RU57494U1 - EDUCATIONAL INSTALLATION FOR LABORATORY WORKS ON MECHANICS - Google Patents

Abstract

The utility model relates to educational and demonstration devices and is designed to perform laboratory and demonstration work in physics, in particular in the "Mechanics" section, provided for by the curriculum of secondary schools and higher educational institutions. The task to which the proposed utility model is directed is to create a simple and universal installation that allows one to perform most of the fundamental experiments in mechanics on it. In a training facility for laboratory work in mechanics, containing a measuring unit 1 mounted on a tripod and an electronic signal conversion unit 2, it is new that the measuring unit 1 is a device for converting linear and angular displacements into electrical impulses and includes an optical chopper 7 mounted on one end of the shaft 5, on the other end of which is attached a device for communication with the object under study, while the outputs of the measuring unit 1 are connected to the inputs electronically of the unit 2, which outputs are inputs serial COM port of the computer. The optical chopper 7 consists of a disk 8 with radial slots 11 at its periphery and an optical pair 9, and the device for communication with the object under study is a pulley 10. The electronic signal conversion unit 2 contains two branches, each of which includes a Schmit trigger 12 and a microcircuit (MS) converting the voltage level to the level of the serial COM port of the computer, while the inputs of the electronic unit 2 are the outputs of the optical chopper 7 according to the signals about the magnitude and direction of movement of the following object. 1 n.p.f.p.m., 3 s.p.f.p.m., 3 ill.

Description

The utility model relates to educational and demonstration devices and is designed to perform laboratory and demonstration work in physics, in particular in the "Mechanics" section, provided for by the curriculum of secondary schools and higher educational institutions.

A known installation for laboratory work on the course "Theory of elasticity and plasticity" (RF patent No.2012063, IPC G 09 B 23/06, publ. 04/30/1994) containing a power support frame in the form of a two-tier spatial frame with support legs of adjustable height. On the upper tier of the frame, support posts with a screw mechanism for vertical displacement of the supports are installed, which allow fixing the plate, and on the lower tier are measuring instruments with extension rods. The support column is a fork having through threaded holes for the stud and mounting bolts. To measure the deflections of the plate, dial gauges are used.

A known laboratory setup for demonstrating the laws of dynamics of uniformly accelerated movement (application No. 97121267, IPC G 09 B 23/06, publ. 09/27/1999), consisting of loads with overload connected by means of a thread thrown across the block, and a reference system of equal time intervals fixed on a common rack, in which it is new that the load having overloads consists of the upper and lower studied masses connected in series with each other by a torn electromagnetic coupling connected to a time relay connected in series to communication power supply circuit, the installation contains a start button and a limit switch located at the junction of the separated masses moving only along the vertical guides, in the lower part of which there is an electromagnet, and in the design section of the upper part - a spring

an indicator of the final speed of the lower detachable mass, in the lower part of which there is a contact breaking the power supply circuit of the electric stopwatch.

A known laboratory installation (application No. 93007409, IPC G 09 B 23/06, publ. 08/10/1995) containing a base, a horizontal beam in the supports, a vertical rod covered by a spring, an electric motor, a spring-loaded telescopic rack, writing devices. The installation can be used in all higher education institutions.

Known laboratory installation in mechanics (patent No. 2063064, IPC G 09 B 23/06, publ. 06/27/1996), designed to determine the coefficient of sliding friction in the rest and movement modes, containing a platform mounted for rotation on the shaft of the gearbox and associated with tachometer. One of the samples is made in the form of a disk and mounted on the platform by screws, the other sample is made in the form of a plate and mounted in a mandrel. The measuring device is a dynamometer. The block is placed on the rack, while the cable is connected at one end to the mandrel and the other to the bowl.

The well-known laboratory modular complex “Physical Fundamentals of Mechanics” was developed at INTOS OJSC and is intended for laboratory work at the Physics course, section “Mechanics” in higher education institutions (leaflet of INTOS OJSC, Russia 111024, Moscow , Aviamotornaya St. D.50, p. 1 "INTOS"), adopted for the closest analogue. The complex consists of nine installations and an electronic unit for conducting a laboratory workshop by the front-end method, using the block-modular design of the installations, which ensures their prompt assembly (disassembly). For a consistent method of organizing a laboratory workshop, each installation is equipped with an electronic unit. A computer measuring unit allows the simultaneous connection of two sensors of physical quantities. The inputs are designed to measure voltage and connect sensors of temperature, pressure, humidity, angular

speed, conductivity, pH sensor, magnetic field, optoelectric moment sensors and others. However, this laboratory modular complex provides for each laboratory work a separate installation with its own electronic unit, which complicates the laboratory work, maintenance of the entire complex, in addition, the costs of its purchase by schools and operation increase.

The task to which the proposed utility model is directed is to create a simple and universal installation that allows one to perform most of the fundamental experiments in mechanics on it.

