Recently many enthusiastically made Amateur filming. And today they translate accumulated in the personal archive of films on modern media such as magnetic tape or CDs. It is easy to do even in Amateur conditions. Enough video camera to film a movie, projected on the screen. Given the low resolution eight-millimeter film, VHS lacking in abundance. However, for a reshoot need to take care of synchronization of operation of the projector and the camera...
The speed of projection of the film must be such that the frequency of the flicker image equal to the field frequency of the television signals is 50 Hz.
Violation of this condition will affect the video quality. When viewing it on the TV will be observed periodic changes in the brightness of the image.
Widespread projectors "Luch-2", "Wave", "Rus standard for eight millimeter movies the frame rate of 16.7 s-1) provide the desired frequency of stranded smooth. Unfortunately, if you do not take special measures, projection frame "floats" under the influence of warm-up of the mechanism that changes the voltage in the network and other difficult-to-count factors. You can, of course, just to maintain manually controller of the projector, constantly watching stroboscopic marks on the grip frame. This technique is suitable if you have promptly to reshoot a couple of five-minute films. But when the volume of the archive - a few hours projection, without automation is not enough.
Perfectly cope with the task, for example, stabilizers velocity of projection, described in [1, 2]. However, the feasibility to collect the device from over a dozen chips to perform, in General, a single job is questionable. Between still in 1969, he published an article [3], which proposed more easy solution. It was, of course, not a rewrite of the movie on video, and about synchronize the projector with a tape recorder for recording and playback of sound support.
Mounted on the shaft of the gripper mechanism of the projector Cam during demonstrations of each frame three times closed circuit is included in the power lead the projector electric motor, the contacts of the Electromechanical switch, the employee kind of phase detector. As a result, the equality of frequency shorting the mains frequency (50 Hz) was controlled automatically.
A similar device was made by the author and have been successfully used in for a number of years. Practice has shown lack of reliability of the contact sensor, and place it in the projector was not easy. Better to use a proximity sensor. This was also described in [3], but its performance on element base of those years has caused serious doubts. Was manufactured and tested in work a simple synchronizer, operating on the above principle, but with proximity sensor on modern elements. Make and develop it by in a single day.
The synchronizer circuit shown in the figure. There are also few people the extant scheme of cinema "Luch-2" (circled dash-dotted line, positional notation elements match factory), with whom works synchronizer.
The sensor projection is the optocoupler from the emitting diode IR range and VI photodiode BL1. Optical coupling between them three times during the demonstration one frame is interrupted by the shutter of the projector. Emitting diode V is connected via the rectifier (diode bridge VD1) to the secondary winding of the transformer TR1 projector. Diode current, limited by resistor R2 should not exceed 100 mA.
Direct voltage drop (approximately 1.5 V) led green HL2 glow is not enough to open the composite transistor VT1. But EMF generated under the action of IR radiation by the photodiode BL1, in the amount of voltage the led is already enough to open the transistor. Thus, the transistor VT1 opened if the IR radiation reaches the photodiode, and closed if between photos and emitting diodes is the blade of the obturator.
When an open state of the transistor coincides with the positive half-cycle of current the excitation winding of the motor M1 projector, the resistor R2 is shunted circuit VT1VD3 synchronizer, the excitation current of the motor increases, the frequency of rotation of its shaft is increased. In case of equality of triple frequency shaft rotation frequency network is installed in the system and automatically supported in equilibrium. Zener diode VD4 limits the voltage at the collector of transistor VT1, protecting it from breakdown.
Neon lamp HL1 is used for visual monitoring of synchronization. Illuminated this lamp strobe marks on the grip frame projection in synchronous mode should appear stationary or slightly "wobble".
Transistor VT1 is composite, the allowable voltage collector-emitter 80 and In current of 1 a can be replaced by another similar or relevant United the transistors CTG and CTG. If a valid voltage collector-emitter applied to the transistor more than 100 V, the Zener diode VD4 can to exclude.
As And To the emitter and photodetector can be use relevant elements from devices remote control TVs, and neon lamp HL1 replace any two LEDs by turning them anti-parallel.
All the details of the synchronizer, with the exception of a neon lamp and resistor R1, mounted on Board, of foiled fiberglass, pripaivaya their findings to cut from foil "noses". Optical window emitting diode and V photodiode BL1 should be aimed at each other when the distance between them is not more than 5 mm. the Value set in the projector of the resistor R2 should be reduced to 75 Ohm.
A neon lamp is placed in a separate small case and provide connective the wires are long enough so that it could bring to stroboscopic labels.
Mount and connect the stabilizer to the projector, make sure the speed the projection is reduced in the presence of opaque obstacles between the IR emitter and a photodetector, increasing by its deletion. If not, try changing the distance between the elements of the opto-coupler, replace the led HL2 similar to another type or color of the glow, to select values of resistors R3-R5.
Having adjusted the sensor, charge synchronizer glued to the bottom of the hull the projector so that the shutter blades during rotation of the interrupted thread The infrared radiation between the diodes V and BL1.
Turning on the projector, adjust the timing by rotating the handle of the speed controller - variable resistor R1. For termination of the synchronizer enough to connect between socket 1 and 8 sockets SS projector. This jumper features included with the projector to the standard plug.
If in the process of shooting sync accidentally broken, this is clearly seen on hearing, it can be quickly fixed with a small twist of the arm knob speed. In the short video out of sync almost not affected.
It is very important to make a close-up of the movie on videotape when disabled automatic focusing of the camera. Otherwise the attempts of automation to compensate lack of clarity of movie images will drastically degrade the quality of the video. Disabling automatic, temporarily put on the silver screen any drawing or other clear high-contrast image and focus the camera manually. Before shooting do not forget to lubricate the moving parts of the projector and clean the manifold it engine.
The described device can be used with other projectors, equipped with brushed motors, for example, "Wave" or "Rus".
The proposed device, of course, synchronizes the projector with the frequency sweep of the camera, and with the frequency of the voltage in the AC network. However experience shows that the latter, at least in the big cities, in sufficient for the task at a level close to the nominal value (50 Hz) and stable.
Literature
Author: N. Khlopin, Kirov