EP1193656B1 - Switching circuit for generating a switch-on signal for battery-powered coin testers - Google Patents

Switching circuit for generating a switch-on signal for battery-powered coin testers Download PDF

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Publication number
EP1193656B1
EP1193656B1 EP01250342A EP01250342A EP1193656B1 EP 1193656 B1 EP1193656 B1 EP 1193656B1 EP 01250342 A EP01250342 A EP 01250342A EP 01250342 A EP01250342 A EP 01250342A EP 1193656 B1 EP1193656 B1 EP 1193656B1
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EP
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Prior art keywords
oscillator
switching circuit
switching
coin
switching element
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EP01250342A
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German (de)
French (fr)
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EP1193656A3 (en
EP1193656A2 (en
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Bernd Rothe
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Walter Hanke Mechanische Werkstaetten GmbH and Co KG
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Walter Hanke Mechanische Werkstaetten GmbH and Co KG
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    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D5/00—Testing specially adapted to determine the identity or genuineness of coins, e.g. for segregating coins which are unacceptable or alien to a currency
    • G07D5/08—Testing the magnetic or electric properties

Definitions

  • the invention relates to a circuit arrangement for generating a switch-on signal for battery-operated coin validator according to the preamble of the main claim.
  • an electrical turn-on sensor for battery operated coin validators that uses an oscillator is known.
  • a first connected to the oscillator transistor in emitter follower circuit, a first dischargeable via a first capacitor capacitor is periodically charged so that the first transistor is de-energized when reducing the oscillator voltage.
  • a second battery voltage lying transistor is driven, which generates a turn-on signal.
  • the oscillator voltage breaks down when a coin is inserted into the coin validator while attenuating the coil of the oscillator.
  • the GB 2011 086 A1 describes a proximity detector for detecting metal objects with an oscillator and a driving circuit connected to the oscillator via an amplifier.
  • the driver circuit outputs an output signal when the amplitude of the oscillator's AC signal falls to zero or below a predetermined threshold, due to the presence of a metal object.
  • the invention has for its object to provide a circuit arrangement for generating a switch-on signal according to the preamble of the main claim, which always ensures a stable operating point and in which all component tolerances are compensated.
  • the single FIGURE shows a circuit-specific embodiment of the circuit arrangement according to the invention.
  • the circuit arrangement shown in the figure is used to switch on a battery-operated electronic coin validator, wherein electronic circuits of the coin validator, such as electronic testing devices are supplied with voltage by means of a switch-on signal generated by the circuit arrangement.
  • An essential requirement of the circuit arrangement shown is that it has a low power consumption in the stationary state and also in the operating state.
  • the circuit arrangement consists essentially of a Colpitts oscillator 1, a first circuit 2 for adjusting the operating point of the oscillator 1 in the stationary state of Münzprüers, a second circuit 3 for driving a first electronic switching element Q4, which represents the output of the circuit arrangement and throwing a coin gives a turn-on signal for the electronic circuits of the coin validator.
  • the Colpitts oscillator 1 consists in a known manner of a capacitive voltage divider C3, C4, which determines the fraction of the coupled voltage.
  • the series connection of the capacitors C3, C4 acts as a resonant circuit capacitance.
  • the coil L1 of the Colpitts oscillator is connected to the terminals of the capacitors C3, C4 and their inductance together with the capacitors C3, C4 determines the resonant frequency.
  • the Colpitts oscillator has two MOS field-effect transistors Q3, Q5, whose drain electrodes are connected to each other and form the output of the oscillator 1, whose gate electrodes are common to the live terminal of the capacitor C3 and their source electrodes on the one hand a resistor R2 to the battery voltage U Batt and on the other hand via a resistor R6 to ground or GND, are connected. Parallel to the resistor R6, a capacitor C2 is connected, which ensures that the negative feedback for the AC voltage (R6) goes to zero.
  • the substrate of the field effect transistor Q3 is connected to battery voltage, while the substrate of the field effect transistor Q5 is grounded.
  • the resistors R2 and R6 preferably have the same resistance and also the FETs Q3, Q5 are identical.
  • the Colpitts oscillator is designed so that the current consumption does not exceed 10 ⁇ A.
  • the power consumption is essentially determined by the quiescent current flowing through the transistors Q3 and Q5.
