Hardware Update – April 16th, 2012
Wow – been a long long time since my last post – sorry about that!
Since then the 2011 show has come and gone (it went great!) and I’m well into getting ready for the 2012 show. By far the largest change will be the new MegaTree. It will contain 32 strings of 42 pixels (1344 pixels or 4032 channels) using the TLS3001 chips. What does all that mean? I used a pixel strip for the show last year – basically, it’s a flat strip with small (5mm x 5mm) RGB (Red/Green/Blue) LEDs spaced at 30 per 1M of strip. Each RGB LED is addressable which means I have direct control of each LED and each color. These new strings I will be using for the tree are similar except they look much like common Christmas light strings instead of a flat strip. This will present a “canvas” on which to apply different effects, text and animations onto. They will be driven with the SanDevices E681 controllers (two of them) which I just completed building. By using 16 strings of 42 pixels per controller, I can maximize the pixel count. The controllers support 680 pixels and 16 x 42 is 672 pixels – close enough! The tree will be 18-20′ tall or about twice as tall as last years. The TLS3001 chip on these pixels are a bit special as well – they support 12-bits or 4032 levels of dimming over the more common 8-bit or 256 levels. While the data being sent to them from the PC will still be 8-bit, the controller can shift the levels around so there are more steps at the lower levels and more at the higher levels (known as gamma correction). This will allow very smooth fades/ramps of the LEDs. I still need to build the framework to hold the tree strings however.
I also purchased some GE Color Effects pixels on eBay pretty cheap. These have 32 levels of dimming so they don’t ramp/fade nearly as smooth as other pixels – but they’re fairly large so I’m planning to put these on roof ridgeline somehow. They should show up pretty well. Another E681 will control those and I will still have the window strip display from last year as well. It should make for a very colorful setup!
I also got some cheap 4 watt LEDs – some in enclosures and some loose. The ones in the enclosures are very bright and I plan to put the others in PVC tubes to keep them dry. They will be pointed directly at the cars and be used as bright “blinder” lights. I’ll have about a dozen of these spread over the roof. These draw a fairly hefty amount of power so my good ‘ol Ren48LSD boards can’t be used for this directly. I have a few leftover DCSSRs as my plan A. My “plan B” consists of a new board I am working on called the DIYC RGB6. Basically it is a new 18-channel controller (DMX only) with six RGB outputs. It uses the same high power output circuit as the DCSSRs but uses an 18F2525 PIC to drive the outputs. I’m still working on the code for this but my hope is to combine the DMX code from the Microchip site (AN1076) and add the MIBAM dimming code to it. MIBAM is a variation of “BAM” or Bit-Angle Modulation dimming that provides smoother and less CPU-intensive dimming over standard PWM code. The MIBAM (MIrrored BAM) variation gets rid of an issue where there’s a slight glitch when crossing the 127/128 dimming levels. The original code is written with a combination of PICBasic and PIC assembly while the DMX code is pure assembly. I’m trying to determine how to mix the two together but my coding skills are poor at best…
Anyway – that’s where things are – talk to you later!































