JPS59196624A - Ac two-wire type object detector - Google Patents

Abstract

PURPOSE:To attain small capacity by flowing most of currents only through a switching transistor (TR) at normal load in an AC 2-wire type object detector, turning off the currents at overload and flowing a small current to an SCR. CONSTITUTION:When an object approaches a detecting coil 12, the oscillation of an oscillating circuit 11 is stopped and when the object is parted, the oscillation is started, the oscillated output is detected by a TR21 and a capacitor 22, the output is fed to a gate of an SCR31 via TRs 23, 24 and a line 02 so as to turn on the SCR. A current flowing to the SCR31 turns on a TR45 via a diode 46, and when overload is caused, an excess current flows to the TR45, an SCR92 is turned on by the voltage increase of a resistor 91, the breakdown voltage of constant voltage diodes 46, 49 is set larger for the former diode, when the TR45 is turned off thereby protecting the TR45. Further, when an overcurrent flows to the load, the charging current of a capacitor 51 is increased, the TR23 is turned on, and no trigger signal is given to the SCR31 thereby cutting off the SCR.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a built-in sensor circuit and only two terminals, and has an AC power supply and a load connected between four terminals.
Connect in parallel, and depending on the detection operation of the pin 11 circuit, turn on between the two terminals as if it were a contact switch.
A-Fusukeru AC 2 Covers the Iti1 type object detection device.

A conventional AC two-wire object detection device is constructed as shown in FIG. 1, taking a proximity switch as an example. In this figure, the oscillation circuit 111i includes the LHE output coil 12.
When the object approaches the detection coil 12, the oscillation is stopped and the 11 oscillation is started. 1 to transistor 21 and capacitor 22 constitute a detection circuit that detects the oscillation output, and the detection output is ! - It is sent as a trigger signal to G1~ of 5CR31 through transistors 23 and 24. 5CR31 is a switching element for opening and closing the load, and is connected to terminals 71.7 via the die A-bridge 61.
Connected to 2. A constant voltage diode 32 and a current reading resistor 33 are connected in series to this 5CR 31, and further a rector-emitter path of a current limiting transistor 41 is connected in series. A resistor 4 for supplying base current is connected between the collector and base of this transistor 41.
2 are connected. SCR43 is for overcurrent detection.

The resistor 62 is used to supply current to the oscillation circuit 11 etc. when the SCR31 is off, and the diode 3 supplies the voltage generated at the anode of the constant voltage diode 32 to the oscillation circuit 11 etc. when the SCR31 is on. This is the one to add. An AC TI source 81 and loads such as a relay coil 82 are connected in series to the terminals 71 and 72.

If the object is not approaching the detection = 1 illumination 12, the oscillation circuit 11 is oscillating, and therefore the transistor 2
3 is on, 1-transistor 2/1 is off, and 5CR3
1 indicates that the LFD (light-emitting device A-F) 34 for displaying the result of the A state 'Qz% is not lit.

When an object approaches the detection coil 12, the oscillation is stopped, so that the 1 to 23 transistors are turned on, the 1 to 24 transistors are turned on, and the CR31 is turned on.
4, a current flows through it and it lights up, indicating that an object has been detected. At this moment, transistors 1 to 41 are supplied with base current through the resistor 42 and are turned on.

When 5CR31 is on, the relay coil 82 is on! 1
If an excessive 4R current flows due to a 10-circuit accident, etc.
The voltage across the current reading resistor 33 becomes high and the 5CR 43 turns on. In other words, the current flowing from 1 to the base of transistor 41 through resistor 42 now flows to 5CR43, turning off transistor 41 completely.Therefore, the current between the anode and cathode of 5CR31 becomes less than the holding current, and 5CR31 turns off. Become.

In the conventional circuit shown in FIG. 1, a 5CR31 is used as a switching element, and when this 5CR31 is turned on by a signal from the previous stage circuit, the current is 5C.
R31, constant voltage diode 32 and 1 helangister 4
1 in its series circuit. Therefore, when the load current is large, an SCR with a capacity corresponding to the load current is required, and consideration must be given to the temperature rise of the voltage regulator diode. On the other hand, the transistor needs to have a capacity that can withstand the overload event.For the reason 1-,
Semiconductor elements included in the switching circuit and the overload protection circuit become dolls, and it becomes difficult to make the proximity switch smaller and lower in price due to consideration of heat dissipation.