  • the two resistors R2 and R6 and the switching thresholds of the transistors Q3 and Q5 are decisive for the quiescent current.
  • I U B ⁇ a ⁇ t ⁇ t - U Q ⁇ 3 .
  • Q ⁇ 5 / R ⁇ 2 + R ⁇ 6 12 ⁇ V - 5 ⁇ V / 1 . 36 M ⁇ O ⁇ H ⁇ m ⁇ 5 . 14 ⁇ ⁇ A
  • the circuit for adjusting the operating point of the oscillator 1 in the stationary state of Münzprüers has a transistor Q1, which is designed as a PNP transistor on.
  • the emitter of the transistor Q1 is connected to battery voltage while the collector is connected to the source of the FET Q3.
  • the base of the transistor Q1 as a control electrode is on the one hand via a capacitor C1 to the battery voltage and on the other hand via a resistor R3, which serves to adjust the base current, connected to a resistor R1, wherein the resistor R1 with its other terminal is also at battery voltage.
  • the resistance value of R1 is much larger than that of R3.
  • the second circuit 3 for driving the electronic switching element Q4 has a diode D1, preferably a Schottky diode whose anode is connected to the output of the oscillator 1 and whose cathode is connected to the gate terminal of a MOS-FETs Q2.
  • Parallel to the diode D1 is a resistor R4.
  • the source of the FET Q2 is connected to the junction between resistor R3 and resistor R1 of the first circuit 2, and the drain is connected both to a resistor R5 and to the gate of the electronic switching element Q4 also implemented as a MOSFET connected.
  • the other terminal of the resistor R5 is grounded.
  • the substrate of the MOS-FET Q2 is connected to the battery voltage.
  • the source of the FET Q4 forms the output for the turn-on signal and the drain and the substrate are grounded.
  • the operation of the circuit arrangement shown in the figure is as follows.
  • the operating point of the oscillator 1 is centered on the operating voltage, ie battery voltage and results from the two same resistors R2 and R6.
  • the oscillator supplies at its output with the DC voltage U Batt / 2 superimposed AC voltage, which is rectified via the diode D1, whereby at the gate electrode of the subsequent MOS transistor Q2 is a DC potential of about U Batt / 2 plus U ⁇ peak , Since this DC voltage is well below the operating voltage, the MOS transistor Q2 is conductive, whereby a voltage drop across the resistor R1 and the resistor R5 occurs.
  • the capacitor C1 charges and as soon as its voltage has reached the switching threshold of the transistor Q1, the latter becomes conductive.
  • the operating point of the oscillator 1 is adjusted, i. E. the operating point is shifted towards the battery voltage.
  • This also shifts the output voltage of the oscillator 1, i. the amplitude remains the same, but the center voltage is shifted, increasing the DC potential at the gate of MOS transistor Q2.
  • the MOS transistor Q2 partially shuts off, i. the drain-source resistance changes and thus the voltage drop across R1 decreases until a voltage value of approximately 500 mV has been established at the resistor R1, which corresponds to the emitter base voltage of the transistor Q1.
  • the MOS-FET Q2 now operates as a constant-current source, wherein the current through the resistor R1, the MOS-FET Q2 and the resistor R5 by R1 or by the emitter-base voltage of the transistor Q1 is determined.
  • the resistor R5 is dimensioned so that the voltage drop across the resistor R5 does not exceed the switching threshold of the MOS transistor Q4.
  • the circuits 2 and 3 operate as a regulator, which ensures that the current through R1 and R5 remains constant.
  • the state thus set is the resting state of the circuit arrangement, i. the coin validator is waiting and awaiting the insertion of a coin.
  • the circuit arrangement ensures a stable operating point in this state, whereby all component tolerances are balanced.
  • the oscillation of the oscillator 1 is attenuated, whereby the amplitude of the AC voltage is smaller.
  • the diode blocks LD1 and no longer conducts, whereby the capacitance of the gate electrode of the MOS-FET Q2 discharges via the resistor R4.
  • the decreasing gate voltage generates a higher current through transistor Q2 and thus a higher voltage drop across resistor R5.
  • the switching threshold of the transistor Q4 is exceeded, whereby the transistor Q4 switches to GND or ground and produces an output signal, ie a turn-on signal for the electronic circuits of the coin validator.
  • the circuit parameters of the circuit arrangement are dimensioned such that the voltage change at the transistor Q2 occurs relatively quickly. This is necessary for capacitor C1 to hold the voltage for transistor Q1 and not discharge.
  • the capacitor C1 thus prevents that the operating point of the oscillator 1 adjusts via the transistor Q1, ie by the capacitor C1, a spontaneous readjustment is prevented, since otherwise no output signal from the transistor Q4 would be generated.
  • the oscillator After inserting the coin, the oscillator again takes its stable operating point and the MOS transistor Q2 acts again as a constant current source.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
  • Testing Of Coins (AREA)
  • Dc-Dc Converters (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Transmitters (AREA)
  • Keying Circuit Devices (AREA)
  • Electronic Switches (AREA)

