Contactless lighting control. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Lighting

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As soon as a guest crosses the threshold of your apartment, as if by magic, light flashes in the hall, illuminating the twilight, usually characteristic of the hallway at any time of the day. And the whole point is in the rug that lies inside the apartment near the front door, or rather, in the sensitive antenna hidden under it, or more precisely, in the electronic machine that controls the lamp in the hallway.

The automaton (Fig. 1) is assembled on only two digital microcircuits (DD1 and DD2), one transistor (VT1) and one trinistor (VS1). It contains a pulse generator built on logic elements DD1.2-DD1.4, capacitor C7 and resistor R10, and generates rectangular pulses with a frequency of 10000 Hz (or 10 kHz is the audio frequency). Moreover, the stability of the frequency does not matter much. Therefore, the repetition period of these pulses is 0,1 ms (100 µs). These pulses are practically symmetrical, so the duration of each pulse (or pause between them) is approximately equal to 50 μs. On the logical elements DD1.1, DD2.1, capacitors C1-C3, resistors R1, R2, diode VD1 and antenna WA1 with connector X1, a capacitive relay is made that reacts to the capacitance between the antenna and the network wires.

(click to enlarge)

When this capacitance is insignificant (less than 15 pF), rectangular pulses of the same frequency of 1.1 kHz are formed at the output of the DD10 element, but the pause between them is reduced (due to the differentiating chain C1R1) to 0,01 ms (10 μs). It is clear that the pulse duration is 100 - 10 = 90 µs. However, in such a short time, the capacitor C3 still manages to be almost completely discharged (through the diode VD1), since its charging time (through the resistor R2) is long and approximately equal to 70 ms (70000 μs). Since the capacitor is charged only at a time when there is a high voltage level at the output of the DD1.1 element (whether it be a pulse or just a constant level), during a pulse with a duration of 90 μs, the capacitor C3 does not have time to noticeably charge, and therefore a high voltage level remains at the output of the DD2.1 element all the time.

When the capacitance between the WA1 antenna and the network wires increases (for example, due to the human body) to 15 pF or more, the amplitude of the pulse signal at the inputs of the DD1.1 element will decrease so much that the pulses at the output of this element will disappear and turn into a constant high level. Now capacitor C3 can be charged through resistor R2, and a low level is set at the output of element DD2.1. It is he who starts the single vibrator (waiting multivibrator), assembled on the logic elements DD2.2, DD2.3, capacitor C4 and resistors R3, R4.

While the capacitance of the antenna circuit is small, due to which there is a high voltage level at the output of the DD2.1 element, the single vibrator is in a state in which the output of the DD2.2 element will be low, and the output of DD2.3 will be high. The time-setting capacitor C4 is discharged (through the resistor R3 and the input circuit of the element DD2.3). However, as soon as the capacitance increases markedly and a low level appears at the output of the DD2.1 element, the single vibrator will immediately generate a time delay, at the indicated ratings of the C4R3R4 circuit, equal to approximately 20 s. Just at this time, a low level will appear at the output of the DD2.3 element, and a high level will appear at the output of DD2.2. The latter is able to open an electronic key made on the logic element DD2.4, transistor VT1, diode VD3 and resistors R5-R8. But this key does not remain open all the time, which would be clearly inappropriate both in terms of energy consumption and, most importantly, because of the completely useless heating of the control transition of the VS1 trinistor.

Therefore, the electronic key is activated only at the beginning of each half-cycle of the network, when the voltage across the resistor R5 increases once again to approximately 5 V. At this point in time, instead of a high voltage level, a low voltage appears at the output of the DD2.4 element, due to which the transistor VT1 opens first, and then the trinistor VS1.

But, as soon as the latter opens, the voltage on it will decrease significantly, due to which the voltage at the upper (according to the circuit) input of the DD2.4 element will decrease, and therefore the low level at the output of this element will again abruptly change to a high one, which will cause automatic closing of the transistor VT1. But the trinistor VS1 will remain open (on) during this half-cycle.

