"Can you make an interactive variable colour bubble tube -
two foot wide and ten foot tall?"
I am not very good at saying "no" to challenges like this - especially when it's a client that asks. As with most challenges, my first step is to make a prototype.
Here's a video of the prototype in action, plus some explanation of what went into it:.
The rest of this blog shows some of the making involved.
I used 50mm External Diameter, 44mm Internal Diameter 2000mm long clear acrylic extruded tubes (from The Plastic Shop about £17+VAT each) a RGB (Red, Green Blue) Luxeon Rebel LED board* and an aquarium pump. I had a bung made to connect the pump to the tubes, and added a one way valve, bought from a pet shop.
*(If you want to get your own board made the Eagle Files are available here - just replace the white LED's with LXML-PD01-0040 LXML-PM01-0080 and LXML-PR01-0500)
The outside of the bung was polished with Autosol metal polish to make it clear. To focus the light up the tube, I used a lens (part number PL350A06NK)
The photo of the bung shows the lens attached to the bung with red sugru. The feet of the lens pass through the PCB, so it takes the weight of the tube plus water and the LED's aren't crushed.
To make it interactive I used an arduino and some prototype PCBs that transfer data from sensors to an arduino and from the arduino to outputs, using controller area network (CAN bus). These PCB's are part of a distributed IO system called "Touchbridge".
For the inputs I used vandal-proof (it's aimed to be used by kids!) LED backed buttons to control the lights and turn them all off, and a switch to turn the pump off.
The LED’s consume a lot of power - more than a typical LED (350mA to 700mA per LED - compared to 10-20mA of a typical LED). A microcontroller such as an Arduino cannot output this amount without amplification - the Touchbridge PCB's allowed for this too. The LED's needed some rather large resistors (the gold things in the photo below) - the metal channel they are in acts as a heat sink.
Next I wanted to make some form of stand for the tubes - so I made a test-tube rack using a couple of planks and some staircase spindles ...
I made and painted the rack. The indents in the bottom were needed to stop the tubes slipping sideways. The extra two bits of wood that I painted were stabilising feet.
I only needed to make one prototype for the bubble tube - but I had bought four tubes. I like to make my prototypes useful in other areas, so I decided to make a game with them. My whole prototype could then be taken to Makerfaires or even the village fete.
As I had a supply of ping pong balls left over from making glowing eyes (blog here), and they fitted in the tube, I decided to use an ultra sonic range measuring sensor to control a 12V centrifugal blower (fan). I could then balance a ping pong ball up the tube at different heights. I had to put some tape across the top of the tubes to stop the ball flying out. With two sets, the competition is to keep it in the middle - without hitting the top or bottom.
The final tube I put some Christmas Lights in - controlled by a relay. A relay also controlled the aquarium pump I used for the bubbles.
Using a relay separates the mains power from the Arduino microcontroller. I made some boxes for the relays - these and the cable glands are waterproof, as I want to be able to make an outside installation with them all later.
The whole system works and I am very pleased with it. I've even tried it out with real live people (at Makerfaire UK in 2013) The two foot diameter ones will need a much bigger pump, but the principles will be the same.
Below are a couple of shots of Mark the cameraman and I filming the video. The photo on the right is filming my finger pointing at things.
Can you see a use for things like this? How would you adapt it? What would you use it for? Add a comment below - I'd love to hear your ideas.
Update 28th Sept 2015: Someone asked about the enclosures and connectors:
The enclosures were these: http://grh.premierfarnell.com/pageredir.aspx?c=EU1&u=jsp/search/productListing.jsp?CMP=SOM-YT-LRo-TestTube%26SKUS=1217485
The connectors are Bulgin mini buccaneer series http://grh.premierfarnell.com/pageredir.aspx?c=EU1&u=jsp/search/productListing.jsp?CMP=SOM-YT-LRo-TestTube%26SKUS=225770)
There's also some "normal" cable glands http://grh.premierfarnell.com/pageredir.aspx?c=EU1&u=jsp/search/productListing.jsp?CMP=SOM-YT-LRo-TestTube%26SKUS=1621070
If using any of these, make sure you get all the bits - lock nuts, inserts etc. Also, you can get base plates for the enclosures which makes life easier.