches working. If not, it will just be 40 arches but its going to be spetacular any way you look at it!



Wish me luck! And see you out on the playa!

Oh yeah and sometime between now and Tuesday I need to pack and prep for Burning Man!

[TailsCut]

Can't wait to check out the result of all your hard work!

[Zhust]

Have you tried looking at the FastSPI_LED library? That is what I am using, but sounds like you went ahead and customized for your own application.. It does bit banging to do the PWM. However, the LED strips I am using do their own PWM so it takes all the processing off the driving processor. Look for LEDs with the TM1801 or WS2801 pixel controlers... Also recently heard about the Wixel, new controller chip... have not had time to check it out but sounds like a promising bit of technology for this type of stuff.

I've seen the PWM LED drivers and they're pretty cool for the most part, but many require one resistor (or two) per emitter, and the cost is quite a bit higher. The PCA9922 chips cost about $1 each, the boards are $2, and the LED's are $1 each, so a populated board has 5 RGB LED's and 2 PCA9922 chips so it costs a bit more than $9 or so or about $2 per LED.

You can look at this doc http://www.nxp.com/documents/data_sheet/P82B96.pdf for some help with you capacitance issues.

I'm watching 50 LED's work right now next to me with nearly perfect consistency, so I think my clock problems might be okay (I wired the boards together with CAT5 cable and supplied 1 ground twisted-paired with the clock and a second ground twisted-paired with the data which I think helps too). Not as pleased with AdaFruit's LED's because I have about 5 failures already ... grr ...

Good luck sir!

You too! I hope both our projects make it to the Playa successfully!

[Workinonit]

Holy crap! I did it!



See you all on the playa! @The Tunnel of Questionable Enlightenment 10pm on Wednesday!

[MyDearFriend]

Oh man (((Workinonit))) that is so AWESOME I am so impressed and so excited to see this!!!

[junglesmacks]

Oh man (((Workinonit))) that is so AWESOME I am so impressed and so excited to see this!!!

+100!!

See you out there on Wednesday night. I've got it marked in my book..

[Zhust]

Holy crap! I did it!

Fantastic! I hope to stop by with a much more modest LED coat!

[Fire_Moose]

Bump!

This thing is epic, sorry I'm going to miss seeing it on the playa.

[Foxfur]

CFM, Mr. Five, and I rode out to the ToQE on Saturday night before opening. I walked up to a gentleman who was at work soldering and asked him if he was on eplaya. He said yes, his name was Workinonit! I asked him if he'd ever heard of Foxfur. He screwed up his face, thought about it, and said he'd never heard of him, Bwahahaha! I told him Ff's a pretty cool guy but a bit of a spaz and then introduced myself as CFM!
What a fuckin blast.
I enjoyed the hell out of the tunnel. Very well done! Thank you!

[Workinonit]

CFM, Mr. Five, and I rode out to the ToQE on Saturday night before opening. I walked up to a gentleman who was at work soldering and asked him if he was on eplaya. He said yes, his name was Workinonit! I asked him if he'd ever heard of Foxfur. He screwed up his face, thought about it, and said he'd never heard of him, Bwahahaha! I told him Ff's a pretty cool guy but a bit of a spaz and then introduced myself as CFM!
What a fuckin blast.
I enjoyed the hell out of the tunnel. Very well done! Thank you!

Well now I have and idea who FoxFur is!!! I hope I was not too grumpy. Things were not working so great that night! So happy you and so many others enjoyed the project. Now to motivate to work on it. I hope to fix the communication problems and get all 60 arches working. Hopefully that won't take much time and I will be able to implement all the new ideas I have for it for next year! I think once I can get the arches solid, that the controls will be the next refinement. LCD displays with variable values and such to inform people when what they are doing is making changed and when its not... plust some more buttons, sliders, etc...
As always...
Workinonit!

[Workinonit]

I have set up a Flickr group called The Tunnel of Questionable Enlightenment. I would love to see pictures and videos of the project posted here to share with everyone!

http://www.flickr.com/groups/1739433@N24/

Thanks for all your support! Already thinking of how to fix the issues we had this year and want to really focus on the controls for next year. OLED screens to show variables and which patterns do what. Gonna fix all that locking up too! Going to either daisy chain the strips or perhaps linking them all through WiFi or a 2.4Ghz wireless network! Anyone with experience in either of these areas on the playa that can offer advice or problems encoutnered would be much appreciated!

Will be submitting a grant proposal this year again... we shall see how we fair after this years performance!

[FIGJAM]

Are you taking it to AZDC?

[ibdave]

Hey Hey Hey,
Great Project and many thanks..
I chatted with ya for a brief moment as you were doing a repair in the dark and I held my light for ya..
(you weren't happy, mutterings about fucking not respecting art)(your so right)
I told ya about me helping Mark Lottor out and you perked up and really hopped to meet him.. Did ya?
I still have his email if you need it.. send me a PM.... Great Project and can't wait to see what you create next...

[Workinonit]

Are you taking it to AZDC?

I cannot make it to AZDC this year ;(

Been thinking about bringing 20 arches to Aftermath though...

It will definitely make a showing for Saguaro Man though!

[Workinonit]

Hey Hey Hey,
Great Project and many thanks..
I chatted with ya for a brief moment as you were doing a repair in the dark and I held my light for ya..
(you weren't happy, mutterings about fucking not respecting art)(your so right)
I told ya about me helping Mark Lottor out and you perked up and really hopped to meet him.. Did ya?
I still have his email if you need it.. send me a PM.... Great Project and can't wait to see what you create next...

thank you for the kind words! It seemed to be very well received even though it had to be scaled down and was not working properly in my eyes (even though most people did not notice or care!).

Yes...its a love/hate relationship to bring art to the playa! The project managed to stay mostly working by the end of the event! I am quite happy for this!

I went over to the Cubatron portal and managed to find Mark and thank him for his inspiration. It was quite an honor to hear and have so many people ask if The Tunnel was one of his projects!

I have been giving a lot of thought to bringing TToQE back next year and getting all 60 arches working properly and protecting the piece from the dangers of burning man and burners themselves. Hoping to also have time to upgrade the controls with more knob, sliders, buttons and LCD displays to aid in peoples understanding and expand the interactivity!