Automatic shooting range from DENDY pistol. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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Is it possible to shoot more accurately with a famous video game pistol? Of course, it is possible, the author of the proposed article answers, if it is finalized. True, now it will be evaluated not so much the accuracy of the hit as the speed of reaction to the appearance of the target. But you must admit - this is also the most important ability of a hunter!

When buying a video set-top box compatible with "DENDY", a diligent owner will definitely ask if a light gun is included in the package. The calculation is simple - no matter how long the video set-top box has served, the gun will always come in handy for children like an ordinary toy.

However, the light gun in the TV game is not only fun, but also an element of the shooting simulator. The development of the eye, the training of visual and auditory reactions, as well as the acquisition of initial skills in handling weapons are the fundamental differences between pistol games and computer fighters.

In the 70-80s, electronic shooting ranges were an indispensable attribute of the work of radio clubs. With the advent of television shooting galleries and video set-top boxes with light guns, the situation has changed. Indeed, now it is possible to flexibly change the computer and software form of targets, the trajectory and speed of their movement, and even the surrounding landscape.

Unfortunately, there are not so many game programs for the "DENDY" light gun. The most famous of them are "DUCK HUNT" ("duck hunting"), "WILD GUNMAN" ("cool shooter"), "CLAYSHOOTING" ("knock down the plate").

The main interest in shooting games is to gradually accelerate the movement of targets. With each round (stage) it becomes more and more difficult to play. Many fail to see the final part of the game.

And yet there is a way to hit the target one hundred percent, which is an interesting logical and technical problem. For a better understanding of this, it is necessary to look a little deeper at the processes taking place in the light gun.

Anyone who has ever disassembled a light gun out of curiosity could notice a small printed circuit board with radio elements inside.

All types of DENDY-gun electrical circuits fit into a simple structure (Fig. 1). A flexible four-wire cord with an X1 socket at the end connects the gun and the video console. The "LIGHT" circuit carries information about the illumination level of the VT1 photo sensor, the "GUN" circuit is the NC contact of the pistol trigger button SB1, "+ 5V" - power, "GND" - a common wire.

The signals "LIGHT" (lighting) and "GUN" (shot) are fed into the video set-top box to the inputs of logic elements. These signals are not electrically connected to each other.

A typical oscillogram of the "LIGHT" signal when pointing the gun at the target during the game is shown in fig. 2. As you can see, this signal captures pulses with the frame rate of the TV, and the pulses in the linear section are the larger in amplitude, the higher the brightness of the target on the TV screen and the closer the distance from the TV to the gun.

The informativeness of the signal lies, firstly, in the amplitude, and secondly, in the location of the pulse on the time axis.

Theoretically, it is not particularly difficult to "deceive" the video set-top box processor by supplying specially generated pulses with levels sufficient to trigger logic elements instead of "LIGHT" and "GUN".

To move from theory to practice, it is necessary to understand the general algorithm of pistol games. To this end, let's consider in more detail the logic of building one of the most exciting games for a light gun - "CLAY SHOOTING" - a two-skeet clay target shooting simulator. The plates take turns "flying out" from the bottom of the TV screen at an arbitrary moment in time, at an unpredictable angle and with a random pause between the departure of the first and second plates. The player's task is to accurately aim the pistol at the target and pull the trigger before the plate "falls" over the horizon.

First observation. If you look closely at the moment of the "shot", you will notice that immediately after pressing the trigger, the TV screen goes blank for a moment, the image of the plate is replaced by a bright white rectangle, after which the game picture is restored and the shooter sees whether he hit the target or not.

Obviously, a white target rectangle on a dark background is a high contrast test image that is guaranteed to be captured by the gun's photosensor.

Second observation. If the gun is brought close to the TV screen set to maximum brightness, then instead of improving the accuracy of the hit, the opposite effect is observed - none of the shots reaches the target. This suggests the existence of a protective zone and a special decision-making algorithm.

Third observation. The oscillogram of the "LIGHT" signal (Fig. 2), due to the inertial properties of the kinescope, does not contain components with a horizontal scanning period of the TV set of 64 μs. This means that the actions in the game pistol program must be synchronized with personnel impulses.

Based on three observations, we can imagine the algorithm of the program "CLAYSHOOTING" (Fig. 3). Initially, the program analyzes the duration of a single level of the "GUN" signal, which determines the fact that the trigger is pressed. If the duration is longer than T1, then this is not an accidental interference, not a "bounce" of mechanical contacts, but a "shot".

After the T2 time has elapsed, the TV screen becomes completely dark. The program starts to analyze the signal "LIGHT", which should be in the state of logic zero during T3.

Thus, a protective zone is formed, which increases the noise immunity of the system and does not allow hitting the target from a very close distance, since the photo sensor of the pistol can record a false alarm from a weak glow of the dark screen during T3.

At the next stage, the signal "LIGHT" is analyzed during the time T4 and, if it reaches a single level, a decision is made to hit the target exactly, and vice versa. The high brightness and contrast of the test image is shown in fig. 3 with increased amplitude and steeper signal edges.

The analysis cycle ends with the restoration of the original game picture.

Specific values ​​of T1-T4 are determined by the game program and may be different in different games. A similar algorithm can be used when writing your own light gun programs.

