Detecting plate for an identification system

Start of patent duration: I960 10 15 © Dependence:

AT 362 425

Pamphlets considered to delineate the prior art:

AT-PS 295895 US-PS 3299424

- 2 No. 362425

The invention relates to a Detektierplättchen for an electronic identification system, comprising a receiving stage, a counter controlled by the receiving stage, one of these subordinate coding circuit for generating platelet-specific pulse packets, as well as with a

Rectifier arrangement for the recovery of a supply voltage from an externally fed signal.

Such identification systems may be used, for example, where certain rooms of a building are to be accessible only to a predetermined group of persons, or in the automatic transport and / or registration of goods. Persons, goods or animals carry a Detektierplättchen in which there is an electronic circuit that emits a signal due to an electromagnetic field generated in the detection zone, or affects the strength of the electromagnetic field, which in turn can be detected again.

If such systems are used in which a signal is generated by the detector wafer and emitted again, a receiver stage is provided in addition to a transmitter group which receives the re-transmitted signal and further processes it into a detection signal. If, on the other hand, the detector wafer influences the electromagnetic field generated, then only one transmission stage is required for this electromagnetic field and a circuit coupled to the transmission stage detects the changed load of the transmission stage caused by the detector wafer and processes it into a detection signal.

The electronic circuit contained in the detection plates for an identification system encodes the detection signal with a code which is assigned to the respective detection plate and thus to the person, product or animal carrying it.

In practice, such an identification system, for example, in a run stall for cows apply. There are several feeders in the playpen that are accessible to all cows in a herd. However, for proper treatment of cows, it is necessary for each cow to receive a feed mix adapted to that cow in a measured amount. This can be accomplished by providing each cow with a coded detection wafer and providing a detection zone at each manger. In this way, the cow located in front of a manger can be identified and it can be adjusted feed amount and feed mixture of the cow in question.

For example, a detector pad for an electronic identification system is the subject of U.S. Patent No. 3,299,424. This known detector wafer contains a resonant circuit which is detuned periodically in accordance with a code, to which the detector wafer also contains a detuning switch stage and a code generator. For the switch stage and the code generator, however, a separate power source in the form of a battery is required. The use of batteries in detector plates, however, has great disadvantages because batteries must be replaced after a certain time; Moreover, in batteries, just before they exhaust themselves, the terminal voltage drops slightly, which can lead to incorrect coding and incorrect identification.

From AT-PS no. 295,895 a Detektierplättchen of the aforementioned type is known. For the transmission of the feedback signals of the detecting detector plate to an evaluation circuit containing identifiers in this known system, the usual receiver-transmitter chain is provided with a separate receiving stage and transmitter stage. However, this means a considerable circuitry outlay, so that these known platelets come into question only in limited numbers for special operations.

The invention is therefore based on the task of minimizing the circuitry complexity so much that when ensuring the coding of Identifikandensignals a small plate is created, which is accessible for use in large quantities.

According to the invention, this is achieved in the known platelets defined above in that the output of the coding circuit is fed back to the receiving circuit designed as a resonant circuit via a feedback stage and that the coding circuit is formed as a clocked coding circuit, so that the resonant circuit is tuned for predetermined periods of time, wherein preferably the rectifier arrangement is connected directly to the resonant circuit.

- 3 No. 362425

As a result, the receiving level can also be used as a transmission stage, u.zw. for a given by the predetermined periods of time period. By this means is for a separate

Transmission stage required circuitry overhead avoided.

It has proven to be particularly advantageous if the rectifier arrangement is connected directly to the resonant circuit, since by that means a not further compactness of the

Platelet can be achieved.

The invention will now be described by way of example with reference to the drawings. 1 shows schematically an embodiment of a detector wafer according to the invention; FIG. 2 shows the circuit diagram of an electronic identification system for a detection wafer according to the invention, and FIG. 3 shows some signal forms occurring during operation of the circuit according to FIG.

Fig.l shows a Detektierplättchen -W-, in which there is a resonant circuit consisting of a coil -L- and a capacitor -C-, whose resonant frequency corresponds to the frequency of a prevailing in a Detektierzone electromagnetic detection field. If that

Detecting plate is brought into the detection zone, therefore, the LC circuit is caused to resonate by the detection field. This creates an alternating voltage across the LC circuit, of which in this example the coil and the capacitor are connected in parallel.

About diodes -D₂ and D₂And capacitors -C₂ and C₂- This AC voltage is converted into a DC supply voltage and designed as an integrated circuit

Counting and coding circuit -TC- supplied. The AC voltage generated across the LC circuit is further supplied via a resistor -R- to the counting input of the circuit -TC-. The peaks of the AC voltage can be used as shunting pulses for the counting part of the circuit -TC-.

A counter with n levels has 2ⁿ possible output combinations. A simple counter with

10 stages therefore already has 1024 different initial states. With the aid of the coding part of the circuit -TC-, a code signal -CS- can now be formed which is characteristic of a specific detector wafer or a specific group of detector plates and which coincides with one of the possible output states of the counter. This characteristic signal -CS- is used to periodically detune or even short the resonant circuit with a rhythm determined by the coding part of the circuit -TC-.

The detuning of the resonant circuit can be effected by periodically connecting an additional capacitor in parallel to the capacitor C- or periodically short-circuiting a portion of the coil L. It is also possible to use the code signal -CS- to periodically pick up a nonlinear element in the circuit or to modulate an oscillator signal.

