WS2801 RGB String Driver

[PKimbell]

Ok, I'm new to the controlled/animated light displays, but I do have a background in electronics.  I have been researching the hardware (controllers and lights) I will be using for a 2012 Christmas display.  I am planning on using DMX E1.31 controllers for RGB Pixel Strings I plan on installing on the eves, gutters, and around the windows of my home.  I'm also planning a Mega tree using the same RGB Pixel Strings.

Now my question....
I did not think I needed RGB Pixel Strings (i.e. WS2801 controlled LED strings) for items such as bushes or smaller Christmas trees.

Example Link to a RGB Pixel String:
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I decided the bushes and small Christmas trees would always be solid colors and a RGB string was fine for each bush or small tree

Example of RGB String:
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I understand the concept with RGB strings and driving each channel (R,G,B).  What I am finding very interesting is the lack of a simple controller to control these in-line or like a string of RGB Pixel Lights.

If a WS2801 (just as an example) is installed in each RGB Pixel of a string, why could you not use a WS2801 and have it drive 3 NPN transistors from each of it's 3 LED outputs....one transistor for each channel of the RGB String.  Theoretically, if you had a nest of bushes together, or a collection of small trees together (each with their own RGB String), you could address each object as if it was a single pixel of an RGB Pixel String. 

It seems a WS2801, three NPN transistors and a few resistors would be all you would need.  Actually at the top of page 10 of the WS2801 datasheet ( You are not allowed to view links. Register or Login ), it shows the exact idea I am thinking of for each of the RGB channels. 

Does a device like this exist yet? 

[RJ]

Yes,
 it has not been released yet. you do not want a chip to drive it or you need an SSC to then control that so you make an SSC that does it all on its own, But we do not use the 2801 chips in smart strings.

One reason there has been little rush is that it does not save much money and then you are limited to string control. If you go with the normal setup you can control the string or each light depending on what you want.


RJ

[rm357]

If I understand correctly, you want to use the dumb string to save money where you don't need node-level control. However, you don't save as much as you would think. Shipping from china adds another 50% to the total cost, so rather than the dumb string costing 1/2 as much per pixel, it's more like a 30% savings. Granted, that still adds up, but you have locked yourself in to whole string mode.

Also, be wary of the IP67. It may not matter as much with the dumb nodes, but on the smart ones we've had a lot of issues. You need the IP68 if you plan to leave these out in the weather.

Also, the smart strings we use are the 12v 180x style chips. To use the smart string controllers that are available through this site, you really should buy nodes using the links in the wiki. All 180x chips are not the same - there are 5, 12, and 24 volt versions and there are slow, fast, and very fast configurations. If you don't buy through the wiki, you risk getting an incompatiple configuration.

RM

[PKimbell]

Thanks for the replies.  RM, you are right in my thinking.  I think I may have thrown others in my definition of terms.  The savings I am thinking do come from the cheaper "dumb string", but mainly in the cost savings and the simplicity of the controller.  But don't forget about the fewer rows in the control software to manage.  My subject does mention the WS2801, but it could be any RGB driver chip. 

Thanks for the information about the weather kindness (IP68 vs IP67) of the strings I provided as examples....I will keep an eye on these when I place my order.  In the past, before stepping into the Lighting control Arena, the lights I would install on the eves and gutters were mounted to lengths of PVC pipe cut specifically to those areas of the house.  'L' hooks were permanently installed into the fascia of the house to allow the PVC to hang from them.  Lights were simply zip tied to the sections of the PVC pipe and hung with a modified painter’s pole.  In later years, the step to ease the install of the lights/PVC sections, I ran aircraft cable through the fascia into the attic.  Lower the cables, attach the cable to the PVC and pull the cables back up and the lights were hung.  The all-day task of hanging lights with a ladder was reduced to 30 minutes.  If a section had a bulb out, I simply lower the section via the cables; fixed it and pulled it back up.  No ladder work anymore.  This also allowed changing the lights much easier as I could plan and attach the strings before they ever touched the house (and I could do it in my warm garage; not in the weather). 

For the RGB lights, I hope I can do a modified version of this and mount the LEDs inside the PVC pipe and have them stick out though holes drilled at fixed intervals.  The previously used install process would still work the same.   The only downside to this is I am in a new house this year and I have to perform these steps all over again.  The good side of things is I know exactly how to do it this time.

This PVC process would not work for the bushes of course and I will look out for the IP68 version of the LEDs.