The technical result, which the proposed utility model is aimed at, is to expand the functionality, increase the accuracy and speed of the installation.

The technical result is achieved in that in a training installation for laboratory work in mechanics, containing a measuring unit mounted on a tripod, and an electronic signal conversion unit, it is new that the measuring unit is a device for converting linear and angular displacements into electrical pulses and includes an optical chopper mounted on one end of the shaft mounted in the housing on a tripod, on the other end of which is mounted a device for communication with the test object ktomu, wherein the measuring unit outputs connected to inputs of an electronic signal converting unit, whose outputs are the inputs serial COM port of the computer.

An optical chopper consists of a disk with radial slots along its periphery and an optical pair.

The device for communication with the test object is a pulley.

The signal conversion electronic unit contains two branches, each of which includes a Schmit trigger and a microcircuit (MS) for converting the voltage level to the serial level

COM port of the computer, while the inputs of the electronic signal conversion unit are the outputs of the optical chopper according to the signals about the magnitude and direction of movement of the investigated object.

Schmitt's trigger is made on complementary field effect transistors - metal - oxide - semiconductor (CMOS).

The microcircuit for converting the voltage level to the level of the serial COM-port of a computer is made on an optical isolator.

The essence of the utility model is illustrated in figure 1 - figure 3, where:

Figure 1 - educational installation for laboratory work in mechanics (a - front view, b - top view).

Figure 2 - view A of figure 1 (a - side view of the optical chopper, b - the peripheral part of the disk - view B).

Figure 3 is a functional diagram of an electronic signal conversion unit.

4 is a schematic diagram of an electronic signal conversion unit (example of a specific implementation).

Here: 1 - measuring unit; 2 - electronic unit; 3 - tripod; 4 - case; 5 - shaft; 6 - bearing; 7 - optical chopper; 8 - disk optical chopper 7; 9 - optical pair; 10 - a pulley; 11 - slots; 12 - Schmitt trigger; 13 - microcircuit (MS).

An educational installation for laboratory work in mechanics (Fig. 1) contains a tripod 3, on which a measuring unit 1 and an electronic signal conversion unit 2 are fixed. The measuring unit 1 includes an optical chopper 7, consisting of a disk 8 with radial slots 11 along its periphery ( fig.2b) and an optical pair 9. The disk 8 is mounted on one end of the shaft 5 mounted in the housing 4 on the bearings 6, and the housing 4 is mounted on a tripod 3. At the other end of the shaft 5 is attached a device for communication with the object being studied, in particular a pulley Outputs KSR Control unit 1 through 9, a pair of optical inputs are connected to the electronic signal conditioning unit 2, which outputs

are the inputs of the serial COM port of the computer. The measuring unit 1 is a device for converting linear and angular displacements into electrical pulses.

The electronic signal conversion unit 2 (Fig. 3) contains two branches, each of which includes a Schmit trigger 12, which converts the signal from the measuring unit into a digital signal and a microcircuit (MS) 13 for converting the voltage level to the level of the serial computer COM port, when this inputs of the electronic unit 2 are the outputs of the optical chopper 7 according to the signals about the magnitude and direction of movement of the investigated object, which are: a set of goods; Oberbek's pendulum; physical pendulum; strip with magnetic strips; fluoroplastic bar with magnetic stripes; steel balls; a set of two goods and overload connected by an inextensible thread; overload ring; set of two elastic and one inelastic ball.

The training facility is able to track linear and angular displacements in dynamics and convert through an optical chopper into electrical impulses. The operation of the installation is based on measuring the angle of rotation of the pulley 10 of the measuring unit 1 and the time during which this rotation occurred.

The optical chopper 7 (figure 2) is a disk 8 with radial slots 11 at its periphery and an optical pair 9 - an IR (infrared) emitter (VD1) and an infrared photodetector (VD2) of two photodiodes (figure 4).

When turning the pulley 10 of the measuring unit 1, the optical chopper 7 (disk 8 with slots 11 - fig.2b) passes or delays the beam that emits an IR emitter and receives an infrared photodetector (VD2). As a result of this, a signal is generated from the photodetector (VD2) with a flat front and a slice. A pulse with a noisy, unformed front and cut is not suitable for switching digital devices. To bind the switching moment to a certain threshold level of the input pulse

use the Schmitt trigger circuit 12, consisting of a two-stage amplifier covered by weak positive feedback (microcircuit DD1.1 - DD1.2, DD1.4 - DD1.5) (Fig. 4). Schmitt trigger 12 in this circuit is used as threshold devices and shapers of rectangular pulses from arbitrary waveforms, including sinusoidal ones. DD1.3 and DD1.6 are used as amplifiers. The K561LN1 (DD1) microcircuit is made according to CMOS technology (on complementary field effect transistors - metal - oxide - semiconductor) and operates on a voltage of +12 volts, at the logic outputs of which rectangular pulses with a range from 0 to +8 volts are formed.

