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Car seat position control device

The device is designed to memorize two positions of the car seat distance from steering column and backrest angle selected by the user, and their quick automatic installation. If necessary, it can control other objects that need to quickly translate in two specified situations, for example, the sunroof or turning the antenna.

The heart of the device is microcontroller PIC16F628A. During operation, move seat motor mounted on its shaft, the sensor produces pulses. The microcontroller counts these and the coincidence of the counted number with a predetermined stored in the nonvolatile memory, stopping the engine. The same is true for the control channel of the backrest.

The scheme of the control device depicted in Fig. 1. The channel sensor longitudinal movement of the seat consists of emitting IR diodeU1 (АЛ107А) and phototransistor VT1 (FT-2K). The sensor design shown in Figure. 2. Emitting diode 2 and the phototransistor 3 are separated are mounted on the shaft 1 by a metal disk with holes. When the IR radiation through the hole in the disc reaches the phototransistor, the voltage between its emitter and collector is reduced to 0.8 V or less.

1

Figure. 1

The number of holes in the disk should not be less than 10, but such that the total number of pulses for the full passage of the seat from one extreme position to the other does not exceed 16777215. The pulses arrive at the input RA0 of the microcontroller, which, under their reading, determines the position of the seat and generates commands to control the motor M1.

Fig. 2

Fig. 2

Switch the voltage supply of the engine is assembled on transistors VT8, VT10, VT12 and VT13. The node of the transistors VT4, VT5 prevents the simultaneous opening of all of the transistors switch, the possible failure of the microcontroller or an error in his program.

When the chair must remain stationary, the microcontroller sets the outputs RA2 and RA3 low voltage levels. The potentials of the bases and emitters of transistors VT4 and VT5 same, so that both transistors are closed. Closed and all transistors switch, so the voltage to the motor M1 is not received, and it is not working. The situation is similar in case of emergency simultaneous presence of high levels at the outputs RA2 and RA3.

When the chair you want to move, the microcontroller sets the outputs RA2 and RA3 are different levels: RA2 — low, RA3 — high to move forward: RA2 — high RA3 on low to move backward.

Когда подана команда “Вперёд”, открывается транзистор VT5, а за ним транзисторы VT10 и VT12. Транзисторы VT4, VT8 и VT13 остаются закрытыми. В результате левая (по схеме) щётка дви­гателя М1 соединяется с общим прово­дом, а правая — с плюсом источника питания (при условии, что зажигание выключено и транзистор VT3 открыт). Вал двигателя вращается в сторону, соответствующую перемещению крес­ла вперёд.

При команде “Назад” откроются транзисторы VT4, VT8, VT13, а транзис­торы VT5, VT10, VT12 закроются или останутся закрытыми. К двигателю М1 будет приложено напряжение питания в противоположной предыдущему слу­чаю полярности. Его вал станет вра­щаться в сторону, соответствующую перемещению кресла назад.

The same is true for the control channel seat recline. The rotation sensor of the motor shaft of this channel consists of the emitting diode and phototransistor VD2 VT2. Its signal is fed to the input RA5 of the microcontroller. The decrease in the slope of the microcontroller sets the high level output low RA6 and RA7 output. Increasing slope — low level on RA6 and RA7 high. The switch of the motor M2 is assembled on the transistors VT9, VT11, VT14, VT15 node protection on the transistors VT6 and VT7.

Напряжение питания +12 В должно быть подано на устрой­ство управления постоянно (до замка зажигания). В его отсут­ствие перемещать кресло или его спинку вручную не рекомен­дуется. Это может потребовать повторного налаживания систе­мы. Транзистор VT3 блокирует узел коммутации двигателей привода кресла при включённом зажигании, предотвращая этим перемещение кресла и его спин­ки во время движения автомобиля. При включённом зажигании с кон­такта “Заж.” в цепь базы этого транзис­тора структуры р-п-р поступает напря­жение +12 В, в результате чего он за­крыт и напряжение питания на узел коммутации двигателей не поступает. При выключенном зажигании напряже­ние на контакте “Заж.” становится нуле­вым. Транзистор VT3 в этом случае открыт, и питание коммутаторов двига­телей включено.

The electronic unit is assembled on the breadboard surface mounting (Fig. 3). Transistors VT3 and VT8—VT15 necessary heat. I used aluminum plate with dimensions 60x50x8 mm, on which the two sides through mica strips cemented the transistors VT8—VT15. On another plate mounted transistor VT3.

Fig. 3

Fig. 3

On Figure. 4 shows a switching diagram of the motors of the chair with a relay. Transistors VT4—VT15 (according to the scheme of Fig. 1) and related details in this case are not required. The transistor VT3, and re-installed the transistors VT4—VT7 work without heat sinks. Relay K1—K5 — motor 90.3747 or 75.3777 with changeover contacts. As a K1 you can apply relay 90.3747-10 or 75.3777-10 with normally open contacts. In both cases, the device microcontroller running the same program.

Fig. 4

Fig. 4

Provides a soft limit range of motion of the chair and its backrest, which eliminates the need for limit switches. Before first turning on the circuit to manually slide the seat back until it stops, and its back swing it back until it stops. After power up, the device will operate only button SB4 and SB6, which specifies the movement of the seat forward, and its back — downward tilt. Button SB5 and SB7, specifying the displacement, respectively the chair and its back in the opposite direction, will be activated only after a small (five pulses of the sensor) move in the forward direction. When the button is pressed move in one direction, locks the button to move in the opposite direction.

Use the button SB4 move the seat forward almost all the way. Click SB8 will keep in memory of the microcontroller that position. The button should be hold down until you hear a signal given by the alarm HA1. After this, the chair moves forward for a set end point will be impossible. A similar operation run from the back of the chair, using the buttons SB6 (decreasing slope) and SB9 (memory stop).

To cancel previously set on the endpoint, briefly press (do not hold) the button SB8 (chair) or SB9 (back). A beep will confirm that the cancellation endpoints took place and you can record a new one. Button SB8 and SB9 must be accessible only to the specialist, to establish a system of governance chair, and protected from accidental clicks.

Then, using the buttons SB4—SB7, install the seat position, which will be the first fixed. After this short, no hold, press the button SB1. Included will be a beep, then press the SB2 button and hold for about 3 seconds, until the signal stops. Position 1 stored in the memory. Further buttons SB4—SB7 place the chair in the future the second fixed position, short press the SB1 button, and the beeping sound, press and hold the end signal button SB3. Position 2 stored in the memory.

Now you can always (but only when the ignition is off), set the chair and backrest are in arbitrary positions, in position 1, pressing the button SB2, or in position 2 by pressing the button SB3. The pressure should be short-lived. The program will automatically detect the desired direction of movement and moves the seat and backrest to the desired position.

All the information about the movements of the dental chair, his current position and target point is stored in the EEPROM of the microcontroller. At power-up, it is transferred to the RAM. When the power is off, change the position of the seat and its back is not recommended.

Firmware microcontroller

Author: A. GOETHE, Ryazan
Source: Radio №2, 2016

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One Comment

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">class="comment byuser comment-author-aleksandr53 even thread-even depth-1">

In this device the pulse sensor is fixed to the motor shaft and the screw transmission screw-nut, it's easier to count the number of pulses per unit (inch) promotion and rather stop. For the record, the engine transmits the rotation to the gearbox, but the gearbox rotates the gear screw-nut which in turn moves the chair.

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