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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Loud motor rotation modulator. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electric motors They just don’t come up with anything to attract customers to the store: flashing garlands on the windows, moving toys in the windows, continuously driving model trains or a bowing hare barker, a plywood cowboy politely taking off and putting on his hat, and many others. etc. Looking at all this, I just want to shout that the cowboy quickly takes off his hat, the hare bows more often, and the train goes faster. Maybe the blue bulbs of the garland will light up more strongly for whistling, and red ones for low sounds. If there was such control of the sounds of the environment, then the window would come to life when a car passed along the road nearby or two people stopped to talk among themselves. Such a funny attraction would serve as an additional attracting factor. A good decoration of the square would be a fountain that works to the sounds of the environment, which change not only its color lighting, but also the height of the water jet by changing the speed of rotation of the pump motor. The circuit that modulates the rotation of the micromotor by the volume of environmental sounds is shown in Fig.1. You can apply this circuit to power a microelectric motor that rotates a mirror ball with a Christmas tree installed on it through a gearbox.
The circuit contains a highly sensitive amplifier on a D1 chip and transistors VT4, VT6. A microphone from a hearing aid was used (the one in a metal rectangular case measuring 25x15x7 mm with a hole 3 mm in diameter). Even faint voices spoken at the farthest wall of the room from the microphone are picked up. From the output of the amplifier (from resistor R19), the signal is fed to any purchased or home-made color and music installation. Despite the high sensitivity, the amplifier is resistant to self-excitation and resistant to mains background. For this, filters R4, VD1 are applied; R9, C3, VD3; R13, C6; R14. The same voltage at the antiphase inputs of the D1 chip is set by resistors R3, R5. The engine is too inertial device and, in contrast to the loudspeaker, does not have time to respond to sound frequency electric current fluctuations. He can have time to respond to the loud component of the sound, which still needs to be highlighted. If you connect the engine to the output of a power amplifier, then the rotational speed of its shaft will not change when the amplitude of the output oscillations of the sound frequency changes, because their effective value (constant component) does not change. In order for the engine to respond to sound, it is necessary to highlight the lowest frequency component of the sound - volume fluctuations. The detection of the loud component of the sound is carried out by limiting the signal from below by the transistor VT4 and smoothing the received pulses with a filter on the diode VD2 and capacitor C1. Transistor VT4 limits due to the choice of its operating point near the saturation region. Therefore, the transistor VT4 in the initial state is maximally open and only works to close. The greater the volume (amplitude) of the signal, the stronger it closes, and it cannot open more strongly from the opposite polarity of the half-cycle of oscillations, since it cannot open more strongly than saturation. In the saturation of the transistor VT4, the output of the microcircuit does not short circuit to a common wire due to the presence of resistor R15. Thus, the transistor VT4 works with non-linear distortion as a limiter and amplifies only one half of the signal (one half-period of oscillations), the effective value of which varies depending on the amplitude of the oscillations, and the constant component of the signal voltage is reduced to zero. These non-linear distortions do not affect the operation of the color music set-top box connected in parallel with the resistor R19. On the potentiometer R2, the loud component of the signal is selected, which passes through the isolation capacitor C2 to the current amplifier, made on emitter followers on transistors VT3, VT5. The emitter follower on the transistor VT1 and the potentiometer R7 set the zero level of the output, i.e. the initial voltage on the engine, and consequently, the initial frequency of its rotation. Relative to the zero level, there is an increase in voltage and speed when sound appears. Capacitor C2 differentiates the oscillations passing through it, therefore, at a constant sound volume, the engine shaft speed approaches its original state. Its growth will occur with increasing volume. The emitter follower on the transistor VT1 improves the recharge of the capacitor C2, thereby preventing the smoothing of the selected loud component of the sound. Potentiometer R2 regulates the attenuation of the signal, i.e. it sets the amount of speed increase when the volume is increased. Transistor VT2 works as a compressor, compressing the dynamic response, and reduces the drift of zero, which occurs over time in the direction of increasing the speed. When the voltage rises on the motor M1, the transistor VT2 opens more strongly and reduces the voltage across the resistor R8, and consequently, the zero output voltage level. Capacitor C7 partially smoothes the noise from the engine, penetrating the input of the DC amplifier through the transistor VT2, reducing feedback on them. The microphone amplifier is powered from the power source of the color and music installation. It operates at a supply voltage of 9 to 30 V. With a different supply voltage than indicated in the diagram, it is necessary to select the value of the resistor R11 so that the operating point of the VT4 transistor is near the saturation region. In this case, the engine reacts as much as possible to an increase in sound volume. The microphone amplifier should be placed in a separate housing together with the BM1 microphone and connected to the color and music installation with three interlaced (bundled) wires. It cannot be placed in the body of the color and music installation, since it reacts to the rumble of the transformer, even inaudible to the ear, and thyristors induce