Abstract

The circuit has an oscillator with a detection coil and a first switch element that outputs the control signal when the coin is inserted. A first stage sets the oscillator working point in the rest state. A second stage has a switch element that acts as a constant current source in the rest state. Its current changes when a coin is inserted depending on oscillator output voltage so the first switch element switches and outputs a switch-on signal. The circuit has an oscillator (1) with a coil for detection coin insertion whose output signal is changed by the coin and a first electronic switch element (Q4) that outputs the control signal when the coin is inserted by changing its control voltage. A first stage (2) sets the oscillator working point in the rest state. A second stage (3) connected to the oscillator output has a second electronic switch element (Q2) and is connected to the first stage so that the second switch element acts as a constant current source in the rest state. The current in the switch element changes when a coin is inserted depending on the oscillator output voltage so that the first switch element switches and delivers the switch-on signal.

Description

Die Erfindung betrifft eine Schaltungsanordnung zur Erzeugung eines Einschaltsignals für batteriebetriebene Münzprüfer nach dem Oberbegriff des Hauptanspruchs.The invention relates to a circuit arrangement for generating a switch-on signal for battery-operated coin validator according to the preamble of the main claim.

Aus der EP 0 607 624 B1 ist ein elektrischer Einschaltsensor für batteriebetriebene Münzprüfer bekannt, der einen Oszillator verwendet. Über einen ersten, an den Oszillator angeschlossenen Transistor in Emitterfolgeschaltung wird ein erster über einen ersten Widerstand entladbarer Kondensator periodisch so aufgeladen, daß der erste Transistor bei Verringerung der Oszillatorspannung stromlos wird. Über den ersten Transistor wird ein zweiter an Batteriespannung liegender Transistor angesteuert, der ein Einschaltsignal erzeugt. Die Oszillatorspannung bricht zusammen, wenn eine Münze in den Münzprüfer eingeworfen wird und dabei die Spule des Oszillator gedämpft wird.From the EP 0 607 624 B1 For example, an electrical turn-on sensor for battery operated coin validators that uses an oscillator is known. A first, connected to the oscillator transistor in emitter follower circuit, a first dischargeable via a first capacitor capacitor is periodically charged so that the first transistor is de-energized when reducing the oscillator voltage. About the first transistor, a second battery voltage lying transistor is driven, which generates a turn-on signal. The oscillator voltage breaks down when a coin is inserted into the coin validator while attenuating the coil of the oscillator.

Die GB 2011 086 A1 beschreibt einen Näherungsdetektor zum Detektieren von Metallgegenständen mit einem Oszillator und einem über einen Verstärker mit dem Oszillator verbundenen Treiberkreis. Der Treiberkreis gibt ein Ausgangssignal ab, wenn die Amplitude des Wechselsignals des Oszillators durch das Vorhandensein eines Metallgegenstandes auf Null bzw. unter eine vorgegebene Schwelle fällt.The GB 2011 086 A1 describes a proximity detector for detecting metal objects with an oscillator and a driving circuit connected to the oscillator via an amplifier. The driver circuit outputs an output signal when the amplitude of the oscillator's AC signal falls to zero or below a predetermined threshold, due to the presence of a metal object.

Der Erfindung liegt die Aufgabe zugrunde, eine Schaltungsanordnung zur Erzeugung eines Einschaltsignals entsprechend dem Oberbegriff des Hauptanspruchs zu schaffen, die immer einen stabilen Arbeitspunkt gewährleistet und bei der alle Bauelementetoleranzen ausgeglichen werden.The invention has for its object to provide a circuit arrangement for generating a switch-on signal according to the preamble of the main claim, which always ensures a stable operating point and in which all component tolerances are compensated.

Diese Aufgabe wird erfindungsgemäß durch die kennzeichnenden Merkmale des Hauptanspruchs gelöst.This object is achieved by the characterizing features of the main claim.

Einerseits wird durch die besondere Ausbildung des Colpitts-Transistors ein niedriger Stromverbrauch gewährleistet und das Vorsehen der Konstantstromquelle ergibt einen stabilen Arbeitspunkt über den gesamten Temperaturbereich einen Ausgleich der Bauteiletoleranzen und einen Ausgleich von ungewollter Beeinflussung durch Metallgegenstände im Münzprüfer. Weiterhin wird durch die Konstantstromquelle ein stabiler Schaltpunkt für den Ausgangstransistor geliefert, wodurch die Wirkung von Schwankungen der Schaltschwellen der verwendeten integrierten Schaltkreise, die zwischen 30% und 50% liegen, unterdrückt werden.On the one hand, a low power consumption is ensured by the special design of the Colpitts transistor and the provision of the constant current source results in a stable operating point over the entire temperature range compensation of component tolerances and compensation for unwanted influence by metal objects in Münzprüfer. Furthermore, a stable switching point for the output transistor is supplied by the constant current source, whereby the effect of fluctuations in the switching thresholds of the integrated circuits used, which are between 30% and 50%, are suppressed.

