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Arduino Bubble Display


Hello everyone!

This time I post the continuation of experiments with an air bubble display.
Those who have not seen the first part can go through and watch the video here .

As a result of the first experiment, it turned out that with the smallest possible size of the bubbles, the distance between them should be at least 4-5 cm. Otherwise, in the liquid, between the bubbles there is a mutual influence on each other, both in the horizontal and in the vertical plane.

To fix one of these problems, I ordered acrylic partitions made by laser cutting.

In the first part, many advised me to use glass or plastic tubes, but I still chose acrylic partitions. Because when calculating the costs, it turned out that their cost is cheaper and it is easier to assemble a finished structure from them. Which also played a role in this choice.

I was very pleased with the result, since now you can move on and assemble a large, full-fledged bubble panel. On which it will be possible to display large images.

Now I’ll tell you everything in more detail.

Screen assembly


Details for partitions, I drew in the simplest online editor tinkercad. The editor has such an intuitive interface that it took no more than 5 minutes to create the parts I needed.



The painted parts were cut out to me by an old friend, on a laser cutting machine.
In the photo they are still covered with a protective film.



Assembling the bubble screen itself took quite a bit of time. And reminded me of the assembly of the children's designer.

I did not stick the partitions themselves, since they are well sandwiched between the upper and lower covers.

In the photo below, the background screen is complete.



Scheme


The scheme is simple, I did not have to pickle and solder any boards. Since I used the finished components and connected them with dupont wires.

An encoder can be excluded from the circuit, but then it will be necessary to select the size of the bubbles and the distance between them by the method of repeated flashing of the controller. Which is not very convenient.

As the keys for the electrovalves, I used the driver board from the 28byj-48 stepper motor. The ULN2003 chip on the board is mounted on the socket and in case it fails if the output is accidentally shorted or when the power is reversed, it can be easily replaced. ULN2003 is capable of withstanding currents up to 500 mA on each of the seven available channels. Protective diodes that protect the transistor switches from EMF self-induction are already integrated into the chip. Which eliminates the need to solder them to each electromagnet.

Valve response times are poor. A weak spring will not allow the valve to close quickly. And an electromagnet cannot cope with a powerful spring. Therefore, in the video you can see the minimum possible size of the bubbles. To get such a result, I had to increase the voltage on the valves to 10 V and reduce their response time.



Circuit components


The circuit consists of the following radio components:

  • Arduino nano
  • Encoder
  • 28BYJ-48 stepper motor driver
  • Connecting wires
  • The cheapest electromagnets bought in China

Sketch for Arduino


The code for Arduino can be downloaded here .

The font is not completely drawn, only numbers, Russian and English capital letters.
The encoder can adjust the size of the bubbles and the distance between them. Rotation without pressing adjusts the size, and rotation with pressing adjusts the distance.

The variables in the code that you should pay attention to:

uint16_t bub_size = 4500; // this is the size of the bubble
uint16_t bub_space = 900; // this is the distance between the bubbles
uint16_t step_bub_size = 300, step_bub_space = 10; // this is the step of building up the above variables with an encoder.

Conclusion


In conclusion, I would like to add that good results can be achieved on large sizes of the bubble panel. Since with increasing distance between the air bubbles, their mutual influence on each other can be completely eliminated.

Creeping line speed can be achieved in several ways. You can increase the size of the bubbles or reduce the viscosity of the liquid. As a liquid, you can use water, oil, shampoo, liquid soap, glycerin.

When using water or vegetable oil, the bubbles will not have beautiful, even ball shapes.

I hope my experience was useful.

If you still have questions, then ask. I will be happy to answer them.

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