Diploma project of modernization of low-frequency physiotherapy apparatus

Contents

Introduction

1 Method Overview

1.1 Dosimetry and procedure technique

1.2 Therapeutic techniques

1.3 Readings

2 PCB Manufacturing Technology

2.1Basic Manufacturing Techniques

2.2 Fabrication of base holes

2.3 Lamination

2.4 Exposure

2.5 Chemical treatment

2.6 Pressing

2.7 Hole Drilling

2.8 Hole Metalization

2.9 Chemical treatment

2.10 Application of protective coating

3 Low-frequency physiotherapy apparatus

3.1 Purpose of the set

3.2 Technical data

3.3 Arrangement and Operating Principle

3.4 Indication and control unit

3.5 Design Part

3.6 Calculation of temperature in the center of heated zone

3.7 Apparatus design

3.8 Indication of safety measures

3.9 Preparation of the apparatus for operation

4 Economic justification of the project

4.1 Summary

4.2 Characteristics of the advanced apparatus

4.3 Market Research and Analysis

4.4 Marketing Plan

4.5 Production Plan

4.6 Potential Risks

4.7 Financial Plan

5 Life safety and environmental friendliness of the project

5.1 Analysis of hazardous and harmful factors during operation of the device

5.2 Microclimate in physiotherapeutic room

5.3 Calculation of protective grounding

5.4 Calculation of artificial lighting

5.5 Fire safety measures

Conclusion

List of sources used

Introduction

The diploma project presents the technical documentation developed for the modernization of the low-frequency physiotherapy apparatus. The project has chosen the concept of modernization, developed a drawing of a general view of the apparatus, drawings of the most important functional units and electrical diagrams. The explanatory note contains descriptions of the device and work, guidelines for maintenance, as well as issues of economic justification of the modernized apparatus and safety and environmental friendliness of the project.

2.2 Fabrication of base holes

At this stage, a set of base holes is made in the workpiece. The type and size of these holes depends on the selected basing system (see location system section). Usually, the base holes of a round shape are made by drilling, and an oval you-wheelhouse. Ensuring maximum accuracy of basic holes manufacturing at this stage will ensure normal alignment of layers and holes in subsequent stages.

2.6 Pressing

At this stage, the board is assembled into a package consisting of internal and external layers laid by a prepreg (material serving as glue). At the boundaries of the package, it is necessary to use additional layers to protect the press plates from ingress of molten prepreg and ease of disassembly of the package. Pressing is carried out in a vacuum in several stages, first at relatively low forces (at certain temperatures), then at high forces and high temperatures. The boundary point is the gelation point of the prepreg. The correct determination of this point is very important, since if the 2nd force is applied to the gelation point, the preform will contain voids, and if after, the prepreg will transition to a glassy state and its painting will be pro-isolated.

2.8 Holes metallization

This step serves to coat the opening with a thin layer of metal. The problem is that the surface of the hole is non-conductive. For metallization, the board is placed in a bath, where the board is completely chemically covered with a thin layer of paladium. The essence of the process is chemical and as a result, both dielectric and metal surfaces are coated.

2.10 Application of protective coating

To protect the board surface, where soldering is not required in the future, a mask is applied. There are several types of masks and methods of applying them. The photosensitive mask is applied in the same manner as the photoresist and provides high accuracy of the process. Stenciling does not have such accuracy, but the mask material is more plastic and the cost of the process is lower.

2.11 Relief boards

One of the tasks in the manufacture of modern printed circuit boards is to significantly increase the switching (tracing) capabilities of the PCBs. The main directions of fulfilling this requirement were to reduce the routing step (the minimum distance between the centers of conductors of conductive layers) and increase the number of conductive and insulating layers.

Reducing the routing step has the following disadvantages: complicating and increasing the cost of technological processes (improving the accuracy class of PCB production); significant reduction of tracing step slightly increases tracing capabilities. This is because the transitions cannot be substantially reduced, and each of them usually has more contact pads on the conductive layers than the transitions themselves.