Durch die in den Unteransprüchen angegebenen Maßnahmen sind vorteilhafte Weiterbildungen und Verbesserungen möglich.The measures specified in the dependent claims are advantageous developments and improvements possible.

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und wird in der nachfolgenden Beschreibung näher erläutert.An embodiment of the invention is illustrated in the drawing and will be explained in more detail in the following description.

Die einzige Figur zeigt eine schaltungsgemäße Ausgestaltung der erfindungsgemäßen Schaltungsanordnung.The single FIGURE shows a circuit-specific embodiment of the circuit arrangement according to the invention.

Die in der Figur dargestellte Schaltungsanordnung dient zum Einschalten eines batteriebetriebenen elektronischen Münzprüfers, wobei mittels eines von der Schaltungsanordnung erzeugten Einschaltsignals elektronische Schaltkreise des Münzprüfers, wie elektronische Prüfeinrichtungen mit Spannung versorgt werden. Eine wesentliche Anforderung an die dargestellte Schaltungsanordnung besteht darin, daß sie im ruhenden Zustand und auch im Betriebszustand einen geringen Strombedarf aufweist.The circuit arrangement shown in the figure is used to switch on a battery-operated electronic coin validator, wherein electronic circuits of the coin validator, such as electronic testing devices are supplied with voltage by means of a switch-on signal generated by the circuit arrangement. An essential requirement of the circuit arrangement shown is that it has a low power consumption in the stationary state and also in the operating state.

Die Schaltungsanordnung besteht im Wesentlichen aus einem Colpitts-Oszillator 1, einem ersten Schaltkreis 2 zum Einstellen des Arbeitspunktes des Oszillators 1 im ruhenden Zustand des Münzprüfers, einem zweiten Schaltkreis 3 zum Ansteuern eines ersten elektronischen Schaltelementes Q4, das den Ausgang der Schaltungsanordnung darstellt und bei Einwurf einer Münze ein Einschaltsignal für die elektronischen Kreise des Münzprüfers abgibt.The circuit arrangement consists essentially of a Colpitts oscillator 1, a first circuit 2 for adjusting the operating point of the oscillator 1 in the stationary state of Münzprüers, a second circuit 3 for driving a first electronic switching element Q4, which represents the output of the circuit arrangement and throwing a coin gives a turn-on signal for the electronic circuits of the coin validator.

Der Colpitts-Oszillator 1 besteht in bekannter Weise aus einem kapazitiven Spannungsteiler C3, C4, der den Bruchteil der mitgekoppelten Spannung bestimmt. Dabei wirkt die Reihenschaltung der Kondensatoren C3, C4 als Schwingkreiskapazität. Die Spule L1 des Colpitts-Oszillators ist mit den Anschlüssen der Kondensatoren C3, C4 verbunden und ihre Induktivität bestimmt zusammen mit den Kondensatoren C3, C4 die Resonanzfrequenz. Weiterhin weist der Colpitts-Oszillator zwei MOS-Feldeffekttransistoren Q3, Q5 auf, deren Drain-Elektroden miteinander verbunden sind und den Ausgang des Oszillators 1 bilden, deren Gate-Elektroden gemeinsam an dem spannungsführenden Anschluß des Kondensators C3 liegen und deren Source-Elektroden einerseits über einen Widerstand R2 an die Batteriespannung UBatt und andererseits über einen Widerstand R6 an Masse oder GND, angeschlossen sind. Parallel zum Widerstand R6 ist ein Kondensator C2 geschaltet, der dafür sorgt, daß die Gegenkopplung für die Wechselspannung (R6) gegen Null geht. Das Substrat des Feldeffekttransistors Q3 liegt an Batteriespannung, während das Substrat des Feldeffekttransistors Q5 auf Masse liegt. Die Widerstände R2 und R6 haben vorzugsweise den gleichen Widerstandswert und auch die FETS Q3, Q5 sind identisch.The Colpitts oscillator 1 consists in a known manner of a capacitive voltage divider C3, C4, which determines the fraction of the coupled voltage. In this case, the series connection of the capacitors C3, C4 acts as a resonant circuit capacitance. The coil L1 of the Colpitts oscillator is connected to the terminals of the capacitors C3, C4 and their inductance together with the capacitors C3, C4 determines the resonant frequency. Furthermore, the Colpitts oscillator has two MOS field-effect transistors Q3, Q5, whose drain electrodes are connected to each other and form the output of the oscillator 1, whose gate electrodes are common to the live terminal of the capacitor C3 and their source electrodes on the one hand a resistor R2 to the battery voltage U Batt and on the other hand via a resistor R6 to ground or GND, are connected. Parallel to the resistor R6, a capacitor C2 is connected, which ensures that the negative feedback for the AC voltage (R6) goes to zero. The substrate of the field effect transistor Q3 is connected to battery voltage, while the substrate of the field effect transistor Q5 is grounded. The resistors R2 and R6 preferably have the same resistance and also the FETs Q3, Q5 are identical.

