JPH0589318A - Coin sensor - Google Patents

Abstract

PURPOSE:To obtain a coin sensor in which the both-terminal voltage of lower frequency between the both-terminal voltages of a receiving side coil does not become low, and detection precision at the time of detection by this lower frequency does not become low by making the impedance of a transmitting coil at the lowest frequency among the frequencies different from each other nearly equal to the output impedance of an amplifier. CONSTITUTION:A first oscillator 10 outputs the sine wave signal of 10kHz, and a second oscillator 20 outputs the sine wave signal of 160kHz, and a switching signal generator 30 generates a switching signal composed of the rectangular wave of 1kHz. The transmitting side coil 50 is a coil to flow the sine wave currents of 10kHz and 160kHz, and the impedance of the transmitting side coil 50 at 10kHz is set so as to be nearly equal to the output impedance of the amplifier 40. Besides, the kinds of the frequency of the sine wave current to flow in the transmitting side coil 50 can be three or more. Then, the receiving side coil 60 is opposed to the transmitting side coil 50 through a coil passage P, and receives a signal from the transmitting side coil 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coin sensor used for coin selection and the like.

[0002]

BACKGROUND ART A conventional coin sensor used for coin selection uses a coil installed on a wall of a coin passage, and when a coin approaches the coil, the inductance of the coil changes. A sine wave current is passed through the coil, and its frequency is about several kHz. However, when trying to sort coins in this way, aluminum (1 yen), brass (5 yen), copper (10 yen)
It is possible to select between coin series of yen) and bronze series (50 yen, 100 yen, 500 yen).
There is a drawback that you can't select among the bronze coins like 0 yen, 100 yen, 500 yen and 500 won.

To overcome this drawback, the Applicant has proposed a coin screening method which uses two signals of different frequencies. That is, the coil on the transmitting side and the coil on the receiving side are opposed to each other with the coin passage interposed therebetween, and a low-frequency current (for example, 10 kHz) and a high-frequency current (for example, 160 kHz) are alternately applied to the coil on the transmitting side to receive the coil on the receiving side. Both signals are received by the coil of and the lowest value of the low frequency voltage component,
The coins are sorted based on the lowest value of the high frequency voltage component. That is, if a coin exists between the coil on the transmitting side and the coil on the receiving side, an eddy current flows in the coin, which causes the electromagnetic field component generated on the transmitting side to be transmitted to the coil on the receiving side. Although the field component is attenuated, the amount of this attenuation varies from coin to coin, and even if two coins have the same amount of attenuation in a low frequency electromagnetic field, they have different amounts of attenuation in a high frequency electromagnetic field. Therefore, if two signals with different frequencies are used, the copper-based 500
It is possible to reliably select coins of almost the same shape such as yen coins and 500 won coins.

[0004]

By the way, when coins are selected by using two frequencies as described above, a sine wave signal of 160 kHz is amplified by a predetermined amplifier, and the amplified signal is amplified by 160 kHz. Flow into the transmission side coil, and a 10 kHz sine wave signal is amplified by an amplifier other than the above, and the amplified signal is 10 kHz.
It is sent to the z-side transmission coil and the above 2 is passed through the coin passage.
It is conceivable to provide two receiving coils facing each of the two transmitting coils.

However, this requires two amplifiers, two coils on the transmitting side, and two coils on the receiving side, which has the disadvantages of increasing the number of components and increasing the overall cost. Only one coil and one coil on the receiving side are provided, the signals of two frequencies are amplified by the amplifier, and the amplified signals are switched to sequentially
It is considered that the coins are sent to the transmitting side coil, the receiving side coil discriminates signals of two frequencies, and coins are sorted based on the signal received by the receiving side coil.

By the way, when the output impedance of the amplifier and the impedance of the transmitting coil are matched, the maximum electromagnetic field is supplied from the transmitting coil. On the other hand, when sorting coins of approximately the same material and approximately the same shape, such as when sorting 500-yen coins and 500-won coins, a higher frequency tends to facilitate sorting. Requires higher reception levels of high frequency signals, thereby increasing coin detection accuracy. Therefore, when matching the output impedance of the amplifier and the impedance of the transmitting coil, it is considered to set the impedance of the transmitting coil so that the impedance of the transmitting coil at a high frequency becomes equal to the output impedance of the amplifier. Be done.