The computer's COM port standard uses single-ended transmitters and receivers — the signal is transmitted relative to a common wire — circuit ground. The logical unit corresponds to the voltage at the input of the receiver in the range -12 ...- 3V. Logical zero corresponds to a range of +3 ... + 12V. For compatibility of the signal of the Schmitt trigger 12 with the logic of the COM-port of the computer, a voltage level converter (microcircuit 13) made on the AOT101AC optical isolator (microcircuit MS DD2) is used.

The signals from the optical chopper 7, converted by the electronic unit for converting signals 2 into computer-readable signals, are fed to the inputs of the COM port of the computer 12 via two channels (OUT (1) and OUT (9) (Fig. 4) and processed programmatically according to the assignment of the laboratory work.

When the shaft 5 of the measuring unit 1 is rotated, pulses are formed at its outputs corresponding to the opening or closing of the optical pair 9 (IR infrared emitter (VD1) and IR photodetector (VD2).

The disk 8 of the optical chopper 7 has 90 slots 11, made through 4 degrees, while 4 cases are possible: both photodiodes of the photodetector VD2 are illuminated by the emitter VD1; the first is highlighted, and the second is not; the second is highlighted, but the first is not; both are shaded. Therefore, you can track the movement of the breaker in one degree, and the alternation of output

information makes it possible to determine the direction of movement, which allows the reading of motion parameters during the entire movement of the investigated object during the experiment.

Example 1. Laboratory work "Measurement of the acceleration of free fall using a mathematical pendulum."

In the work, it is necessary to determine the acceleration of gravity, knowing the parameters of the mathematical pendulum: the length of the thread and the period of oscillation. Then from the formula

we find

g = l4π ² / T ²

where l is the length of the thread;

T is the oscillation period of the pendulum;

π = 3.14 (mathematical constant).

The length of the thread l is determined by direct measurement using a ruler. To determine the period of oscillation of the mathematical pendulum, we use the measuring unit of the kit. Why do we suspend the pendulum on the pulley of the measuring unit and use the method of deflection to some small angle (5-7 degrees) to bring it out of equilibrium. In this case, the pendulum begins to make periodic oscillations, dragging along the pulley of the measuring unit (without slipping). The movement of the pulley connected by an optical chopper is controlled by a computer. Using a computer program, the movement of cargo is monitored both from right to left, and in the opposite direction. The time between changes in the direction of cargo movement at the points of maximum deviation from the equilibrium position is the period of the mathematical pendulum. Based on the analysis of data taken from the installation, the computer programmatically determines the time equal to the period of oscillation using an internal timer. In this case, the subjective factor of accuracy of time measurement is completely excluded.

Example 2. Laboratory work "Measurement of spring stiffness."

The elastic force arising from the deformation of the body is proportional to its elongation and is directed opposite to the direction of movement of the particles of the body during deformation.

F _control = -k x

x - spring extension

k is the coefficient of proportionality, called the stiffness of the spring.

According to the theory, the extension of the spring will be proportional to the acting force, in this case, the gravity of the suspended loads mg. Thus, to determine the stiffness of the spring, it is necessary to know the effective force (the number of suspended loads) and measure the elongation of the spring (x). To determine the extension of the spring, we use the measuring unit of the kit. The device allows you to register the angular movement of the pulley with an accuracy of 1 degree, which corresponds to the linear displacement (x) of the thread through the pulley in 0.19 10 ^-3 m. When the mass of the suspended load increases each time, the computer, according to the established program, calculates the spring extension and spring rate : K _i = F _control / x _i

Claims (6)

1. Training facility for laboratory work in mechanics, comprising a measuring unit mounted on a tripod and an electronic signal conversion unit, characterized in that the measuring unit is a device for converting linear and angular displacements into electrical impulses and includes an optical chopper mounted on one the end of the shaft, on the other end of which is attached a device for communication with the test object, while the outputs of the measuring unit are connected to the inputs of the electronic unit and converting the signals whose outputs are inputs serial COM port of the computer. 2. The training installation according to claim 1, characterized in that the optical chopper consists of a disk with radial slots along its periphery and an optical pair. 3. The training installation according to claim 1, characterized in that the device for communication with the test object is a pulley. 4. The training installation according to claim 1, characterized in that the electronic signal conversion unit contains two branches, each of which includes a Schmit trigger and a microcircuit for converting the voltage level to the level of the serial COM port of the computer, while the inputs of the electronic unit are optical outputs breaker for signals about the magnitude and direction of movement of the investigated object. 5. The training installation according to claim 4, characterized in that the Schmitt trigger is made on complementary field effect transistors - metal - oxide - semiconductor. 6. The training installation according to claim 4, characterized in that the microcircuit for converting the voltage level to the level of the serial COM port of the computer is made on an optical isolator.