Der Colpitts-Oszillator ist so ausgelegt, daß die Stromaufnahme 10 uA nicht überschreitet. Der Stromverbrauch wird im wesentlichen durch den Ruhestrom, der durch die Transistoren Q3 und Q5 fließt, bestimmt. Bestimmend für den Ruhestrom sind die beiden Widerstände R2 und R6 sowie die Schaltschwellen der Transistoren Q3 und Q5. Es ergibt sich z.B. folgende Rechnung: I = U B ⁢ a ⁢ t ⁢ t - U Q ⁢ 3 , Q ⁢ 5 / R ⁢ 2 + R ⁢ 6 = 12 ⁢ V - 5 ⁢ V / 1 , 36 M ⁢ O ⁢ h ⁢ m ∼ 5 , 14 μ ⁢ A

Figure imgb0001
The Colpitts oscillator is designed so that the current consumption does not exceed 10 μA. The power consumption is essentially determined by the quiescent current flowing through the transistors Q3 and Q5. The two resistors R2 and R6 and the switching thresholds of the transistors Q3 and Q5 are decisive for the quiescent current. For example, the following calculation results: I = U B ⁢ a ⁢ t ⁢ t - U Q ⁢ 3 . Q ⁢ 5 / R ⁢ 2 + R ⁢ 6 = 12 ⁢ V - 5 ⁢ V / 1 . 36 M ⁢ O ⁢ H ⁢ m ~ 5 . 14 μ ⁢ A
Figure imgb0001

Der Schaltkreis zum Einstellen des Arbeitspunktes des Oszillators 1 im ruhenden Zustand des Münzprüfers weist einen Transistor Q1, der als pnp-Transistor ausgebildet ist, auf. Der Emitter des Transistors Q1 ist an Batteriespannung angeschlossen, während der Kollektor mit dem Sourceanschluß des FETs Q3 verbunden ist. Die Basis des Transistors Q1 als Steuerelektrode liegt einerseits über einen Kondensator C1 an der Batteriespannung und ist andererseits über einen Widerstand R3, der zur Einstellung des Basisstroms dient, mit einem Widerstand R1 verbunden, wobei der Widerstand R1 mit seinem anderen Anschluß gleichfalls an Batteriespannung liegt. Dabei ist der Widerstandswert von R1 sehr viel größer als der von R3.The circuit for adjusting the operating point of the oscillator 1 in the stationary state of Münzprüers has a transistor Q1, which is designed as a PNP transistor on. The emitter of the transistor Q1 is connected to battery voltage while the collector is connected to the source of the FET Q3. The base of the transistor Q1 as a control electrode is on the one hand via a capacitor C1 to the battery voltage and on the other hand via a resistor R3, which serves to adjust the base current, connected to a resistor R1, wherein the resistor R1 with its other terminal is also at battery voltage. The resistance value of R1 is much larger than that of R3.

Der zweite Schaltkreis 3 zum Ansteuern des elektronischen Schaltelementes Q4 weist eine Diode D1, vorzugsweise eine Schottky-Diode auf, deren Anode mit dem Ausgang des Oszillators 1 und deren Kathode mit dem Gate-Anschluß eines MOS-FETs Q2 verbunden ist. Parallel zur Diode D1 liegt ein Widerstand R4. Die Source-Elektrode des FETs Q2 ist mit dem Verbindungspunkt zwischen Widerstand R3 und Widerstand R1 des ersten Schaltkreises 2 verbunden und die Drain-Elektrode ist sowohl an einen Widerstand R5 als auch an den Gate-Anschluß des gleichfalls als MOS-FET ausgebildeten elektronischen Schaltelementes Q4 angeschlossen. Der andere Anschluß des Widerstandes R5 liegt auf Masse. Das Substrat des MOS-FETs Q2 ist an die Batteriespannung angeschlossen. Die Source-Elektrode des FETs Q4 bildet den Ausgang für das Einschaltsignal und die Drain-Elektrode sowie das Substrat liegen auf Masse.The second circuit 3 for driving the electronic switching element Q4 has a diode D1, preferably a Schottky diode whose anode is connected to the output of the oscillator 1 and whose cathode is connected to the gate terminal of a MOS-FETs Q2. Parallel to the diode D1 is a resistor R4. The source of the FET Q2 is connected to the junction between resistor R3 and resistor R1 of the first circuit 2, and the drain is connected both to a resistor R5 and to the gate of the electronic switching element Q4 also implemented as a MOSFET connected. The other terminal of the resistor R5 is grounded. The substrate of the MOS-FET Q2 is connected to the battery voltage. The source of the FET Q4 forms the output for the turn-on signal and the drain and the substrate are grounded.