electromagnetic interference. Even feels the hum of the power transformer across the table if they are both on the table. The DC amplifier block (the rest of the circuit, after the microphone amplifier) can be placed in the case of the color music installation, if there is space, or in a separate case. The potentiometer knobs must be brought out of the housing for adjustment. This block is powered from a separate transformer or from a special winding wound on the power transformer of the color and music installation with a wire with a diameter of more than 0,35 mm. The M1 motor is placed away from the microphone, connecting it with long wires to a DC amplifier through a connector of any type. The noisier the motor and gearbox, the farther away from them you need to place the microphone to eliminate feedback. It is desirable to close the motor and gearbox inside the driven object for better noise absorption. The engine can be replaced with MDP-1 or another similar one. When using a micromotor with a higher operating voltage, it is necessary to increase the supply voltage of the DC amplifier unit accordingly. When using a more powerful motor, the current indicated in the diagram will be exceeded and it will be necessary to install the VT5 transistor on the radiator and replace it with any more powerful one of the same conductivity, for example, KT805B. The microphone amplifier is operable without a DC amplifier unit. The setting comes down to selecting the value of the resistor R11 according to the maximum response of the engine to an increase in sound volume and the value of the resistor R17 so that the transistor VT2 starts to open slightly (the voltage across the resistor R8 begins to decrease) at the most frequently set zero level by the potentiometer R7. Those. the initial engine speed, which is most liked by the user, should determine the beginning of the opening of the transistor VT2. Then, with an increase in the engine speed, the transistor VT2 opens more strongly and reduces the voltage across the resistor R8 more strongly. To assemble the circuit quickly and with low labor costs, you can abandon printed circuit boards and use surface mounting in separate plastic cases. Figure 2 shows an example of such a design.
The microphone amplifier is assembled in a rectangular plastic box 1, in which a watch was sold. Microphone BM1 and capacitor C5 are glued to the side walls of the box 1. A lump of other parts, soldered together according to the scheme, lies freely in the box. If he hangs there a little and rumbles when shaking, then this does no harm to him, as long as the conclusions of the radio elements do not close, and they are quite rigid for this and will never close by themselves from blows if they are not closed during installation. For those that are flexible and soft, such as microphone leads, you need to put on an insulating tube. Soldering with a glued capacitor C5 and three output wires 2 attached to case 1 prevents the installation from moving around the box and closing with the metal case of the microphone. tube. If the wires are woven obliquely, then it is possible to make a loop 3 with any one wire near the inner side of the housing wall 1, which prevents the wires from being pulled out of the housing. The place of contact of the output wires with the side wall of the case is covered with glue. Hole 4 must be drilled in the case, coinciding with the hole of the BM1 microphone. Similarly, at a distance of 1 m from the housing of the microphone amplifier, a round plastic box 2 of cream or any other is fixed on its output wires 5. It also has a mounted DC amplifier unit assembled in it. Two potentiometers R2, R7 of type SP3-1a-0,25 are fixed on the lid or bottom of the box from the outside by pressing their leads into the plastic with a hot soldering iron. The leads that have passed through are bent inside the box, and together with the leads of large parts glued inside the box, they serve as reference contacts, on which surface mounting is performed. Convenient and beautiful handles for variable resistors are obtained from corks (lids) that cover toothpaste tubes. They can be glued to the resistors with epoxy. The upper part of the variable resistor is covered with a thin layer of plasticine, except for the swivel head with a slot for a screwdriver, which is immersed in the hole of the threaded plug, where epoxy is poured. Once cured, the epoxy resin securely adheres the cork to the head of the variable resistor. Its other fixed parts do not stick due to the applied plasticine, which, after fixing the handles, is easy to clean off. Wires 5 from the microphone amplifier enter one slot in box 2, and 5 wires come out from a diametrically opposite slot in the wall of box 5. Two wires were added, connected to an additional winding made on the power transformer of the color and music installation. The bundle of intertwined wires ends with a five-pin connector of any type, designed for connection to a color music installation. The wire lengths indicated in the drawing are not mandatory, but only an example. They can be increased several times until the self-excitation of the microphone amplifier occurs, which is eliminated by an increase in the capacitances of capacitors C3, C6, C8. In the diagram, the values of the capacitors are indicated with a margin. A transistor socket 5 is glued to the side wall of the box 9. It serves as a connector for the micromotor wires. Its conclusions are inserted into the holes drilled in the box and bent inside it. To prevent the lids of the boxes from opening spontaneously, pieces of PVC or rubber are glued to their inner surface of the side walls (where the lid contacts the rest of the box). Since the VT5 transistor heats up, for ventilation on the side wall of the box 5, at least two holes with a diameter of 4 mm must be drilled at diametrically opposite points of the round side surface. A microelectric motor from children's toys, controlled by the described circuit, easily copes with the rotation of a mirror ball made on the basis of a student's globe, with an artificial Christmas tree installed on it with shiny needles and a trunk length of 0,8 m. Author: V.Yu.Solonin
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