DE3014192A1 - Status signal to indicate overload condition - uses oscillator gated to drive display and alarm if overload occurs - Google Patents

Abstract

A status monitoring facility for use with electronic control systems provides indication of any danger level caused by a short circuit or overload condition. The system uses an oscillator (7) that has tuned frequency to drive a light emitting diode (12). At the same time a buzzer may be activated as an additional alarm. If a short circuit occurs on the coupled load a voltage drop occurs (13,14) to switch a bistable (4) that in turn causes transistors (1,9,17) to switch of the load unit. A further bistable (5) switches and the buzzer (6) is activated and at the same time the oscillator (7) is gated to activate the diode (12) at the tuned frequency.

Description

Signaling device

The invention relates to a signaling device according to the preamble of claim 1.

In electronic controls, especially in programmable logic Controls that are used in industrial plants are included in the considerations Basically assumed for safety only such electronic equipment to use that, without suffering damage, with non-electronic equipment can be combined because specially at the interfaces to the peripheral Consumers face particular problems. This is z. B. then be the case if a short circuit or an overcurrent occurs at the consumers being controlled which leads to the destruction of the electronic equipment. To the To protect electronic equipment, the outputs of the electronic Controls are very often short-circuit proof. One speaks here of an electronic Fuse that enables the electronic Exit without replacing individual parts or other measures without restriction will be functional again. Furthermore, the controls mentioned so-called status displays by means of luminescent diodes are almost always provided for each output, which light up when an output is instructed.

With the multitude of exits and the ever increasing working speed of the electronic controls, it is very difficult to detect a defect in the ones to be controlled Detect solenoid valves, contactors or the like early enough. By a short circuit or overcurrent would destroy the electronic output without causing the failure Under certain circumstances is noticed immediately, which can lead to considerable consequential damage.

In order to achieve security in this regard, it is the task of Invention to prevent destruction of outputs and a short circuit that has occurred or to display overcurrent by changing the function of the existing status display.

This signaling device for each output of the electronic Control with the existing luminescent diodes marked as status display is made possible by the status display of the relevant output in the event of a short circuit from the instruction, for example a central processing unit of a programmable logic unit Control separated and for this to an oscillator with a certain frequency is switched.

Since the frequency of the oscillator is clearly higher than that occurring at the output Switching frequency, an existing short circuit is acted upon by the flashing frequency Immediately recognizing the luminescent diode, especially since a buzzer or another at the same time acoustic signal with continuous tone is activated.

Further explanations of the invention are given below with reference to the Circuit diagram given. It should be noted that here only an output of a larger number of outputs of an electronic controller is shown and is described. In order to be able to recognize the function better, the undisturbed operation and then the disrupted operation is explained.

Undisturbed operation: The switching voltage that is required for the Action of the consumer (V) connected to (K) is required. Is at (U2) the required supply voltage for the operation of the downstream electronic Assemblies such as B. the two bistable flip-flops (4,5) and the frequency-determining one Oscillator (7).

A coming from the electronic control and applied to (ES) defined signal in the order of magnitude of (U2) caused by the base resistance (8) the switching through of the transistor (9), which has been blocked until then. About the collector emitter -Route (C-E) of the transistor (9) and via the base resistor (10) is the connection of the transistor (1) completed and the consumer (V) switched on. Here is takes into account that with the resistor (2) and the emitter-base path (E-B) of the Transistor (1) due to the inherent losses between the connection points (13,14) a voltage drop is recorded, which in the case of undisturbed operation for the downstream evaluation circuit (3) has no consequences. Simultaneously with switching through of the transistor (9) is via its collector-emitter path (C-E) and the downstream Diode (11) the luminescent diode (12) for the duration of the set signal (ES) switched. This luminescent diode (12) thus shows the undisturbed operation the output of the electronic control and its status.

Disturbed operation: A disrupted operation occurs when the switched consumer (V) a short circuit occurs.

The short-circuit current occurring during a short circuit causes an between the connection points (13,14) measurable voltage drop, which is significantly greater than with undisturbed operation.

This much higher voltage drop has the response of the evaluation circuit (3) result in which the flip-flop (4) switches to the other stable state.

The flip-flop (4) in turn switches via the resistor (16) Transistor (17), what to block the transistor (9) and thus to immediate shutdown of the consumer (V) leads via the transistor (1). Furthermore, the Tilt stage (4), the tilt stage (5) switched. This leads to the activation of the buzzer (6) and the connection of the oscillator (7), the oscillator (7) via the Diode (15) acts on the luminescent diode (12). The luminescent diode (12) becomes like this on and off with the frequency of the oscillator.

According to the mode of operation recorded up to this point, it should be noted that that the short circuit that occurred at the consumer (V) to block the output led that the buzzer (6) was put into action, and that for the undisturbed Operation used luminescent diode (12), which is normally used in electronic controls is intended as a status display, now with a flashing frequency indicates the short circuit at the consumer (V) of the output concerned. The luminescent diode (12) thus serves as a status display and at the same time as a display for the disturbed Operation.

Now it goes to the blocked output, which is caused by a short circuit was caused to fix.

To do this, press the button (R) in the path (18).

The impulse given with the button (R) shifts the toggle stages (4,5) in their original state. The buzzer (6) is switched off. The tilting stage (4) is switched back immediately due to the pending short circuit, so that the Luminiszenzdiode- (12) with said flashing frequency the not yet resolved Short circuit continues to show. The tilting stage (5), however, remains in the reset position Location, since their recovery time is certain to be longer than the recovery time the tilting stage (4) lies. The output remains blocked until the short circuit is actually fixed. Only after the short circuit has been eliminated is the button (R) reset the multivibrator (4), whereby the transistors (1,9) in their initial state can be moved and an undisturbed operation can be continued.

Claims (2)

Claims signaling device for electronic controls, which both the status of a switched consumer and the short circuit of the Displays consumer, characterized in that a) for the status display and for the short-circuit display only a luminescent diode (12) is used as Short circuit display compared to the status display the short circuit with a certain Flashing frequency. b) a short-circuit current occurs in the event of a short circuit at the consumer (V), that between the connection points (13, 14) compared to the undisturbed operation causes a voltage drop, which causes the evaluation circuit (3) to respond Has consequence, whereby the flip-flop (4) switched to the other stable state is, c) the flip-flop (4) in turn via the resistor (16) the transistor (17) switches what to block the transistor (9) and thus to immediate shutdown of the consumer (V) leads via the transistor (1), d) the flip-flop (4) the oscillator (7) and the toggle stage (5) switches, which activates the buzzer (6) is, e) the oscillator (7) via the diode (15) the luminescent diode (12) with the Frequency of the oscillator (7) switched on and off, f) when you press the in the path (19) lying button (R) the flip-flops (4,5) in their original states be moved, which switches off the buzzer (6), g) due to of the short circuit, the flip-flop (4) is switched back to the oscillator (7) to put into action, whereby the luminescent diode (12) continues with the flashing frequency works and the output remains blocked, h) after the short circuit has been eliminated, the button (R) must be pressed again, so that the reset toggle stage (4) the flashing of the luminescent diode (12) is stopped, and the transistors (1,9) clear the way for undisturbed operation. 2. Signaling device according to claim 1, characterized in that that instead of said transistor (1) analogously thyristors or switching relays Can find application.