Die Funktionsweise der in der Figur dargestellten Schaltungsanordnung ist wie folgt. Wenn die Schaltungsanordnung an Spannung, d.h. an Batteriespannung gelegt wird, liegt der Arbeitspunkt des Oszillators 1 mittig zur Betriebsspannung, d.h. Batteriespannung und ergibt sich aus den beiden gleichen Widerständen R2 und R6. Der Oszillator liefert an seinem Ausgang eine mit der Gleichspannung UBatt/2 überlagerte Wechselspannung, die über die Diode D1 gleichgerichtet wird, wodurch an der Gate-Elektrode des nachfolgenden MOS-Transistors Q2 ein Gleichspannungspotential von etwa UBatt/2 plus U~Spitze liegt. Da diese Gleichspannung deutlich unter der Betriebsspannung liegt, wird der MOS-Transistor Q2 leitend, wodurch ein Spannungsabfall über den Widerstand R1 und über den Widerstand R5 auftritt.The operation of the circuit arrangement shown in the figure is as follows. When the circuit is connected to voltage, ie to battery voltage, the operating point of the oscillator 1 is centered on the operating voltage, ie battery voltage and results from the two same resistors R2 and R6. The oscillator supplies at its output with the DC voltage U Batt / 2 superimposed AC voltage, which is rectified via the diode D1, whereby at the gate electrode of the subsequent MOS transistor Q2 is a DC potential of about U Batt / 2 plus U ~ peak , Since this DC voltage is well below the operating voltage, the MOS transistor Q2 is conductive, whereby a voltage drop across the resistor R1 and the resistor R5 occurs.

Dadurch lädt sich der Kondensator C1 auf und sobald seine Spannung die Schaltschwelle des Transistors Q1 erreicht hat, wird letzterer leitend. Dadurch wird der Arbeitspunkt des Oszillators 1 verstellt, d.h. der Arbeitspunkt wird zur Batteriespannung hin verschoben. Dadurch verschiebt sich auch die Ausgangsspannung des Oszillators 1, d.h. die Amplitude bleibt gleich, aber die Mittenspannung wird verschoben, wodurch das Gleichspannungspotential am Gate des MOS-Transistors Q2 ansteigt. Mit steigender Gate-Spannung sperrt der MOS-Transistor Q2 teilweise, d.h. der Drain Source Widerstand ändert sich und damit nimmt auch der Spannungsabfall über R1 ab, bis sich ein Spannungswert von ca. 500 mV am Widerstand R1 eingestellt hat, der der Emitter-Basisspannung des Transistors Q1 entspricht. Der MOS-FET Q2 arbeitet jetzt als Konstant-Stromquelle, wobei der Strom über den Widerstand R1, den MOS-FET Q2 und den Widerstand R5 durch R1 bzw. durch die Emitter-Basisspannung des Transistors Q1 bestimmt wird. Dabei ist der Widerstand R5 so dimensioniert, daß der Spannungsabfall an den Widerstand R5 die Schaltschwelle des MOS-Transistors Q4 nicht überschreitet. Die Schaltungen 2 und 3 arbeiten als Regler, der dafür sorgt, daß der Strom durch R1 und R5 konstant bleibt.As a result, the capacitor C1 charges and as soon as its voltage has reached the switching threshold of the transistor Q1, the latter becomes conductive. As a result, the operating point of the oscillator 1 is adjusted, i. E. the operating point is shifted towards the battery voltage. This also shifts the output voltage of the oscillator 1, i. the amplitude remains the same, but the center voltage is shifted, increasing the DC potential at the gate of MOS transistor Q2. As the gate voltage increases, the MOS transistor Q2 partially shuts off, i. the drain-source resistance changes and thus the voltage drop across R1 decreases until a voltage value of approximately 500 mV has been established at the resistor R1, which corresponds to the emitter base voltage of the transistor Q1. The MOS-FET Q2 now operates as a constant-current source, wherein the current through the resistor R1, the MOS-FET Q2 and the resistor R5 by R1 or by the emitter-base voltage of the transistor Q1 is determined. In this case, the resistor R5 is dimensioned so that the voltage drop across the resistor R5 does not exceed the switching threshold of the MOS transistor Q4. The circuits 2 and 3 operate as a regulator, which ensures that the current through R1 and R5 remains constant.

