FR2791165A1 - METHOD FOR GENERATING ELECTROMECHANICAL RELAY SWITCHING NOISE - Google Patents

Abstract

To generate electromechanical relay switching noise on board a vehicle, an electro-acoustic transducer (4) is energized using an excitation circuit (1) producing a plurality of signals at various frequencies (131 -134) and the excitation circuit (1) is controlled to generate the various signals one after the other and at a sufficiently high rate so that each frequency returned by the transducer (4) is interrupted before it is becomes a note.

Description

-1 Method for generating relay switching noise

  electromechanical In a flashing central unit of a motor vehicle, a relay is beaten to cyclically supply the direction change lights.

We know two types of relays.

  On the one hand, there are electromechanical relays, consisting of a magnetic control coil of a movable contact blade. The driver, who activates the control unit, then perceives, in return, the beat noise, or switching, of the relay and can thus observe the effectiveness of its action and also verify that an automatic shutdown system of the control unit,

  controlled by the rotation of the steering wheel, does not act prematurely.

  On the other hand, power transistors tend to replace electromechanical relays because they are smaller and less expensive. These transistors are called static relays, since no moving part intervenes. As a result, the transistor does not produce, in a flashing unit, the acoustic feedback of electromechanical relay noise that the driver expects. We could think of recording a relay noise

  electromechanical to emit it through a loudspeaker provided for this purpose.

  However, such a solution would be expensive.

  The present invention aims to propose an economical solution for producing an electromechanical relay noise when a static relay switches. To this end, the invention relates to a method for generating an electromechanical relay switching noise on board a vehicle, characterized in that an electro-acoustic transducer is excited using an excitation circuit arranged to generate a plurality of signals at various frequencies and the excitation circuit is controlled to generate the various signals one after the other and at a rate sufficiently high that each frequency restored by the

  transducer is interrupted before it becomes a note.

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  A note being a musical sound at a frequency which characterizes it, it therefore takes a certain time for the note to be perceived to recognize its frequency. According to the method of the invention, each signal is interrupted before this perception time has elapsed. Thus, the actual switching noise of a relay, consisting of a whole spectrum of simultaneous frequencies, is here simulated by means of frequencies emitted successively and at a sufficiently high rate to prevent their individualization. It is therefore unnecessary to record the actual noise to be reproduced since simple frequencies, easy to generate, are sufficient to present, to the human ear, a noise which seems to be, to the latter, the

real relay noise.

  The invention will be better understood using the following description of a

  advantageous mode of implementing the method of the invention and variants, in a device for sound reproduction of an electromechanical relay switching noise, with reference to the appended drawing, in which: - Figure 1 is a block diagram of the playback device, and - Figure 2 shows the controls of a sound playback buzzer

relay noise.

  The device shown for sound reproduction of an electromechanical relay noise is used here to functionally supplement a flashing central unit with a static relay of a motor vehicle, to simulate the beat noise of an electromagnetic or mechanical relay when

the control unit works.

  The device comprises a microcontroller 1, shown limited by a dashed line frame, controlling a buzzer 4 through a series resistor 2 connected to the base of an NPN transistor 3 with emitter to ground. The buzzer 4 is connected between a 12 volt supply and the collector of the transistor 3, the buzzer 4 being, in this example, of the piezo type (capacitive). A resistor 5 is here provided, in parallel on the

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  buzzer 4, to reduce the impedance it presents and thus be able to

  order at a sufficient rate, by charging / discharging its capacity.

  The microcontroller 1, supplied with clock signals by a time base 10, comprises an input link 11 by which it is controlled by the central unit, and therefore by the user, to simulate the relay noise. It comprises a program memory 12, activated by the link 11, comprising a sequence of orders for selecting signals at various frequencies, or successive tones in a set 13 with no library memory containing digital signals representing a plurality of such frequencies, here at respective fundamental frequencies of 1, 2, 3 and 4 kHz, the signals representing them being respectively stored in four zones 131, 132, 133, 134 of the memory 13. For the sake of simplicity of the description, we limit ourselves here at four frequencies; in practice, it is preferable to have seven frequencies. One can then generate one of two noises, arming and disarming, relay by

  selection of a plurality of two signals at various frequencies.

  The two pluralities can differ from each other by the order in which the frequency signals are used and also by their size in number of frequencies. Thus, the "click" arming noise can be reproduced by means of five frequencies, while the "click" disarming or release noise requires seven frequencies. We can

  also use the same frequency several times.