Experiments carried out with the supply of external signals from a single pulse generator to the "LIGHT" and "GUN" inputs of the video set-top box show that for the game program "CLAY SHOOTING" the values ​​of the algorithmic time intervals are approximately equal to CTCT2; T2=T3=T4=t, where t is 20 ms (TV frame scan period). In total, from the moment of the "shot" to the fixation of a successful hit (time T4), it can take from 80 to 100 ms.

Now the problem is reduced to the development of a device that allows you to automatically generate pulse sequences in accordance with the found algorithm.

The block diagram of such a device - a simulator of "shots" - is shown in fig. 4.

For error-free hits, the device must be synchronized from the vertical scanning signal. For this purpose, a frame pulse separator is used, the input of which receives a complete video signal output to the "VIDEO" connector of the game console.

Such synchronization helps to unambiguously fix the location of the "shot" moment within the frame.

The "shots" generator should imitate both single "shots" and firing "bursts" with an adjustable rate of fire.

The actual binding of the moment of "shot" to the beginning of the next frame is carried out by a synchronizer, from the output of which the "GUN" signal goes directly to the video set-top box, and the "LIGHT" signal goes through the delayed pulse shaper.

The electrical circuit of the simulator is shown in fig. 5. The video signal of the set-top box, taken from the X1 "VIDEO" connector, is fed through the C1R5C2R1R2R3 filter to the input of the DD2.1 single vibrator. The single vibrator performs a dual function: it serves as a threshold element for the sync input C and normalizes the received frame pulses by duration (6...7 ms). The trimming resistor R2 sets the optimal response threshold, the estimated voltage on its engine is 2,0 ... 2,4 V. Diode VD1 accelerates the discharge of capacitor C4.

"shots" with an adjustable frequency of 0,5 ... 2 Hz are assembled according to the standard scheme on the elements DD1.1 - DD1.4. Single "shots" are formed by the button SB1 and resistor R8. Switching modes "Single" - "Multiple" switches SA1.

The synchronizer is made on the basis of the D - trigger DD2.2. The signal generated at its inverse output is fed through the buffer element DD1.6 to the "GUN" (X2) input of the video set-top box.

The signal from the direct output of the trigger DD2.2 starts the shaper of the delayed single pulse on two single vibrators DD3.1, DD3.2. The delay is adjusted by the trimmer resistor R9. The pulse duration is fixed at 6...7 ms and, if necessary, can be changed by resistor R10. Diodes VD2, VD3 serve to accelerate the discharge of capacitors C5, C6.

The DD1.5 inverter, as an element with increased load capacity, is a buffer for feeding the "LIGHT" (X2) signal to the video set-top box.

In the device, you can use fixed resistors with a power of 0,125 W or 0,25 W, tuning resistors SDR - 19a, capacitors K10 - 17, KM - 56. Diodes - any other low-power silicon, for example, KD509A, KD521A.

Switch SA1 - small-sized sliding PD9 - 2, PD53 - 1, in its absence, you can use hinged jumpers. The KM - 1 button is used as SB1, although it is permissible to use the electrical contacts of the light gun trigger.

The parts are placed on a printed circuit board (Fig. 6) made of one-sided foil material. The design must provide free access to trimming resistors. It is possible to use variable resistors connected by conductors to the corresponding pads of the printed circuit board.

Connector X1 is a tulip plug used in cables for connecting VCRs to TVs at low frequency.

Connector X2 - a 15-pin socket from the light gun cord, a view of it from the front side is shown in fig. 7.

If the design is assembled as a temporary one, then the wires of the X2 connector can be soldered directly onto the printed tracks of the joystick board inside the video set-top box.

The automatic shooting range is connected to the video set-top box "as shown in Fig. 8. The joystick is connected to the main game connector "CONTROL 1", the simulator - to the auxiliary "CONTROL 2", where the light gun was previously connected.

When the video set-top box is turned on, power is supplied through the X2 connector to the "shots" simulator, the device is ready for operation. Initially, the resistor R7 should be adjusted at pin 4 of the DD1.4 element, the pulse repetition period, equal to approximately 0,9 ... 1,5 s. Next, you need to make sure that at pin 12 of the trigger DD2.1 there are stable non-bifurcated pulses of negative polarity with a period of 20 ms and a duration of 6 ... 7 ms, otherwise you will have to set these parameters with resistor R2. The duration of the pulses at the output 2 of the single vibrator DD3.1 is set by the resistor R9 in the range of 80 ... 100 ms.

Now about the procedure for working with the simulator. All that is required from the player is to insert the cartridge with the program, turn on the power of the video set-top box, select the game "CLAY SHOOTING" with the joystick and press the "START" button on the joystick.

When the simulator is set to single shooting mode (SA1 "Single"), any press on the SB1 button with a target on the TV screen instantly leads to an error-free hit. The main thing is not to be late so that the target does not disappear beyond the horizon.

If the SA1 switch on the simulator is in the "Repeated" position, then on the TV screen you can watch a "cartoon" in which the shooter always wins by spending two or three cartridges. If this does not happen, it is necessary to choose the optimal position of the sliders of the resistors R2, R7, R9 right during the game.

After about 20 minutes of continuous automatic shooting, you can find out what surprise the authors of the program prepared for the player who scored the maximum possible number of points, and after a while the total number of game rounds will become known.

Author: S.Ryumik, Chernihiv, Ukraine

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