Der so eingestellte Zustand ist der Ruhezustand der Schaltungsanordnung, d.h. der Münzprüfer ist im Wartezustand und wartet auf den Einwurf einer Münze. Durch die Schaltungsanordnung wird ein stabiler Arbeitspunkt in diesem Zustand gewährleistet, wobei alle Bauelementetoleranzen ausgeglichen sind.The state thus set is the resting state of the circuit arrangement, i. the coin validator is waiting and awaiting the insertion of a coin. The circuit arrangement ensures a stable operating point in this state, whereby all component tolerances are balanced.

Wird nun ein Metallgegenstand in die Nähe der Spule L1 des Oszillators 1 gebracht, d.h. wird eine Münze eingeworfen, so wird die Schwingung des Oszillators 1 gedämpft, wodurch die Amplitude der Wechselspannung kleiner wird. Dadurch sperrt die Diode LD1 und leitet nicht mehr, wodurch die Kapazität der Gate-Elektrode des MOS-FETs Q2 sich über den Widerstand R4 entlädt. Die kleiner werdende Gatespannung erzeugt einen höheren Strom durch den Transistor Q2 und somit einen höheren Spannungsabfall am Widerstand R5. Dadurch wird die Schaltschwelle des Transistors Q4 überschritten, wodurch der Transistor Q4 nach GND oder Masse schaltet und ein Ausgangssignal, d.h. ein Einschaltsignal für die elektronischen Schaltkreise des Münzprüfers erzeugt. Die Schaltungsparameter der Schaltungsanordnung sind dabei so bemessen, daß die Spannungsänderung am Transistor Q2 relativ schnell auftritt. Dies ist notwendig, damit der Kondensator C1 die Spannung für den Transistor Q1 hält und sich nicht entlädt. Der Kondensator C1 verhindert somit, daß sich der Arbeitspunkt des Oszillators 1 über den Transistor Q1 nachstellt, d.h. durch den Kondensator C1 wird eine spontane Nachregelung verhindert, da ansonsten kein Ausgangssignal vom Transistor Q4 erzeugt würde.If now a metal object is brought into the vicinity of the coil L1 of the oscillator 1, that is, a coin dropped, the oscillation of the oscillator 1 is attenuated, whereby the amplitude of the AC voltage is smaller. As a result, the diode blocks LD1 and no longer conducts, whereby the capacitance of the gate electrode of the MOS-FET Q2 discharges via the resistor R4. The decreasing gate voltage generates a higher current through transistor Q2 and thus a higher voltage drop across resistor R5. As a result, the switching threshold of the transistor Q4 is exceeded, whereby the transistor Q4 switches to GND or ground and produces an output signal, ie a turn-on signal for the electronic circuits of the coin validator. The circuit parameters of the circuit arrangement are dimensioned such that the voltage change at the transistor Q2 occurs relatively quickly. This is necessary for capacitor C1 to hold the voltage for transistor Q1 and not discharge. The capacitor C1 thus prevents that the operating point of the oscillator 1 adjusts via the transistor Q1, ie by the capacitor C1, a spontaneous readjustment is prevented, since otherwise no output signal from the transistor Q4 would be generated.

Nach dem Einwurf der Münze nimmt der Oszillator wiederum seinen stabilen Arbeitspunkt ein und der MOS-Transistor Q2 wirkt wieder als Konstant-Stromquelle.After inserting the coin, the oscillator again takes its stable operating point and the MOS transistor Q2 acts again as a constant current source.

Claims (9)