During the next half-cycle, everything will repeat in the same sequence. Thus, the electronic key opens only for a few microseconds required to turn on the trinistor VS1, and then closes again once again. Due to this, not only the power consumption and heating of the trinistor are reduced, but also the level of radiated radio interference is sharply reduced.

When the 20-second exposure ends, and the person has already left the "magic" rug, a high level appears again at the output of the DD2.3 element, and a low level appears at the output of DD2.2. The latter locks the electronic key through the lower input of the element DD2.4. In this case, the transistor VT1, and hence the trinistor VS1, can no longer be opened (according to the upper input of the DD2.4 element in the diagram) by synchronizing network pulses. If the shutter speed has expired, but the person is still on the mat (on the WA1 antenna), the electronic key will not lock until the person leaves the mat.

As can be seen from Fig. 1, the VS1 trinistor is able to close the horizontal (according to the diagram) diagonal of the VD5 diode bridge. But this is tantamount to closing the vertical diagonal of the same bridge. Therefore, when the trinistor VS1 is open, the EL1 lamp is on; when it is not open, the lamp is extinguished.

Lamp EL1 and switch SA1 are standard electrical appliances available in the hallway. So, with the SA1 switch, you can still turn on the EL1 lamp at any time, regardless of the machine. You can turn it off only when the trinistor VS1 is closed.

However, it is also important that after closing the contacts of the SA1 switch, the machine will be de-energized. Therefore, the formation of the time delay can always be interrupted at will by closing and then opening the SA1 switch.

The machine is powered by a parametric stabilizer containing a ballast resistor R9, a rectifier diode VD4 and a zener diode VD2. This stabilizer produces a constant voltage of about 10 V, which is filtered by capacitors C6 and C5, and capacitor C6 smoothes out low-frequency ripples of this voltage, and C5 - high-frequency ones.

Briefly consider the operation of the machine (assuming that the SA1 switch is open). As long as the WA1 antenna is not blocked by the capacitance of the human body, there is a constant high level at the output of the DD2.1 element. Therefore, the single vibrator is in standby mode, in which the output of the DD2.2 element has a low level, locking (at the lower input of the DD2.4 element) the electronic key. As a result, the VS1 trinistor is not opened by the clock pulses arriving at the upper input of the DD2.4 element from the VD5 bridge through the R6 resistor.

When a person blocks the antenna circuit, a low level appears at the output of the DD2.1 element, triggering a single vibrator, and a high level appears at the output of the DD2.2 element, opening the electronic key and the trinistor VS20 for 1 s (the EL1 lamp is on during this time).

If by that time the blocking of the antenna circuit has been terminated (the person has left the mat), the EL1 lamp goes out, if not, it continues to burn until the person leaves the mat.

In any case, the single vibrator (and the machine as a whole) again goes into standby mode.

To turn off the light ahead of schedule (without waiting 20 seconds), if it is suddenly necessary, it is enough to close and open the SA1 switch. Then the machine also goes into standby mode.

The required sensitivity of the machine depends on the dimensions of the WA1 antenna, the thickness of the mat and other factors that are difficult to account for. Therefore, the desired sensitivity is selected by changing the resistance of the resistor R1. Thus, an increase in its resistance leads to an increase in sensitivity, and vice versa. However, one should not get carried away with excessive sensitivity for two reasons. First, an increase in the resistance of the resistor R1 above 1 MΩ, as a rule, requires filling it with varnish in order to exclude the influence of air humidity on the operating mode. Secondly, with excessive sensitivity of the machine, its false positives are not ruled out. They are also possible after the floor in the hallway is washed, but not yet dry. Then, in order to turn off the light, you should temporarily disconnect the WA1 antenna using a single-pole connector X1.