If a detection wafer of the type described is now in a detection field, a periodic detuning occurs, with a rhythm determined by the circuit -TC-, resulting in a periodic weakening of the signal re-transmitted by the detection wafer, which can easily be detected, or but a change in the energy absorption by the detector wafer, which can also be detected. The specific rhythm of weakening or absorption variation allows the identification of persons, goods or animals.

Fig. 2 shows in more detail an electrical circuit arrangement for a detector according to the invention. The circuit arrangement comprises, as indicated in Fig.l, a Re45 resonant circuit, consisting of a parallel circuit of a coil -L- and a capacitor -C-. Next are again rectifier organs -D₂ and D₂And capacitors -C, and C₂- Provided that form a supply circuit and supply a supply voltage when the resonant circuit is in resonance. The supply circuit further comprises a capacitor -C_r -, And a Zener diode -Z- to limit the voltage to a predetermined value.

In deviation from the circuit arrangement shown in Fig.l is in the circuit arrangement of Figure 2 is a separate oscillator -O₂ - Recorded, which oscillates as soon as the voltage supplied by the resonant circuit reaches a suitable value. The oscillator -0₂- Is built in a known manner on two NAND gates, acting as an integrated circuit

- 4 No. 362425 are commercially available, and some resistors and capacitors. An advantage of using the separate oscillator -O_a-, which provides the counts for a digital counter -T-, is that the frequency of the oscillator is very stable and is not dependent on external disturbances. The pulses of the oscillator are applied to the digital counter -T-, which is designed as an integrated circuit and receives the supply voltage from the resonant circuit. The counter -T- has five outputs -Α, B, C, D and E-, which are connected in the illustrated embodiment with two integrated, commercial, digital multiplexer circuits -20 and 21-. The circuits -20 and 21- have a number of control inputs -Sal, Sbl, Sei and Sei, and Sa2, Sb2, Sc2 and Se2-, respectively. Furthermore, the multiplexer circuits each have a number of code inputs -CI1 and CI2-. The signals offered to the control inputs determine which coding inputs are connected to the output terminals -Ul or U2 connected. The predetermined number of coding inputs determines the number of possible codings. The number of possible codings could therefore be increased by still using a third multiplexer circuit.

FIG. 3 shows a number of signal forms occurring in the circuit arrangement according to FIG. With Α, B and C are the signals that occur at the corresponding outputs of the counter -T-, and the inputs -Sal, Sbl, Sei or Sal, Sb2 and Sc2- the multiplexer circuits are supplied. With D and E output signals of the counter are also indicated. These signals fulfill a special task. The signal D is not supplied to a control input but to a coding input of the multiplexer circuits. This causes only during certain time intervals, in this case, when the signal D has a low logic level, a coded signal is transmitted.

The signal E is fed directly to the input -Sei- the first multiplexer circuit and inverted via a NAND gate -22- at the input -Se2- the second multiplexer circuit. In this way, it is caused that when the signal E has a high logic level, the first multiplexer circuit -20- outputs a code signal, and that when the signal E has a low logic level, the second multiplexer circuit -21- outputs a code signal ,

The output signals of the multiplexer circuits -20 and 21- are supplied to a switch via a NAND gate -23- connected as an inverter. The switch consists essentially of a transistor -25-, which can be brought into the conductive or in the locked state by means of the code signals. An example of a signal applied via a series resistor and a shunt capacitor to the base of the transistor is indicated at F in FIG. With

I and II, the intervals are given, in which the coding of the multiplexer circuit -20 or 21- originates.

With the aid of the signal F, the base of the transistor -25- is controlled. When the transistor is in the conductive state, the resonant circuit LC- is short-circuited in this embodiment, so that here the resonant circuit is extremely detuned. The signal formed by the resonant circuit is shown at G in FIG.

Since the resonant circuit not only forms a coded signal but also supplies the supply voltage for the coding means, the resonant circuit can not remain short-circuited for too long. This is the reason for the above-described processing of the signal D, which causes the resonant circuit to not be short-circuited at least 50% of the time, so that so-called energy transfer blocks are formed in the signal G. These energy transfer blocks -30- may be further used to generate a sync signal on the detection side of the system, which may be on both the transmit side and a separate receive side of the system. The synchronizing signal can be converted into a clock signal which, in synchronism with the code signal, introduces the code signal into a shift register.

For the signal transmission between the Detektierplättchen and a decoding device, in addition to the periodic short-circuiting of the entire resonant circuit, there are other possibilities.

Nr.362425

For example, with the aid of the switch -25-, an additional coil or an additional capacitor can be switched into the resonant circuit, or decoupled just by a short circuit of the resonant circuit. Further, it is possible to periodically switch a non-linear element, such as a diode, into the resonant circuit by means of the switch. In the former case, the resonant circuit is detuned in a coded manner; in the latter case, the resonant circuit encoded forms at least a third frequency when starting from two transmission frequencies.

The detection wafer described can be used both in an identification system with a transmitting device serving as a receiving device at the same time as in an identification system with a transmitting device and a receiving device.

Various modifications of the described detector wafer are obvious to the person skilled in the art. It is essential that the Detektplülchen generates its own counts, from which a code is formed, consisting of energy transfer blocks and code blocks, the energy transfer blocks are used to recover a synchronized signal on the detection side, for example by means of a phase loop circuit. As a result, a coding which is almost insensitive to interference is obtained in the detection wafer, while detection of the code on the detection side can take place in a reliable manner.