Infrared "electronic password" generator with encoder. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / infrared technology

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On fig. 45 shows a schematic diagram of an IR generator that generates a sequence of infrared flashes in a similar way.

Here DD1.1, DD1.2, Rl, ZQ1 is a master oscillator operating at a frequency of a clock quartz resonator ZQ1 - 32768 Hz. Microcircuits DD4 and DD5 make up an electronic switch, its output (combined outputs 3 DD4 and DD5) is connected to one of the X-inputs of these microcircuits, depending on the address received at the inputs 1, 2,4, and the signal at the input S (the microcircuit is activated with S=0). Address and signal S generates counter DD3. It is easy to calculate that the address change will occur here every 0,976 ms ((2 ^ 5) / 32768 s), this is tz - the duration of the familiarity in the code frame In the middle of each familiarity, a short (R4C2@10 μs) pulse at the output DD1.4. But this will happen only if this familiarity corresponds to a signal 1 at the output of the switch. This pulse will open a normally closed transistor amplifier (VT1, VT2, etc.) and the current generated in the IR diode BI1 will be converted into an IR flash of the same duration.

Rice. 45. IR "electronic password" generator (click to enlarge)

The generation of the code sequence begins (SA1 is on, the button SB1 is pressed) with the formation of a short pulse at the input R of the counter DD3 (tr@R3·C1), which sets it to its original, zero state, and ends with the appearance of a signal 1 at the output 29(vyIB. 14) DD3. The familiarity - there are obviously 16 of them - follow in time in accordance with the numbering (along the arrows) of the X-inputs of electronic switches: 1, 2, ..., 14, 15 (zero familiarity always corresponds to 1; this is the starting pulse of the package, not included, of course, among the code-forming ones). The total duration of the code message will thus be 0,976x15@14,6 ms.

The required number-code is formed by somehow switching the X-inputs of the microcircuits DD4, DD5: by connecting the i-th arrow to the "+" of the power source, if the i-th bit of the code should be 1 (X1 DD4, which forms the starting pulse of the package, is already connected to + Up, or to "ground" if it should be 0. So, for example, to generate the code 111011100111001, you will need to connect arrows 1, 2, 3, 5, 6, 7, 10, 11, 12, 15 with "+" , and the arrows 4, 8, 9,13, 14 - with the "-" of the power source.

Rice. 46. ​​Printed circuit board of the IR generator "electronic password"

Since n=15, the number of different signals, any of which can be switched as a code signal, is here 2^15=32768.

The generator is mounted on a printed circuit board made of double-sided foil fiberglass with a thickness of 1,2 ... 1,5 mm (Fig. 46). The foil on the side of the parts is used only as a common wire (a "-" power source is connected to it): in the places where the conductors pass, it should have samples - circles with a diameter of 1,5 ... 2 mm (not shown in the figure). The points of connection with the null foil of the "grounded" terminals of resistors, capacitors, etc. are shown in black squares; black squares with a light dot in the center - the "grounded" conclusions of the microcircuits and the position of the wire jumper connecting the "negative" conclusion of the capacitor C4 with the null foil.

As a power source for the generator, you can take a 6-volt battery 11 A (dimensions - Ж10,3x16 mm, electrical capacity - 33 mAh).

Switch SA1 type PD9-1 is mounted directly on the generator housing. The SB1 button, type PKN-159 or similar, must have a wire 6 ... 8 mm long, sufficient to lead it through the housing wall.

Rice. 47. Oscillogram of the code "111011100111001"

A properly assembled generator does not require adjustment. You can control its operation using an oscilloscope by connecting its input to the collector of the transistor VT1. After turning on SA1 and pressing the SB1 button on the oscilloscope screen (sweep waiting time 20 ... 30 ms), a sequence of pulses spaced in time in accordance with the switched signal should appear and disappear. If this is the code 111011100111001 discussed above, then the oscillogram shown in Fig. 47 ("extra" impulse, at the beginning of the package - starting). By the amplitude of the pulses measured across the resistor R9, one can judge the current in the IR diode Iimp@Uimp / R9 (Iimp - in amperes, Uimp - in volts, R9 - in Ohms), and in a fast sweep (20 ... 50 μs, also waiting) - about their shape and duration, which should be within 5 .. .15 µs.

The two-stage switching on of the code emitter - first with the SA1 switch, and then with the SB1 button - is associated with the peculiarity of self-excitation of quartz oscillators, with their rather slow (due to the high quality factor of the quartz resonator) entering the operating mode.

Rice. 48. Option to turn on the generator

Switch SA1 can be excluded by organizing the power supply of the generator as shown in fig. 48. But in this case, the SB1 button will need to be pressed twice: the first press will most likely give the wrong combination (which, by the way, can even be useful as masking the true code). The SA1 switch can also be dispensed with if a low-voltage battery of sufficient capacity is taken as a power source for the generator, capable of ensuring its continuous operation with constantly switched on microcircuits. For example, a lithium cell with EMF = 3 V, having an electric capacity of 0,1 Ah, can work in this mode for about a year.

Table 10

Upit, V	Ipot, µA	Iimp, A
2,4	5	0,18
3,7	16	0,38
4,3	30	0,38
5,0	60	0,46
6.0	140	0,59
7,0	360	0,72

Almost any IR diodes can be used in the code emitter, the restrictions are only overall: the height of the parts on the printed circuit board should not exceed 8 mm. All resistors here are of the MLT-0,125 type, non-electrolytic capacitors are KM-5, KM-6, K10-17B, etc. Capacitor C4 is of the K50-35 or K50-40 type. The operating voltage of the capacitor C6 (CE-DS Magsop, it is mounted in the "lying" position) must correspond to the voltage of the power source. In the variant shown in Fig. 48, it is necessary to first check the state of its dielectric: the leakage current in C6 must be less than 1 μA. By increasing the resistance of the resistor R9, which limits the current in the IR diode, the capacitance of the capacitor C6 can be reduced accordingly. A rather large "range" of the IR emitter (with R9 \u3,9d 10 Ohm exceeding XNUMX m) may simply be unnecessary.

The code generator remains operational in a wide range of supply voltages. Table 10 shows the dependence of the current Ipot consumed by it and the current in the IR diode Iimp on the power supply voltage Upit.

Publication: cxem.net

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