The WA1 antenna is a sheet of one-sided foil fiberglass, covered from the foil side with a second sheet of thin textolite, getinaks or polystyrene. Along the perimeter of the first sheet, the foil is removed in one way or another to a width of about 1 cm. Then both sheets are glued together, carefully filling with glue (for example, epoxy putty) those peripheral places of the antenna where the foil is removed.

Particular attention should be paid to the reliability of the termination of the wire coming from the foil to the outside of the antenna. Antenna dimensions vary by mat available. Approximately its area (on the foil) is 500 ... 1000 cm2 (suppose 20x30 cm). If the length of the wire going from the machine to the antenna is significant, it may need to be shielded (the screen stocking is connected to the lower terminal of the resistor R1). But then, on the one hand, the sensitivity of the automaton will inevitably decrease, on the other hand, the capacitance of the capacitor C1 may have to be increased somewhat.

Since the screen will be galvanically connected to the network, it must be covered with good and thick insulation on top.

The machine itself is assembled on a plastic board by printed or surface mounting. The board is placed in a plastic box of suitable dimensions, which prevents involuntary touching of any electrical point, since all of them are more or less dangerous, since they are connected to the network. For this reason, all soldering during adjustment should be carried out after disconnecting the machine from the mains (from the SA1 switch). The setting consists in choosing the sensitivity (with resistor R1), as already mentioned, and the shutter speed of the one-shot (with resistor R4), if necessary. By the way, the shutter speed can be increased to 1 min (at R4 = 820 kOhm) or more.

If you apply the details, as in Fig. 1, the maximum power of the EL1 lamp (or several lamps connected in parallel) can reach 130 W, which is quite enough for a hallway. Instead of the trinistor KU202N (VS1), it is permissible to install KU202M or, in extreme cases, KU202K, KU202L, KU201K or KU201L. Diode bridge (VD5) of the KTs402 or KTs405 series with the letter index Zh or I. If you use the bridge of the same series, but with the index A, B or C, the allowable power will be 220 watts. This bridge is easy to assemble from four individual diodes or two assemblies of the KD205 series. So, when using diodes KD105B, KD105V, KD105G, D226B, KD205E, you will have to limit the lamp power to 65 W, KD209V, KD205A, KD205B - ​​110 W, KD209A, KD209B 155 W, KD225V, KD225D - 375 W, KD202K, KD202L, KD202M, KD202N, KD202R, KD202S 440 W. Neither the trinistor nor the bridge diodes need a heat sink (radiator).

Diode VD1 - any pulse or high-frequency (germanium or silicon), and diodes VD3, VD4 - any rectifier, for example, series KD102-KD105. Zener diode VD2 - for a stabilization voltage of 9 ... 1O V, suppose, series KS191, KS196, KS210, KS211, D818 or type D814V, D814G. Transistor VT1 - any of the KT361, KT345, KT208, KT209, KT3107, GT321 series. Chips K561LA7 (DD1 and DD2) can be completely replaced by KM1561LA7, 564LA7 or K176LA7.

To improve heat dissipation, it is advisable to make a two-watt ballast resistor (R9) from four half-watt ones: with a resistance of 82 kOhm in parallel connection or a resistance of 5,1 kOhm in series connection. The remaining resistors are of the type MLT-0,125, OMLT-0,125 or VS-0,125. For electrical safety, the rated voltage of capacitor C2 (preferably mica) must be at least 500 V. Capacitors C1-C3, C5 and C7 are ceramic, mica or metal-paper with any rated voltage (except C2).

Oxide (electrolytic) capacitors C4 and C6 of any type with a rated voltage of at least 15 V.

Another version of the machine for turning on a table lamp (sconce, floor lamp or ceiling lamp) with a wave of the hand (light touch) is shown in Fig. 2. This machine, in essence, is an electronic analogue of a conventional push-button switch with a latch that works every other time: one press - the lamp is on, another - the lamp is off.