[0007] However, in this case, of the voltage across the receiving side coil, the voltage across the low frequency becomes very low, and the detection accuracy when detecting at the low frequency becomes low. That is, since the voltage across the receiving coil is proportional to the frequency of the electromagnetic field interlinking therewith, when a 10 kHz signal and a 160 kHz signal are received, both ends of the receiving coil when a 10 kHz signal is received. The voltage is reduced to 1/16 of the voltage across the receiving coil when receiving a signal of 160 kHz. Therefore, of the voltage across the receiving coil, the voltage across the low frequency becomes extremely low, and there is a problem that the detection accuracy decreases when detecting at the low frequency.

An object of the present invention is to provide a coin sensor which does not lower the voltage across the low frequency among the voltage across the receiving coil and does not lower the detection accuracy when detecting at the low frequency. It is a thing.

[0009]

The present invention comprises at least two aspects.
A signal having two different frequencies is amplified by a predetermined amplifier, the amplified signal is sequentially flown to a transmitting side coil, and a receiving side coil is provided facing the transmitting side coil through a coin passage, and a receiving side coil is provided. A coin sensor for selecting coins passing through a coin passage based on a signal received by the coil, wherein the impedance of the transmitting coil at the lowest frequency among different frequencies is substantially equal to the output impedance of the amplifier. is there.

[0010]

According to the present invention, the impedance of the transmitting coil at the lowest frequency among the frequencies different from each other is substantially equal to the output impedance of the amplifier. Therefore, if the voltage at the low frequency is low among the voltage at the receiving coil. Therefore, the detection accuracy does not decrease when the detection is performed at the low frequency.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of an embodiment of the present invention.

In this figure, the first oscillator 10 is
The second oscillator 20 is a circuit that outputs a sine wave signal of kHz, the second oscillator 20 is a circuit that outputs a sine wave signal of 160 kHz, and the switching signal generator 30 generates a switching signal composed of a rectangular wave of 1 kHz. Circuit. The analog switches 11 and 21 are turned on according to the switching signal,
It is turned off to control passage of sine wave signals of 10 kHz and 160 kHz, respectively. In addition, the inverter 3
1 is for inverting the polarity of the switching signal. That is, when the switching signal output from the switching signal generator 30 is “High”, the analog switch 11
Is turned on to send a 10 kHz signal to the amplifier 40, and the analog switch 21 is turned off to prevent a 160 kHz signal from being sent to the amplifier 40, while the switching signal output from the switching signal generator 30 is "Low". , The analog switch 11 is turned off and 10 kHz
The signal is prevented from being sent to the amplifier 40, the analog switch 21 is turned on, and the 160 kHz signal is transmitted to the amplifier 40.
Sent to.

The capacitor 41 is provided between the amplifier 40 and the transmission side coil 50 and cuts a DC component.

The transmitting coil 50 has 10 kHz and 160 k
It is a coil that causes a sine wave current of 10 Hz to flow, and the impedance of the transmission side coil 50 at 10 kHz is equal to that of the amplifier 4
The output impedance is set equal to 0. The impedance of the transmitting coil 50 at 10 kHz does not need to be set to be exactly the same as the output impedance of the amplifier 40, and may be set to be substantially equal to the output impedance of the amplifier 40. The frequency of the sinusoidal current flowing through the transmitting coil 50 may be three or more. In that case, the impedance of the transmitting coil 50 at the lowest frequency among the different frequencies is the output impedance of the amplifier 40. It suffices if they are set to be approximately equal.

The receiving coil 60 is a coil that faces the transmitting coil 50 and receives a signal from the transmitting coil 50. The transmission side coil 50 and the reception side coil 60 are wound around a ferrite core via bobbins (not shown). A coin passage P is provided between the transmission side coil 50 and the reception side coil 60, and the coin C rolls in the coin passage P. The portion of the coin passage P located between the transmitting side coil 50 and the receiving side coil 60 is made of a material other than a conductor, for example, plastic.

The signal processing circuit 70 is a circuit for selecting the coin C passing through the coin passage P based on the signal received by the receiving side coil 60, and converts the signal received by the receiving side coil 60 into a digital signal. It has an A / D conversion circuit, a minimum value detecting means for obtaining the minimum value of the digital signal, and a table showing which coin the minimum value corresponds to. When the switching signal from the switching signal generator 30 is received by the signal processing circuit 70 and the switching signal is "High", it is determined that the signal of 10 kHz is received, and when the switching signal is "Low", 160 kHz. It is determined that the signal of is received. Further, although the minimum value detecting means is composed of a microprocessor, it may be composed of another discrete circuit.

Next, the operation of the above embodiment will be described.

