Installation of laser effects. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Color and music settings

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Many have seen devices for sale that draw various geometric shapes similar to Lissajous figures on a wall or other suitable screen with a laser beam. One of the most common devices of this kind is called Laser View. This is a microprocessor-controlled device, switching modes in it is carried out using two buttons. Beautiful, comfortable, but the price is about $70 (no comments). It is not surprising, therefore, that many radio amateurs make such devices on their own.

The most famous are two types of home-made laser effects installations: NK300 ("Laser Effect") - a device manufactured by Master Kit as a kit for self-assembly, and "Concert Laser" - a device described in the book by Herve Cadino (Herve Cadino) "Color and Music Settings" (translated from French, M: DMK, 2000).

The Master Kit device is made on the basis of a specialized microcircuit, to which two collector electric motors with mirrors mounted on shafts are connected. The rotational speed of each electric motor is regulated separately by its variable resistor. At different ratios of the rotational speeds of electric motors, various geometric shapes are obtained on the screen. Despite the design, which is very convenient for assembly (electric motors and the laser are attached directly to the device board with clamps), as well as the very reasonable price of the kit (12,44 USD without laser), the device has a serious drawback: it uses collector electric motors that have a low reliability.

Hervé Cadino's "concert laser" is a more complex device, there are as many as nine operational amplifiers in it! It has a very interesting function - synchronization of lighting effects with music using the built-in microphone (there is a similar function in Laser View). The book also contains a very high-quality drawing of a printed circuit board. Well, it’s quite good, if, of course, there is ferric chloride, a photoresist. Nothing is said about the type of engines in the book, but judging by the presence of protective diodes, they are also collector ones.

When I also wanted to assemble a laser effects setup for myself, I decided to do everything in a completely different way. First, no collector motors! Moreover, there is an inexpensive alternative - these are miniature DC fans used in modern PCs. These fans use non-contact electric motors with Hall sensors. If in a collector DC motor the windings are located on the rotor, and the magnets are on the stator, then in a non-contact one it is the other way around: the rotor is a permanent multipole magnet (as in an AC synchronous motor), and the windings are on the stator. Hall sensors track the position of the rotor, giving signals to a specialized microcircuit, and it, in turn, switches the windings. Such fans also have another advantage: you don't have to think about how to fix the mirror on the shaft, you can simply glue it to the impeller! Non-contact motors have almost the same linear dependence of speed on supply voltage as that of collector motors. Secondly, why fence such a complex scheme, you can adjust the speed with the help of the good old adjustable rolls! Here, look what I got here:

As an EL1 laser, an ordinary laser pointer with a power of 1 mW, bought at a newsstand for 55 rubles, is used. Since, according to information from the Sam's Laser FAQ website, laser pointers are afraid of microsecond surges in the supply voltage that can occur in compensating stabilizers at the time of power-up, firstly, high-capacity capacitors are used for protection, and secondly, a soft start device on incandescent lamp HL1. The lamp HL1 and the resistor R1 form a voltage divider, and at the moment the power is turned on, the resistance of the lamp filament, and hence the voltage drop, is small, and as it warms up, it increases to about 3 V. This is less than the nominal supply voltage of the lamp (6 V), and a laser pointer (4,5 V), which also has a positive effect on their service life. Of course, the laser pointer power button should be fixed in the pressed position with something like electrical tape. When connecting a laser pointer, do not forget that it is afraid of static (that's why they are made in metal cases), and in addition, its body is connected to the plus, and the spring to the minus.

Attention!!! Do not allow laser radiation to enter your eyes - it is dangerous!!! A working installation of laser effects should be located so that the beam under no circumstances could get into anyone's eyes, as well as outside the room (for example, through a window). It is also not allowed to use the installation of laser effects (as well as other light-dynamic installations, including strobe lights, flashing garlands, color music) in the presence of people suffering from epilepsy.

It is recommended to use the cheapest laser pointer with a 1mW output power in the device, but even in this case, the safety regulations should be strictly observed. Experimenting with more powerful (and more expensive) laser pointers, such as those with an output power of 3 mW or more, and helium-neon lasers, is only recommended if you have a lot of experience with such devices. In any case, it is highly recommended that you read the Laser Safety document on Sam's Laser FAQ site, as well as the laser safety literature available in your home or local library.

Electric motor speed controllers are assembled on LM317T microcircuits in standard inclusion. The color coding of the power wires for all fans is the same: red - plus, black - minus. Some fans also have a white wire - this is a tachometer sensor. Here it is not needed, you can even unsolder it from the fan board so that it does not interfere. It is desirable that both fans are the same.