  To simplify the rest of the description, it will be assumed that the memory 13 contains, for each tone or frequency, a digital pattern (FIG. 2) formed of a succession of identical blocks of bits in 1, blocks separated two by two by a space of bits at 0. This space comprises for example as many bits as a block, if one wishes to produce a signal at fundamental frequency of maximum power, that is to say without parasitic frequency other than the odd harmonics due to the pulse shape of the signals. Each pattern makes it possible to excite the buzzer 4 during here substantially T = two milliseconds, without exceeding about three milliseconds, by the blocks of bits forming binary pulse signals. This excitement of buzzer 4 in impulse form

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  represents percussions on this level and thus increases the

sound power.

  In FIG. 2, two sequences or patterns 24, 21 of bit blocks at two different frequencies have been shown, as a function of time t on the abscissa. The sequence 24 corresponds to blocks of one bit in 1 per period of two bits, providing 4 kHz, while the sequence 21 corresponds to blocks of four bits in 1 per period of eight bits, thus providing a signal at frequency 4 times lower, at 1 kHz,

  io when performing bit-by-bit reading at a fixed rate.

  To activate the buzzer 4, the software 12 selects the desired zone 131 to 134 in the library 13 and successively reads each of the bits. This reading takes place at a rate twice the frequency to be restored the highest in the library 13, that is to say here at 8 kHz. Given the duration of two

  patterns milliseconds, so each one has 16 bits here.

  In the example of FIG. 2, it is the area 134 of pattern 24 (4 kHz) which is first addressed, for the duration T of 2 ms. A multiplexer 14, with four channels connected to the respective areas 131 to 134, schematizes, in a very simplified manner, the selection of one of these by the program memory 12 which addresses the multiplexer 14, for transmitting the signals of the area 131 at 134 considered at the base of transistor 3. A demultiplexer or address decoder 135, for reading by line-to-line addressing of memory 13, is likewise controlled to scan the area 131 to 134 considered. In practice, the multiplexer 14 is integrated into the latter, and the program memory 12 successively addresses through the addressing circuit 135, at 8 kHz, the successive lines of the zone 131 to 134 desired. A data bus receives each bit read to temporarily store it in a flip-flop not shown controlling the base of the transistor 3. It can however be provided that the memory 13 directly controls the transistor 3, by a permanent link reserved for this purpose. Preferably, as here, the memory 12 programs a circuit 136 controlling the circuit 135 so that it selects the zone 131 to 134

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  desired and so that it reads it at the rate of an 8 kHz signal which it receives from the time base 10. The circuit 136 temporarily stores instructions from memory 12 and thus replaces the program in memory 12 for executing a routine task, of cyclic reading of a determined zone 131 to 134 relating to a tone. The circuit 136 here receives four clock signals, from time base 10, at 2, 4, 6 and 8 kHz and selects the latter, by an internal four-way multiplexer 137, to advance a line addressing counter (not shown)

  controlling the addressing circuit 135.

  The memory assembly 13 thus operates autonomously, in the manner of a coprocessor, during the period T of the control rhythm of the excitation circuits of the buzzer 4, which avoids overloading the

  general purpose circuits (computing unit and bus) of the microprocessor 1.

  Thus, the block 12 for executing instructions at the rhythm T is used, each time for a few machine cycles representing approximately ten microseconds, to program a frequency of the programmable frequency generator 13 and then the execution block 12 is released until 'to a new programming of the frequency generator 13 by

this one.

  In a variant, the blocks of the excitation bit pattern each have only one bit and there is only one pattern. To adjust the excitation frequency of the buzzer 4, the program memory 12 selects a scanning frequency for reading from the memory 13, scanning frequency which was fixed, at 8 kHz, in the previous example. The choice of the scanning frequency is stored in circuit 136 to activate the read addressing circuit 135 at the rate of output from the appropriate time base 10. To produce a value frequency determined at buzzer 4, you must read the single pattern with double frequency, in order to

  to transmit to each buzzer 4, a bit in 1 (first half

  period) then a bit in O (second half-period). Multiplexer 137 is then controlled by addressing its inputs to select the appropriate clock signal. For example, choosing 2 kHz for the adjustable sweep frequency will produce a pair of 1-bit readings in 1 and the

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  next bit at 0 every millisecond, so produce a signal

  acoustic at 1 kHz at the buzzer 4.

