Bubble Display Videos

I have been playing around with the timing for how long to turn on the air pumps (as well as the delay time between bubbles). This video is my “favorite” so far for the solid bubbles (on the left) 30ms on-time, and 300ms delay. Obviously, the aquarium air stone tube (right side) needs a longer delay to separate the air pulses.

Of course, I also tried playing around with super fast bubbles!

And with the smallest bubbles I could make (the electronics can give a 1ms pulse, but the motor/air-pump needs at least 8ms of power to eject a bubble…)

Bubble Display Prototype 1

I have the physical structure, electronics, and pneumatic systems all integrated (for 2 of 6 channels) on my first prototype for the Bubble Display. The electronics are mounted on one side of the upright board, while the air pumps, check valves, LED lights and acrylic tubes are mounted on the other. (Click photos for larger versions)
The electronics for a bubble display prototype

Six air pumps, connected with check valves to the bottom of acrylic tubes filled with water

And here is a video of the system driving two channels (tubes of water). This is a 10ms bubble size, which is quite small. I will be experimenting with various lengths of time to drive the air pumps to make bubbles of different sizes, as well as experimenting to find out how small of a delay I can use without having the bubbles run into each other as they rise. (The length of the tube will affect that as well, so it’s just about time to make some six foot tubes!)

Addressable RGB LED string

This string of 20 Red-Green-Blue LED lights is addressable via SPI interface. Each LED has an WS-2801 LED driver IC and they are daisy chained in a long string. The plan is that each column in the bubble display will have it’s own LED at the base. I can even plug more strings of 20 end-to-end to expand to 40 or 60 addressable color controlled columns.

Aquarium Air Stone nozzle test

This is the 2nd test chamber I built, this time using an aquarium air stone as the air injection nozzle. The cloud of small bubbles it releases have a very different appearance when compared to the single larger bubble produced by the 1/8″ hose coupler nozzle.

I am getting more experienced using the acrylic welder to seal the bottom of the square extruded acrylic tube, but I still had some water weeping out the bottom when I tested it the first time. Adding more solvent fixed that issue.

Acrylic Column #1 (Bubble Display testing)

I finished test column #1 today. I was able to cut the extruded acrylic tube using a miter saw with no major difficulties, and pulled it across a piece of sandpaper on a glass backing to try to ensure that the end was perfectly flat. I had to use a good amount of solvent to weld the 1″ square bottom plate to the bottom of the square extruded acrylic tube. Even after my initial weld, it had some pinhole leaks that would “weep” water. I fixed them by turning the tube sideways and wiping a liberal amount of solvent along each of the four seams, allowing it to seep into the gaps (and/or melt acrylic into the gaps.)

A 1" square tube of acrylic with a bottom plate cemented to it.

As far as I can tell Continue reading

Acrylic Welding Solvent – Bubble Display Nozzle Test 1

IPS Corporation (Weld-on) acryilic welding solvent cement
This is an industrial acrylic welding solvent. Highly volatile industrial solvents have the ability to unscrew their own lids and escape into the atmosphere during shipping, so they are shipped inside a sealed metal can. It is assumed that you will have something to “cut this out” when you open the solvent and want to use it.

Can sealed by metal

I’m not going to post a picture of the warnings on the side of the can, because, well, this blog is publicly available on the Internet, possibly read by children, and man, are they scary! Cancer, infertility, death, and skin irritation. Lets just say that when you open this can, your liver pokes you in the side to remind you to put on your   nitrile   gloves.

So, what am I trying to weld together? Continue reading

A List of Bubble Displays

I’m going to be building a bubble display. So, here is my collection of related work:

  • The Information Percolator ( video ) – 32 tubes, 40mm in diameter. Overall display size 1.4m (wide) by 1.2m (tall). Approximately 25 separate “bubbles” can fit in a 1.2m tall tube. Water was used as the medium. 40mm tubes worked “better” than 20mm or 25mm tubes. Used an aquarium air-stone as the diffuser at the bottom of each tube. Each tube was also connected to all other tubes and a drain so that the water level would be equalized between them, and the water could be drained. Each tube was powered by an aquarium air pump controlled by a solid state relay. Each tube had it’s own check valve (to keep the water from flowing into the pump when turned off) and an airflow adjustment valve (to adjust for variations between different air pumps). Timing of air release is accurate to a few milliseconds, but only 25ms accuracy was needed. Note that the time a particular tube was “off” modifies how much water needs to be expelled from the system before air will flow, so sometimes 50ms is needed to produce a bubble.
  • Bubble Display (video) by Jon Bennett, Sahinaz Safari, and Gouting (Jane) Chang at the University of Waterloo is very well documented. It used glycerin as the medium and non-defused bubbles for a cleaner look and a slower scroll rate. 24 valves spaced 4.7 cm apart with baffles to keep the bubbles separated. They used a high pressure compressor with a regulator to output 12psi air at each valve. They had air pressure “accumulators” to provide a buffer so multiple valves firing at once wouldn’t reduce the pressure too much. They also had a manifold (possibly with valves to modify the air flow to each valve?) A check valve (clippard MCV-1AB) kept the glycerin from flowing back into the system. They eventually selected Parker A005-C23-2P valves that were operated for 10-20 miliseconds “on-times” (50 microsecond timing resolution was required). His suggestion was to use even smaller valves. Overall cost was large, due to the use of “full-price” pneumatic components.
  • The bubble Screen ( Video ) Bubble Screen by Beta Tank – The website was down when I accessed it, so not many details currently available.
  • Matt Bell has been working on a small bubble display and making steady progress improving it. His display uses solenoid operated valves to inject the bubbles, and his improved version uses individual tubes for each column.
  • Update: PipeDream III – I missed this one in my initial roundup, but it was mentioned in the comments of a hack-a-day post. Uses small tubing so that the bubbles don’t “catch up” to previous bubbles and solenoids to add the air.
  • Update: Bulb Bubble Display (video: video ) – I believe this bubble display was completed in 2013 (after mine) and I found it via a post to my bubble displays project video page on YouTube. It uses 64 tubes, with compressed air injection via valves controlled via shift registers. The tubes are part of a “garden partition” or tuftex type plastic wall that is already divided into cavities. I LOVE the idea of using that for the tubes, as it eliminates a lot of the tube construction / allignment issues (although I imagine you still have to seal the bottom well… They used silicon molded on the bottom of the “wall”).
  • If I missed your favorite bubble display, send me a URL linking to some useful information!

Not bubble displays, but related, waterfall displays like this one, this one, or this one are also cool, but run a lot faster, and in the opposite direction.

My thoughts:
Water for a fast rising bubble, glycerin for a slow rising bubble. Air-stones for a diffused look, or a tube for solid bubbles (which look better in glycerin)…overall the choices appear to be an aesthetic one.

Everybody who starts off with a single tank eventually goes to a series of tubes or baffles to keep the bubbles from interacting with each other (drag and drafting effects), unless they space the bubble generators out very far apart.

Carefully controlling the amount of air that is released appears to be the hardest aspect of the project. Aquarium pumps appear to have less control than solenoid operated pneumatic valves.

Common problems were leaks and difficulties sealing tank seams and mounting issues.

The biggest cost appears to be the hardware for each tube that produces the actual bubbles, with pneumatic (solenoid operated air valves) being more expensive than aquarium air pumps. I don’t plan on paying retail for my air pumps or electrically operated valves. Now, if only I could find a surplus supplier of check valves….

Most of these bubble displays were relatively short. Seeing as how you get the vertical axis “for free”, it seems like you should make your bubble display as high as your tank/tube allows. At a minimum, a six-foot height sounds like a good starting point.

Robot Pool Skimmer Propulsion Test

One of my long term projects is to build a robot pool skimmer. It will probably turn out to look even more ghetto than this pool net taped to the front of an RC boat:
Radio Controlled boat with pool net taped to the front

The point of this exercise was to test the thrust of the motors on one of the boats I purchased as a donor hull. It is able to push a normal sized leaf net around the pool (slowly).
RC boat moving in pool
Continue reading

Modifying LED christmas lights to run off of 120 volt DC

christmas lights on the front of a truck.

Normal Christmas lights will run off of a 120 volt DC source just as well as an AC source because they are a resistive load.

LED Christmas lights will also run off of a 120 volt DC power supply (such as the traction pack on my electric pickup), but because they are diodes the polarity of the supply voltage must be correct. With the string I bought, half of the string was oriented one way, and the other half of the string was oriented the opposite way. This results in each LED only being lit 1/2 of the time when powered from an AC line, but if you plug the string of LED’s into a DC source only 1/2 of the string lights up. By reversing the connections at the middle of the string I was able to get the whole string to light up.

Of course, it could be that the LED Christmas tree lights are designed to only operate at a 50% duty cycle, so I may be over-heating them, but I figure that since they are mounted on the front of my truck they should get plenty of air cooling. So far they haven’t died!