Increasing the number of layers has the following disadvantages: significant complication, increase in cost and increase in the PP production cycle; reduction of percentage yield of suitable PP; reduced reliability of PP. As a result of the search for an alternative to improve the switching capabilities of the PCB, a relief board ( TD) design was developed.

3.1. Set Assignment

3.1.1 Low-frequency physiotherapy apparatus is designed for therapeutic action with modulated sinusoidal currents of sound frequency. device is intended for application in physiotherapeutic rooms of medical institutions.

3.1.2 Operating conditions:

- ambient temperature from 10 to 35 ° С;

- relative air humidity up to 80% at a temperature of 25 ° С;

-atmospheric pressure from 86 to 106 kPa (from 650 to 800 mm Hg);

- supply network voltage (220 + 22) V, 50Hz.

3.3.3. Electrical Schematic Diagram Description

3.3.3.1. Elements of the entire electrical circuit of the apparatus are located on separate printed circuit boards and inside the apparatus housing.

The electrical circuit diagram of the apparatus is divided into separate electrical circuits of devices, which are made in the form of printed circuit boards with detachable connections.

The main electrical diagrams of the apparatus include:

- circuit diagram of the apparatus;

- initial electrical circuit of the indication device;

-additional electrical circuit of control generator

codes;

- initial electrical circuit of the generator;

- initial electrical circuit of the timer;

- initial electrical circuit of voltage stabilizer;

- initial electrical circuit of the connecting device.

3.3.3.3. Timer

The timer board contains:

counter - divider "I: 60" (DI, 2, D5.3, D5.4, D9, DII.I);

subtracting counter (D4, DI7);

installation counter (DI.4, D2, DIO, DI9);

start-up and release diagram (Dl.2, DI.3, D3; D5.I;D6.I);

sound signal generator (D6.2, DI6, DII.2, DI8.2, VT3);

patient current switch DI5;

power amplifier (D8, DI2 DI4, VTI, VT2).

The divider counter "I: 60" is set to "O" when power is turned on and is in a stalled state. When START button is pressed, "log" level appears on D3.2 flip-flop pin 13 synchronously with I Hz signal front. I "with a delay of one clock cycle of I Hz. Level "log. I "appears on the CE of counter D9 and allows the pulse count. The division coefficient of the first counter D9 is equal to 15, the second counter additionally divides -by 4 the frequency of the output pulses of the decoder DII.I, as a result, the period of the output pulses of the second counter D9 is equal to one minute.

The subtracting counter D 4 and DI7 in the initial state operates in the parallel recording mode, recording the output code of the setting counter D2 and DI0. When START signal "log. On output 12 of flip-flop D3.2, counters D4 and DI7 at input of PE are put into subtraction mode, at that subtraction is performed from time set in counter of setting D2 and DIO, for one minute for each clock pulse coming to inputs of counter, and at the same time valve D5.I passes signal of timer operation indication. Subtraction occurs as long as the content of the counter becomes 0; at the same time at the exit FROM the DI7 counter there is an impulse of a loan and makes installation in 0 D3.I, D3.2, D6.I triggers of the scheme of start-up which blocks the D9 counter, transfers the counter of D2 and DI0 installation and the subtracting D4 and DI7 counter to the mode of parallel record at which at the outputs of the subtracting counter zero register.

Under the action of the pulse-induced DI7 counter lock-in, the difference from 0 to I at the output 2 of the D6.I flip-flop is D6.2. transitions to the log state. I "and allows the audio signal to pass to the transistor VT3 through the matching circuit DII.2 and one-time removes the prohibition from the counter DI6, which, after eight periods of the frequency I Hz, returns the trigger D6.2 to the log state. O "thereby terminating the sound signal.