(click to enlarge)

This machine is also built on only two digital microcircuits, but instead of the second K561LA7 microcircuit (four logical elements 2I-NOT), it uses the K561TM2 microcircuit (two D-flip-flops). It is easy to see that the triggers of the last microcircuit are installed instead of the single vibrator of the previous machine. Let's briefly consider their work in the machine.

The purpose of the DD2.1 trigger is auxiliary: it provides a strictly rectangular shape of the pulses applied to the counting input C of the DD2.2 trigger. If there were no such pulse shaper, the DD2.2 flip-flop could not clearly switch at input C to a single state (when its direct output is high and its inverse output is low) or zero (when the output signals are opposite to those indicated) state. Since the installation input S (setting "one") of the trigger DD2.1 is constantly high relative to its installation input R (setting "zero"), its inverted output is a regular follower. That is why the integrating circuit R3C4 sharply sharpens the fronts of the pulses taken from the capacitor C3. When the voltage on it is low (the WA1 antenna is not affected by hand), the inverse output of the trigger DD2.1 also has a low voltage level. But as soon as the voltage on the capacitor C3 rises (bring your hand close enough to the WA1 antenna) to about 5 V, the low level at the inverse output of the trigger DD2.1 will change to a high one with a sharp jump.

On the contrary, after the voltage on the capacitor C3 decreases (the hand was removed) below 5 V, the high level at the same inverted output will also abruptly change to a low one. However, only the first (positive) of these two surges is important for us, since the DD2.2 trigger does not respond to a negative voltage surge (at input C). Therefore, the DD2.2 trigger will switch to a new state (single or zero) whenever the hand is brought to the WA1 antenna at a sufficiently close distance.

The direct output of the trigger DD2.2 is connected to the upper (according to the scheme) input of the element DD1.2, which is part of the electronic key. Acting on this input, the trigger is able to both open and close the electronic key, and with it the trinistor VS1, turning on or off thereby the EL1 lamp.

Note that the direct connection of the inverse output of the DD2.2 trigger with its own information input D ensures its operation in the desired counting mode - "every other time", but the integrating circuit C5R4 is needed so that after the power supply is applied to the machine (for example, after turning off the "plugs"), the DD2.2 trigger would be necessarily set to the zero state corresponding to the extinguished lamp EL1.

As in the previous machine, the EL1 lamp can also be turned on with a conventional SA1 switch. But it will be turned off if, on the one hand, the switch SA1 is open, on the other hand, the trigger DD2.2 is set to zero. Another feature of this machine is that the pulse generator (10 kHz) is assembled according to a simplified scheme - only two elements (DD1 and DD1.4) instead of three. Instead of the K561TM2 (DD2) microcircuit, it is permissible to use KM1561TM2, 564TM2 or K176TM2. Other details in it are the same as in the previous one. It makes sense to reduce the dimensions of the antenna to 50...100 cm2 over the area of ​​the foil.

Of undoubted interest for fans of tinkering is the simplest light machine (Fig. 3), containing only one microcircuit (DD1). This device is, as it were, an electronic analogue of a conventional button with a self-return: pressed - the lamp is on, released it went out. It is very convenient to provide such a contactless "button", for example, an easy chair, the light above which automatically lights up whenever you sit in it for reading, knitting or other outdoor activities.

(click to enlarge)

The difference between this simplified automaton and the previous ones is that it does not have a single vibrator or triggers. Therefore, the capacitor C3 is directly connected to the lower (according to the diagram) input of the DD1.2 element of the electronic key. If there is no “rider”, the WA1 antenna hidden under the seat upholstery does not prevent the occurrence of a pulse signal at the output of the DD1.1 element, the capacitor C3 is discharged, and therefore the electronic key and the trinistor VS1 are closed, the EL1 lamp is off. When a vacationer sits down in a chair, these pulses disappear, the capacitor C3 is charged and the electronic key allows the opening of the trinistor VS1, the light is on.

Of course, these examples are far from exhausting all the possibilities of using light automata.

Author: V.V.Bannikov

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