  1. Switching circuit for generating a switch-on signal for battery-powered coin testers, with an oscillator comprising a coil for recording the insertion of a coin, the output signal of which is changed by the coin, and with a first electronic switching element, the same transmitting the switch-on signal when a coin is inserted by changing its control voltage, characterised in that a first switching circuit (2) is envisaged for adjusting the working point of the oscillator (1) in a resting condition of the coin tester, and a second switching circuit (3) comprising a second electronic switching element (Q2) for controlling the first switching element (Q4), whereby the control electrode of the second switching element (Q2) is connected with the output of the oscillator (1) via a diode (D1), the same supplying a direct voltage overlaying an alternating voltage as the output voltage, and whereby the first switching circuit (2) comprises a transistor (Q1), via which the working point adjustment of the oscillator (1) for the resting position of the coin tester can be activated, whereby the control electrode of the transistor (Q1) comprises a parallel switching of a condenser (C1) connected to the battery voltage and a resistor (R1), and is connected with a point in the switching path of the second switching element (Q2), whereby the first switching circuit (2) the working point of the oscillator adjusts the coin tester in a resting position in such a way that the second switching element (Q2) acts as a constant current source supplying a constant current, with which the switching threshold of the first electronic switching element (Q4) is not reached, and that the current through the second switching element (Q2) changes depending on the output voltage of the oscillator (1) in such a way when a coin is inserted that the first switching element (Q4) connected with second switching element (Q2) switches and supplies the switch-on signal.
  2. Switching circuit according to Claim 1, characterised in that the diode (D1) is sized in such a way that the same locks when the output voltage of the oscillator (1) changes due to the presence of a coin.
  3. Switching circuit according to Claim 1 or 2, characterised in that the battery voltage is applied for activating the working point adjustment, whereby the output voltage of the oscillator (1) controls the second switching element (Q2) via the diode (D1) in such a way that the same becomes conductive, so that the condenser (C2) connected with the second switching element (Q2) is charged, and switches the transistor (Q1) of the first switching circuit (2) to become conductive.
  4. Switching circuit according to one of the Claims 1 to 3, characterised in that the working point of the oscillator (1) lies central to the battery voltage when the first switching circuit (2) is not activated, and is displaced by half the battery voltage when the first switching circuit (2) is activated.
  5. Switching circuit according to one of the Claims 1 to 4, characterised in that a resistor (R5) positioned on the switching threshold of the first switching element (Q4) is switched in series with the switching path of the second switching element (Q2).
  6. Switching circuit according to one of the Claims 1 to 5, characterised in that the first and/or second switching element (Q2, Q4) takes the form of a field effect transistor, preferably an MOS field effect transistor.
  7. Switching circuit according to one of the Claims 1 to 6, characterised in that the oscillator is a Colpitts oscillator.
  8. Switching circuit according to one of the Claims 1 to 7, characterised in that a resistor (R4) is switched parallel with the diode (D1), via which the capacity of the control electrode of the second switching element (Q2) can be discharged when the diode (D1) is locked.
  9. Switching circuit according to one of the Claims 1 to 8, characterised in that the condenser (C1) of the first switching circuit (1) is sized in such a way that an adjustment of the working point of the oscillator (1) is prevented for a certain period of time when a coin is inserted and a voltage change occurs at the second switching element (Q2).
EP01250342A 2000-09-29 2001-09-27 Switching circuit for generating a switch-on signal for battery-powered coin testers Expired - Lifetime EP1193656B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10049758 2000-09-29
DE10049758A DE10049758B4 (en) 2000-09-29 2000-09-29 Circuit arrangement for generating a switch-on signal for battery-operated coin validators

Publications (3)

Publication Number Publication Date
EP1193656A2 EP1193656A2 (en) 2002-04-03
EP1193656A3 EP1193656A3 (en) 2005-02-02
EP1193656B1 true EP1193656B1 (en) 2007-12-12

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ID=7659030

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Application Number Title Priority Date Filing Date
EP01250342A Expired - Lifetime EP1193656B1 (en) 2000-09-29 2001-09-27 Switching circuit for generating a switch-on signal for battery-powered coin testers

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EP (1) EP1193656B1 (en)
AT (1) ATE381147T1 (en)
DE (2) DE10049758B4 (en)
ES (1) ES2296704T3 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100967367B1 (en) 2006-09-01 2010-07-05 리서치 인 모션 리미티드 Integrated dialing

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3581105A (en) * 1968-09-23 1971-05-25 Bell & Howell Co Switching apparatus
US4105105A (en) * 1975-10-17 1978-08-08 Libandor Trading Corporation Inc. Method for checking coins and coin checking apparatus for the performance of the aforesaid method
GB2011086A (en) * 1977-10-13 1979-07-04 Skf Uk Ltd Improvements in or relating to inductive proximity detectors
CH676147A5 (en) * 1988-06-17 1990-12-14 Vibro Meter Ag
EP0399242B1 (en) * 1989-05-19 1996-03-20 Festo KG Temperature stabilized inductive proximity switch
DE4301530C1 (en) * 1993-01-21 1994-06-30 Nat Rejectors Gmbh Inductive switch-on sensor for battery operated coin validators
CH690950A5 (en) * 1996-06-13 2001-02-28 Optosys Ag Temperature-stabilized oscillator, and using the same in a proximity switch.

Also Published As

Publication number Publication date
ATE381147T1 (en) 2007-12-15
DE50113361D1 (en) 2008-01-24
EP1193656A3 (en) 2005-02-02
DE10049758B4 (en) 2004-07-22
ES2296704T3 (en) 2008-05-01
EP1193656A2 (en) 2002-04-03
DE10049758A1 (en) 2002-04-18

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