First, the first oscillator 10 and the second oscillator 20 always operate to output sine wave signals of 10 kHz and 160 kHz, respectively, and the frequency of the switching signal is 1 kHz.
The width of the “High” is 0.5 msec, and the width of the “Low” is 0.5 msec. When the switching signal output from the switching signal generation circuit 30 is “High”, the analog switch 1
When 1 is opened and a 10 kHz sine wave signal is sent to the amplifier 40, the analog switch 21 is closed and a 160 kHz sine wave signal is not sent to the amplifier 40. When the switching signal output from the switching signal generation circuit 30 is “Low”, the signal is inverted by the inverter 31.
The analog switch 21 is opened to send a sine wave signal of 160 kHz to the amplifier 40, and the analog switch 11 is closed to send a sine wave signal of 10 kHz to the amplifier 40.
In this way, the transmission side coil 50 is alternately supplied with the sine wave signal of 10 kHz and the sine wave signal of 160 kHz.

By the way, the impedance of the transmitting coil 50 at 10 kHz is set to be equal to the output impedance of the amplifier 40. The output impedance of the amplifier 40 is set to 2.5Ω, so 10kH
The impedance of the transmitter coil 50 at z is also 2.5
Ω, and the inductance of the transmission coil 50 can be obtained from the equation of 2πfL = 2.5 (Ω). Note that π
Is about 3.14, f is 10 kHz, L is the inductance of the transmitting coil 50, and the transmitting coil 5
The resistance component of 0 is assumed to be 0 to simplify the explanation. Therefore, the inductance L of the transmitting coil 50
Is about 47 μH. In reality, since the resistance component of the transmission side coil 50 exists, the inductance of the transmission side coil 50 becomes larger than 47 μH depending on the resistance component.

In the above case, the impedance of the transmitting side coil 50 at 160 kHz is larger than 2.5Ω,
The output impedance of the amplifier 40 is not equal to 2.5Ω, and the impedance of the transmitter coil 50 at 160 kHz and the output impedance of the amplifier 40 are not impedance-matched. However, when compared with the signal component of 10 kHz, the signal component of 160 kHz has a capacitor 41.
Since the amount of attenuation at 1 is very small, there is no problem even if the impedance of the transmitter coil 50 and the output impedance of the amplifier 40 at 160 kHz do not match. Since the voltage across the receiving coil 60 is originally higher at 160 kHz than at 10 kHz, there is no problem even if the impedance of the transmitting coil 50 and the output impedance of the amplifier 40 at 160 kHz do not match.

Further, the signal processing circuit 7 in the above embodiment.
In 0, an A / D converter for converting the signal from the receiving coil 60 into a digital signal is provided. However, since the output level of the receiving coil 60 at a low frequency becomes high to some extent as described above, There is an advantage that an A / D converter having a small number of bits can be used.

The first oscillator 10, the second oscillator 20,
The frequency of the signal output by the switching signal generator 30 may be a value other than the above value, and the value of the output impedance of the amplifier 40 may be other than 2.5Ω.

FIG. 2 is a block diagram showing another embodiment of the present invention.

In the embodiment shown in FIG. 2, the capacitor 41 is removed from the embodiment shown in FIG. 1 and the transmission side coil 50 is directly connected to the output terminal of the amplifier 40. The same members as those in the embodiment shown in FIG. 1 are designated by the same reference numerals. Also in the embodiment shown in FIG. 2, the impedance of the transmitter coil 50 at the lowest frequency among the frequencies different from each other is set to be substantially equal to the output impedance of the amplifier 40.

In the embodiment shown in FIG. 1, the amplifier 40
A capacitor 41 is provided between the transmission side coil 50 and the transmission side coil 50. The capacitor 41 is for cutting the direct current component, and when the direct current component has already been reduced, the implementation shown in FIG. It is not necessary to provide the capacitor 41 as in the example, and even in such a case, the voltage across the low frequency does not become low among the voltage across the receiving coil, and the detection accuracy when detecting at that low frequency is low. It doesn't get lower.

[0026]

According to the present invention, of the voltage across the receiving coil, the voltage across the low frequency does not decrease, and the detection accuracy when detecting at the low frequency does not decrease.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

[Explanation of symbols]

 40 ... Amplifier, 41 ... Capacitor, 50 ... Transmitting coil, 60 ... Receiving side coil.

Claims (2)

[Claims] 1. At least two signals having mutually different frequencies are amplified by a predetermined amplifier, the amplified signals are sequentially flown to a coil on a transmission side, and the signals are received facing the transmission coil via a coin passage. A coin sensor provided with a side coil for selecting coins passing through the coin passage based on a signal received by the reception side coil, wherein the transmission side coil has the lowest frequency among the different frequencies. A coin sensor having an impedance substantially equal to the output impedance of the amplifier. 2. The transmission coil in a coin sensor according to claim 1, wherein the amplifier and the transmission coil are connected by a capacitor.