Mirrors from Chinese round sharpeners are ideal as mirrors, but since they were recently discontinued, I had to use an alternative option - cut mirrors from a damaged CD. The option, I must say right away, is not ideal, since the brightness of the beam turns out to be less: firstly, the CD acts like a diffraction grating, and part of the light is scattered in the wrong direction, and secondly, the CD is not so good reflects light. But it works! Mirrors are glued to the fan impellers with hot glue, and since it is impossible to glue the mirror perfectly parallel to the impeller, each mirror will create an elliptical sweep during rotation. Figures similar to Lissajous figures are obtained by superimposing two elliptical sweeps on top of each other.

The laser pointer and fans are placed on the Plexiglas plate as shown in the figure:

First you need to glue the fans with the same hot glue, and then proceed to determine the place where the pointer will be located. With the fans stopped, the pointer must be positioned so that three conditions are met: the optical axis of the pointer must be at the same height as the centers of the mirrors; its beam fell into the center of the first mirror, and the beam reflected from the center of the first mirror fell into the center of the second mirror. It is very simple to do this if you remember the rule known from school: the angle of incidence is equal to the angle of reflection. When everything is set up, you need to glue a piece of plastic to the plexiglass in the right place with a height equal to the height of the centers of the mirrors (minus the radius of the pointer), and a pointer to it, placing it as indicated above. While the hot melt is cooling, you can finally configure everything.

Now try twisting the variable resistors. If everything is done correctly, you will see various geometric shapes on the wall. Since we have elliptical sweeps, the figures will not be the same as the Lissajous figures on the oscilloscope - they will be even more beautiful! In other devices of this kind (including Laser View), the scans are also elliptical. The knobs should be rotated slowly, since the impellers of the fans are a kind of flywheels, and the speed will not change immediately after turning the knob, but after two seconds. Otherwise, the principle here is the same as with the oscilloscope: each figure has its own frequency ratio, if the ratio is accurate, the figure is motionless, if it is inaccurate, it rotates at a certain speed in one direction or another.

Now let's think together how we can improve this installation of laser effects. The first thing that suggests itself is to add a broken line function, similar to the one in Laser View. Just do not try to modulate the laser beam by switching the power supply - the laser will not last long. In extreme cases (this is also advice from the Sam's Laser FAQ site) - you can try and switch, but you don't need to completely extinguish the laser, but turn it on at half or at full power - it's more reliable. The frequency is selected experimentally. A much more civilized way is to pass a laser beam through the impeller of another fan, so that the impeller, while rotating, acts as an obturator. I tried this method and got good results.

Another interesting effect implemented not only in Laser View, but also in Herve Cadino's "Concert Laser" is musical control. Think for yourself how it can be implemented here.

And here is another effect that is not even in Laser View. We have here, therefore, two elliptical sweeps - you can also add a third. You will need one more fan with a mirror and another power regulator, similar to the existing ones - then the device is configured in the same way as a two-fan, well, a little more complicated. I have not tried this yet, but I think it will be good.

Well, okay, you say, but what if you make a device that draws on the wall with a laser beam not abstract figures, but different letters, numbers, pictures? It will be cooler than propeller clocks! Well, this is possible. On the same Sam's Laser FAQ site, it was said that the laser beam can be deflected using piezoelectric sound emitters. Of course, not all piezo emitters are suitable, but only those in which the membrane is cleaned to a mirror shine (mostly imported piezo emitters meet this requirement). According to the site Sam's Laser FAQ, these devices noticeably deflect the laser beam at a voltage of 50 millivolts on the piezocrystal, and at several volts they generally deflect no worse than fans. Well, if this is true (honestly, I didn’t check), then you can take a PC with two LPT ports (I wonder how you can put two multicards in one PC so that one parallel port is LPT1 and the second is LPT2?), on hang each port on a kovoks (this, if you don’t remember, is such a DAC on resistors in the form of an R-2R matrix), connect a piezo emitter to each kovoks, so that one deflects the beam horizontally, and the other vertically. What this thing will draw depends only on the skill of the programmer. Too bad I don't know assembler. You can do without a PC - just connect one of the well-known devices such as "Numbers on the oscilloscope screen" to the piezo emitters. Here is a virtual wall clock for you. And there is one circuit to add a diagonal axis to any oscilloscope - with its help you can get much more beautiful figures. But here you can do without it by adding a third piezo emitter that deflects the beam diagonally. Of course, this hypothetical device is not suitable for use as a conventional oscilloscope - of course, if you are not satisfied with an oscilloscope that works only with audio frequencies :-). And for applications like "Jean Michel Jarre to myself" - just right.

And to get to the Sam's Laser FAQ site, you first need to go to the repairfaq.org site, and then select Sam's Laser FAQ. First, of course, read the Laser Safety document, and then look at Laser Experiments and Projects - this document is still "under construction" and develops very slowly, but it already has room for things like Laser Clock or Laser Oscilloscope - which Well, let's hope that they will be posted there soon.

Good luck!

Author: Num Lock; Publication: N. Bolshakov, rf.atnn.ru

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