The current switch DI5 at the time of the sound signal, i.e. after the prescribed procedure time, you give the "log" level at the output 12 DI5.2. O, "which, acting on a ten-bit meter in the generator board, smoothly turns off the patient's current.

The DI5.2 flip-flop drop from I to 0 is synchronized at input C with the signal determining the beginning of the pause.

The power amplifier is designed for power amplification of sinusoidal-modulated signals generated by digital and analog devices of the apparatus, and isolation of the patient's circuit by means of an output transformer from power and other circuits of the rest of the apparatus circuit.

Power amplifier is made according to two-stroke transformer circuit with negative feedback. In each arm of output stage of amplifier composite transistors of the same type of conductivity are used, in collector circuits of which symmetric primary winding of output transformer is connected.

One of the composite transistors of each arm of the output stage of the power amplifier (VTT and VT2) is located in the 4.254 board, and powerful transistors are located on the rear wall of the apparatus. The transistors VTI and VT2 are excited by the same operational amplifiers DI2, DI4, but are excited antiphasically due to the fact that the amplifier DI2 is turned on as inverting, and the amplifier DI4 as non-inverting.

Each operational amplifier DI2, DI4 is covered by negative feedback via circuits RII, R18 and R13, RI9, respectively. The offset to the output transistors VTI and VT2 is supplied through the non-inverting inputs of the operational amplifiers DI2, DI4 from the bias stabilizer, the current source of which is made on DI3 according to the "current mirror" scheme. The actual bias voltage stabilizer is located in close proximity to the powerful output transistors on the rear wall of the apparatus and has thermal contact with them, as a result of which the bias stabilizer also plays the role of temperature stabilization of the initial current of the output transistors.

Input circuits of operational amplifiers DI2, DI4 are combined in pairs, one of them is the actual input of the amplifier, the second is the input of negative feedback, covering the entire amplifier.

Feedback is supplied from feedback winding of output transformer.

3.4 Indication and control unit

In this diploma project, it was decided to improve the indication unit by replacing standard board products with microcontrollers from the PIC16 series. This allowed the LCD monitor to be mounted to display current information about current processes. A more convenient interface made it possible to optimize treatment processes, increased usability, patient and operator comfort. Electrical schematic diagram is shown on poster 200402.160010.000 E3

On a payment are located the counter with the decoder of the switchboard of a sort of works D2, the scheme of initial installation (D I.I - Dl.3, RI, CI), the highlighter of childbirth of works "4" and "5" (the DI.4 I D4.4), the LED indicators displaying a condition of the switchboard of a sort of works of VD2 VD6, inverting converters of D3.2D3.6 level, the sI button.

At the moment of power-on, the initial setting circuit generates a pulse with a log level. I "and, acting on the input R of counter D2, sets it to the state" all 0, "except for output 2, on which" log. I, "which corresponds to the type of work" I, "At the same time, the prohibition level" log.1 "comes to the CE permission input, and pulses with a frequency of I Hz come to the counting input, but since the log is at the CE input. I, "the counter does not change its state.

When the sI button is pressed, the permission signal ("log. 0 "), via the split connection XI (pin 16) enters the input CE of the counter D2, and the counter begins to change its states until the button sI is released. When the button is released, the status of the counter will be fixed.

The D6 multiplexer and the VD13 VD18 light emitting diodes perform the functions of decoding and indicating the states of the modulation coefficient switch, and the D7 multiplexer and the VD19 VD25 diodes perform the functions of decoding and indicating the states of the modulation frequency switch .

Logic circuits D4.I- D4.3 are the state decoder of electronic duration switch D5.4- D5.6 - level converters, VD10 VD11 - status indicators of duration switch, D5.I- D5.3, VD7 VD8 - level converters and current range switch indicators.

D8, DI I, H3 chips are used to decrypt and indicate tens of minutes of a procedural timer, D10, DI2, H4 - units of minutes of a procedural timer.

H I, H2, H5 - sign indicators of patient current meter.