This Brahmei aims to improve the above-mentioned points and provide a compact and inexpensive AC two-wire object detection device. Nitotsu/j The explanation will be based on the examples. 1 to transistor 45. between the output terminals of the rectifier circuit 61. N flow detection 1 [(anti-9
1 (hereinafter referred to as resistor 91) is connected, and between this 1 and the base and collector of transistor 45 is 5O.
A series circuit consisting of R31, resistor 64, and constant voltage diode/I6 is connected. Constant voltage diode 46
The cathode of the resistor 65. One end of the series circuit consisting of the diode drawer 3 is connected, and the other end thereof is connected to the power supply terminal o1 of the preceding stage circuit including the sensor circuit. Goo 1~ of S CR92 is diode 971. Resistor 9 through resistor 95
1 connected to one end of the S A die A-de 93 is connected. The breakdown voltage of this constant voltage quad A-dead 93 has a value lower than the breakdown voltage of the constant voltage diode 46.

diode 34 connects the cathode of 5CR31 and SC
It is connected between the connection point of R92 with the anode and the negative terminal of the rectifier circuit 61, and one end of the resistor 62 is connected to the positive terminal of the rectifier circuit 61 through the resistor 66, and the other end is connected to the previous stage circuit. is connected to the power supply terminal 01 of. A connection point between the constant voltage diode 93 and the 5CR 92 is connected to a timer circuit made up of a capacitor 51 and a resistor 52 via a diode. This termer circuit output is I・Ranjisk 2
Applied to the base of 3.

Now, when a detection signal is sent from the previous stage circuit to the gate of 5CR31 with wire 02 in red, 5CR31 becomes A and 5CR3
The current flowing through 1 passes through the constant voltage diode 46 and causes the 1-transistor 45, which is a switching element, to become A. If the load in this state becomes overloaded due to a short circuit, etc.,
An excessive current flows through the transistors 1 to 45, and the voltage generated across the resistor 91 becomes high, so that 5CR92 becomes A. Now let the breakdown voltage of the voltage regulator diode 46.93 be Vz.
46. If expressed as Vz 93, as mentioned earlier, V
Since z 46 > Vz 93, the cathode of the constant voltage diode becomes lower than its breakdown voltage, and therefore the transistor 45 is turned off, so it is protected from overcurrent 73. At this time, the output from line 03 is The operation of the ζ timer circuit is performed.

Here, the operation of the timer circuit will be explained.

When the transistor 45 passes through the base, a voltage lower than the breakover voltage of the constant voltage dynode 93 is generated in the resistor 9G.
A thunderbolt emitted from both ends of the C is charged. The switches 1 to 23 are set to remain off. Next, when an overcurrent flows through the load, the voltage across the resistor 9G rises to the voltage of the constant voltage dynode 93, and rises from the charging potential of the capacitor 51 to the voltage of -LM. .1~Ran resistor 23 is 1 +
151 progresses), and as a result, transistors 1 to 24 are turned off. This state continues until the charge in the capacitor 51 is completely discharged, and 5CR3
No trigger signal is supplied to SCR31.
~ Cut off after the Riga Shin YJ is gone and maintain that state.

When the charge in content 1 bar 51 is completely discharged, transistors 1 to 23 are turned off again, and transistors 1 to 24 are turned off. Therefore, 5CR31 receives the trigger signal (and then
Become a person. Then, an excessive current flows again and the same operation as above is repeated, and this operation continues until the load reaches normal load (.

In the circuit shown in Figure 2, the large current flows through the transistor/
Since the base current of the transistor 45 flows through the 5CR 31, the constant current 11, and the diode A-46, a small capacitance is sufficient, and heat dissipation and the like need only be considered for the transistor 45. Note that after the transistor 45 is A, a diode 63 . Current flows through the resistor 65,
Although the current required by the oscillation circuit 11 and the like is about 10 mA at most, the current flowing through the 5CR31 is not large.

As explained above, according to the present invention, during normal load, most of the current flows through only the first switching means, so that the SCR and constant voltage are smaller in capacity than in the conventional example. A diode can be used, and the heat dissipation of the first switching means is better than the heat dissipation of a constant voltage diode. I'1: The design for heat dissipation becomes easy, and these factors combine to make it possible to realize a small and inexpensive AC two-wire object detection device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional example, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. . 11... Oscillation circuit 12... Detection = Iil 31.
...Load I? 5CR for l closing (second switching means) 33.91...Resistor for current detection 34...Light emitting diode for operation display 41...Transistor for current limitation 45...Transistor for load amount a1 <first (switching means) 92... 5CR for overcurrent detection (third switching means) 51... Capacitor for timer circuit 52... Resistor for timer circuit 61... Full wave rectifier circuit 71.72... Rectifier circuit input terminal 81...AC power supply 82...Load (relay) Patent applicant Tateishi Electric Co., Ltd.

Claims (1)

[Claims] (1) A terminal to which an alternating current and a load are connected in series, a rectifier circuit connected between these terminals, a sensor circuit to which power is supplied from the rectifier circuit, and a first sensor circuit connected to the rectifier circuit. A first series circuit including a switching means and a current detection resistor, a current limiting resistor connected between a control input terminal of the first switching means and one terminal of the rectifier circuit, and a second switching means. and a voltage regulator diode, and a power supply circuit connected between a connection point between the second switching means and the voltage regulator diode and the sensor circuit, The first switching means is turned on by passing η through the second switching means based on the signal of Based on the voltage, a current is supplied to the sensor circuit through the voltage supply circuit, and when the voltage 11 generated across the current detection resistor becomes large, the third switching cumulative voltage is activated. turns on and interrupts the supply current to the control input terminal of the first switching means! I'i J
, an AC two-wire type object detection device in which the first switching means is configured to be A/F.