How to (Nearly) Waterproof a Point Source Pixel

In the spring, we’re finalizing a design which has the LEDs / drive electronics safely encapsulated in an injection-molded enclosure which will look surprisingly similar to a C9 Christmas light.

However, tooling and setup fees for the machining will be very expensive.  Plus, it takes a long time.

Here’s how I impatiently but quickly weatherproofed the pixels installed on the house.  Click any picture to enlarge.

(Note that though this seems to work well, it took a long time and was fairly boring.  Won’t be doing it again.  Also, I wanted to use regular heat-shrink tubing to seal the parts.  Unfortunately, the header pins and LED are so bendy that nothing sufficiently wide would make a good seal.)

To start, take an assembled, tested and programmed pixel.

Then, buy a roll of Heat Shrink Film from your local professional print shop.  This is the same plastic that’s wrapped around CDs and DVDs from the store.  It came in a 500 foot roll 12″ wide.  If anyone needs about 485 feet of shrink film, let me know.

Buy a Foodsaver clone from Target for about $40.  Useful because it has a strip of heating element which we use to make custom shapes with the shrink film.

Make a bag, sealed on three sides, out of shrink film.  Mine was 12″ long by 3″ wide and open on the 3″ end.

Seal the fourth side.  The plastic ‘pillow’ is now air-tight.  Test the seal by mashing it with your finger.  At this stage it’s important that the circuit be isolated from the rest of the world.

Ever so gently, press the 10 pins of the ribbon cable through the film.  If you do it right, you’ll have 10 small punctures in the plastic.  Do it wrong and the film tears and you start over.

Use a heat gun to shrink the film.  It’s soft and supple when warm – almost like cellophane wrap.  When it sets, it’s crinkly and stiff.  Funny looking up close, totally unnoticeable from a more than a few feet away.


Attach the pixel to the ribbon cable harness previously constructed.  My lights are on 8″ centers.

For even more protection, use a 1″ piece of 3/4″ diameter heatshrink tubing to lock the female and male headers together.  Somewhat like a turtleneck shirt.

Et voila.  I wouldn’t immerse them in water, but it works well to keep off blowing snow and rain.

Point Source Pixels – Fully Installed!

What a day!  This morning I drove downtown to get another 200′ of power and data cable.  I’d previously used 400′ of each for the two lower rooflines, the arch and the garden lanterns.

I finished and tested a second 8-way DMX splitter, because the upper and lower runs are assigned to separate universes.  Then, I weathersealed the remaining 100 or so pixels for the three upper runs.  

We started installing at 5:30 and were finished a few hours later.

The test pattern we ran during installation – and which is shown below – toggles between green with red sparkles, red with green sparkles and blue with white sparkles.

All told there are about 200 point source pixels and 19 ‘classic’ pixels mounted in the garden lanterns.

Click a photo once for medium size, then a second time to see in a larger size.

Will post video clips once I’ve found a 3-CCD camera that has decent dynamic range.

Point Source Pixels – Halfway Installed

Here are some pictures I grabbed halfway through the installation.  

The low parts of the house are done.  The high parts of the house are terrifyingly out of reach.  Will work on those later this week.

There are 100 point source and 19 standard pixels in the garden lanterns installed so far.  That makes 357 channels of DMX-512.

Click a photo one for medium size enlargement, then a second time to see it full size.

Point Source Pixel – First Run


[click to enlarge]


Point Source pixel. Based on the original RGB design but with a 10mm RGB LED.

I’m really happy with this design. Adding some 1″ clear heat shrink tubing will make the design waterproof and safe to use outside. Of course, it’s meant to be driven by a DMX Offset Machine, described elsewhere on this site.

The YouTube clip below is characteristsicly choppy, but in real life the colors are crisp and clear. The transitions are very smooth and the white light ‘strobe’ effect is very convincing.

To get a decent video exposure, I placed a 100W desk lamp directly above the pixel while shooting. This way, there was a reasonable balance between the LED light and the ambient light.

All current used by this device comes through the 78L05 regulator, making the system much less sensitive to voltage drops in the cable. Power supply of 7-12V DC, 70 mA per pixel, will work wonderfully.

The LED throws a neat shadow 10′ across the workshop onto the opposite wall.

Buy bare circuit boards for $3 each if you’re interested.
3/28/08 Further Experimentation 

I chained 8 of the pixels together, just to see what would happen.

Wiring is more arduous than soldering the components in place! Each pixel has two sets of terminals in parallel with each other. This makes daisy chaining relatively simple.

I used 22 gauge shielded cable with 5 conductors: DMX ground, D+, D-, Pixel Power, Pixel Ground. Wires connected to the top and bottom of the circuit board. Then, the board lays flat.

Finally, I put a piece of 3/4″ clear heat shrink tube over the entire assembly. A small hole was punched in the center to let the LED peek through.

The ends aren’t completely sealed, but adding a few small pieces of 3/8″ heat shrink would close them up nicely. Waterproofiness is very desirable.

Coming soon: Video clips & photos of the chain in action.


Bill of Materials:

  • C1   .1 uF 10v 0805 ceramic
  • C4   10 uF 25v 0805 ceramic
  • C5   1 uf 10v 0805 ceramic
  • JP1  5 pin .1″ header, or leave blank                
  • JP2  5 pin .1″ header, or leave blank                
  • LED  RGB LED, 4 pin, common cathode                   
  • PGM  5 pin .1″ programming header, optional          
  • R1   80 0805 package        
  • R2   80 0805 package    
  • R4   1000 0805 package    
  • U$1  78L05 SOT-89 package                               
  • U1   PIC 16F688 SOIC-14 package                          
  • U2   MAX485/SN75176 RS485 transceiver, SOIC-8 package
Buy bare boards for $3 in the online store.
Find a PDF copy of the schematic here.





Half a Pixel


[click to enlarge]

Half a Pixel

Half a pixel. Based on the original RGB design but with half the LEDs. 1.25″ square.

Bill of Materials:  

  • B1  5mm blue led               
  • B2  5mm blue led                        
  • B3  5mm blue led                          
  • C1  .1 uF 10v ceramic, 0805 package        
  • C4  1 uF 10v ceramic, 0805 package       
  • C5  10 uF 25v ceramic, 0805 package   
  • E1  5mm red led                            
  • E2  5mm red led                          
  • E3  5mm red led                             
  • G1  5mm green led                           
  • G2  5mm red led                             
  • G3  5mm red led                            
  • JP1  .1″ x 5 pinheader, optional    
  • JP2  .1″ x 5 pinheader, optional       
  • PGM  .1″ x 5 programming header, optional       
  • R1  1K 0805   
  • R2  1K 0805    
  • R3  1K 0805   
  • R4 1K 0805      
  • R5 300 0805       
  • R6 117 0805     
  • R7 100 0805     
  • T1  2N3904  SOT-23 
  • T2  2N3904  SOT-23   
  • T3  2N3904  SOT-23  
  • U$1 78L05 SOT-89       
  • U1  PIC 16F688 SOIC-14                        
  • U2  MAX485/SN75176 SOIC-8          
Buy bare boards for $3 in the online store.
PDF file of half pixel schematic is here.

Pixel Installations in the Field

Here’s a small (but growing) collection of projects which include our DMX pixels.

mrpackethead from New Zealand sends this photo and video clip.  Pictured are 160 of the ‘classic’ RGB Pixels, based on daisy-chaining cat5 network cable.

If you’ve used pixels in a creative or exciting way, we’d love to hear about it.  Send your pictures, links or video clips.