  In another variant, any excitation bit pattern in memory 13 has even been deleted and it has been replaced functionally by a switch or multiplexer such as 137 connecting, for the duration T, a clock output (here among four) from the time base 10 to the base of the transistor 3. This clock output is chosen from four which are, this time, directly those at the various frequencies capable of being selected, that is to say at 1 , 2, 3 and 4 kHz. The spatial pattern in memory 13 of the previous examples which was converted, by reading at known rhythm, into a temporal pattern, is thus here directly replaced by a

  time pattern provided by time base 10.

  Once the 2 ms period T has ended, the software in memory 12 then selects another zone 131-134, here zone 131, comprising signals at 1 kHz. This completion of period T is detected by an armed delay at the start of period T, or by the arrival of the line addressing counter mentioned above at an end of zone address 131-134, which causes an interruption of the microcontroller 1 It is thus possible to arm a timer at each frequency programming 13 and the generator frequency is deprogrammed when the timer expires. The jump to another tone or frequency in memory 13 is repeated at each expiration of period T and this for a total duration sufficient to produce the desired beat or switching noise, for example 10 to 30 ms, and this each time the central unit flashes the lights. Each jump to a new frequency also creates, at the level of the ear, a brutal transition which is very well perceived and is therefore equivalent to a sound emission which would be at a higher level. There is thus an audible signal of sufficient level to be clearly perceptible, which

  avoids the use of an amplifier.

  The various frequencies are chosen in an order such that their sequence simulates at best a beat noise, or successive clicks, of an electromechanical relay. Limitation of the buzzer 4 excitation time T by each frequency to a maximum value

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  determined prevents each frequency from becoming a noticeable note

by the human ear.

  Thus, to solve the problem posed at the beginning, we take into account the characteristics of the human ear, that is to say that we posed the problem differently from the classical approach. Indeed, the general problem is that the user perceives the noise he expects, and the conventional solution, consisting in emitting precisely this expected noise, is not in fact the only one. Indeed, as the user and also the sound reproduction transducer have a certain inertia and since, in addition, the actual noise of a switching is formed by a frequency spectrum, it is perfectly possible to simulate the actual noise by a rapid sequence of short signals of various frequencies, forming a kind of elementary percussion which, by the inertias mentioned above and the possible echoes, will appear to overlap. As the ear is only slightly sensitive to the relative delays between sounds, the rhythm of production of these frequencies does not produce a perceptible defect of restitution, even if the sequences between frequencies are not temporally spaced apart as it would be necessary to reproduce with precision the actual noise of a

switching.

  It is understood that the above method for generating a relay switching noise is independent of the function which the relay fulfills and that therefore it also finds application elsewhere than in a flashing unit. In addition, it can be used to sound only one change of state of a static relay with stable states, non-oscillating, for example powering up or cutting off the supply of an organ or electrical equipment. A static relay can moreover be an element other than a transistor in the strict sense and can for example be a

thyristor.

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Claims (9)

  1.- Method for generating an electromechanical relay switching noise on board a vehicle, characterized in that an electro-acoustic transducer (4) is excited using an excitation circuit (1) arranged to generate a plurality of signals at various frequencies (131-134) and the excitation circuit (1) is controlled to generate the various signals one after the other and at a rate (T) high enough that each frequency restored by the transducer (4) or   interrupted before it becomes a note.   2. A method according to claim 1, in which a   microcontroller (1) to excite the transducer (4).   3.- Method according to one of claims 1 and 2, wherein one excites the   transducer (4) by binary pulse signals.   4.- Method according to one of claims 2 and 3, wherein, the   microcontroller (1) comprising an instruction execution block (12) controlling a programmable frequency signal generator (13), the instruction execution block (12) is used at said rhythm (T), to program (136) a generator frequency (13), and then the execution block (12) is released until a new programming of the   frequency signal generator (13) therewith.   5.- Method according to claim 4, in which a timer is armed at each frequency programming and deprogrammed.   the frequency when the timer expires.   6.- Method according to one of claims 2 to 5, wherein   controls the transducer (4) by a time base (10) which   selects (137) one of several outputs at various frequencies.   7.- The method of claim 6, wherein the selected output is used to read, at adjustable speed, a single pattern of excitation bits in memory (13). 9 2791 165   8.- Method according to one of claims 1 to 7, wherein it generates   two noises, of arming and disarming, of relay by selection of a plurality of signals at various frequencies (131-134) among two pluralities of different lengths.   9.- Method according to one of claims 1 to 8, wherein the rhythm of   control of the excitation circuit (1) corresponds to a period of substantially two milliseconds.