Laser range. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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The so-called laser (light) pointer has now become a popular childish entertainment. Produced as a miniature working tool for teachers, lecturers and guides, it attracts daring fans of science fiction with the opportunity to play the "engineer Garin's hyperboloid", highlighting one or another detail of an object of interest at a considerable distance with a highly directed light beam. Fortunately, such games do without negative consequences, because in these pointers it is allowed to use only semiconductor lasers or LEDs (the option most often used by manufacturers) with built-in optics, the radiation power of which should not exceed 1 mW. An increase in the concentration of light energy in an extremely small solid angle can create, according to experts, a certain danger to vision - when the beam enters the eye directly or after reflection from a mirror surface.

Owners of laser pointers can be adapted for an interesting and completely safe fun - a home photo shooting gallery. The light pulse will serve as an analogue of a bullet, and the target photo sensor will become the receiver. In case of hitting the target, an electrical signal will appear, which will cause a light (completely harmless) response - confirmation of a well-aimed "shot".

Minimal modification, in which the laser pointer turns into a "light weapon" for the photo shooting range

Schematic diagram of the phototarget

The weapon of the photo shooting range is a laser (light) pointer, supplemented by a simple electrical switching device and built into a ready-made or home-made model of a pistol, carbine, etc. When such a weapon is removed from the fuse (contacts SA1 are closed) and the trigger guard is not pressed (button SB1 is open), then the electricity, coming from the battery GB1 through the current-limiting resistor R1, will maximally charge the high-capacity capacitor C1. When a photoshot is fired (pressing SB1), a quick discharge of C1 will switch to the laser pointer A1. The latter will give out a short pulse of directional light, which, when it hits the photo sensor, will cause a response of the target (flash of the LED - indicator of hitting the target).

The glow of a laser pointer in a home-made photo shooting gallery - in decreasing intensity, in the range of discharge voltages on C1 from 4,5 to 3 V. After releasing the SB1 button, the "self-charging" of the high-capacity capacitor will begin, and after about three seconds the light weapon is again ready to hit the target, where a phototransistor VT1 is used as a light-receiving element. From the usual bipolar semiconductor triode, the latter is distinguished by a fundamentally different control of the collector current, when the result is achieved not by changing the electrical bias to the base, but by illuminating it from an external source, for which a translucent window is provided in the case protecting the crystal.

In the initial state, when the BA1 toggle switch has already applied the supply voltage to the photo target, and the phototransistor has not yet been lit and locked, the so-called high logic level (log. 1) is supplied from the VT1 collector to the input 1 of the 001.1 microcircuit cell of type 2I-NЄ, which together with 001.2, capacitor C1 and resistor P!3 signal converter. Inputs 5 and 6 001.2 are “grounded” through the YZ, and log.1 is transmitted from output 4 of this cell to input 2 001.1, which is why a low-level signal (log.3) is “on duty” at output 001.1 0, as well as at inputs 8, 9 and 12, 13 threshold level 001.3, 001.4. Obeying the logic of this device, on the paired outputs 10, 11 of the 001 microcircuit there will be a high level signal, which is connected to the base of the transistor VT2 (power amplifier operating in the key mode) and locks it.

With a well-aimed "shot", the light pulse enters the window of the sensitive VT1. The phototransistor turns on. As a result, the voltage at its collector (and, therefore, at input 1 of microcircuit 001) will drop to log.0. Cell 001.1 will switch to another steady state and its output will go high. This signal will be instantly transmitted through an uncharged capacitor C1 to inputs 5, 6 of cell 001.2, which will immediately switch and from output 4 will give log.0 to input 2 D01.1. Log.3 will remain at output 1, despite the termination of the light pulse and the restoration of a low level at input 1. The state of cells DD1.1 and DD1.2 will be maintained until the capacitor is charged. All this time, cells DD1.3, DD1.4 also remain in the switched state, and log.0 at their outputs allows you to keep the transistor VT2 open, creating conditions for a response signal about hitting the target - the glow of the semiconductor indicator HL1.

When the capacitor C1 is charged, the current passing through it and the resistor R3 will stop. The voltage at inputs 5, 6 DD1.2 will drop, and the entire device will return to its original state. That is, the duration of the response signal about hitting the target (glow of the semiconductor indicator HL1) is determined by the values ​​​​of C1, R3 and, subject to the values ​​\u2b\uXNUMXbspecified on the circuit diagram of the photo target, is approximately XNUMX s.

The main purpose of the HL2 LED is to signal that the target is connected to a power source. With the placement of this indicator (and, of course, the phototransistor itself) in the center of the "bull's eye", it will be possible to train and hold competitions for shooting accuracy in a photo shooting gallery, but according to more strict and complex rules. For example, in a dimly lit room or even in complete darkness, using the green "sparkle" of the HL1 LED as target designation. The red "light" of the more powerful HL1 (hit indicator) can be placed at the edge of the target.

The "electronics" of the target, with the exception of the phototransistor, LEDs, and the power switch, are mounted on a pseudo-printed cut-out board made of one-sided foil plastic.

Pseudo-printed slotted circuit board and photo targets made of foil plastic

In the design of a home-made photo shooting range using a laser pointer as the basis of a "weapon", the familiar and well-proven fixed resistors MLT-0,25 and the "variable" SP-0,4 or their analogues, the KM 1-1 microbutton, and the K50-capacitors are quite acceptable. 6 and K50-38, micro toggle switches MT1-1. The photo target is powered by a compact 9-volt "Krona" (if the intensity of training is relatively low; otherwise, a more powerful source is indispensable, which can, for example, be made up of two series-connected 3R12 batteries). Three AAA (LR03) galvanic cells connected in series can guarantee proper power supply for the "laser weapon".

The process of debugging a self-made photo shooting gallery takes a minimum of time and comes down only to setting the required sensitivity level of the light-receiving cascade with a variable resistor R1 and matching the aiming device with the beam in relation to the distance of the photo target. Power to the pointer during this coordination is supplied directly from the GB1 battery with the SA1 switch.

Author: Yu.Prokoptsev

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