Communications: electrical – Selective – Having indication or alarm
Patent
1982-07-12
1986-04-22
Caldwell, Sr., John W.
Communications: electrical
Selective
Having indication or alarm
340642, 340644, 340650, 340 52B, B60Q 126
Patent
active
045845557
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a circuit for reporting faults in a current consuming load connected to an electronic switching device wherein the fault is reported by means of an indicating device and with a control signal causing the load to be switched on being feedable to the input of the electronic switching device via a control line.
In such a circuit, as disclosed in DE-OS 22 03 426, faults are reported over a separate line leading to a display device common to a plurality of loads.
If a plurality of loads, particularly in a motor vehicle, are to be monitored individually, a large number of lines must be brought to the central operating location, namely one control line and one report line for each load.
SUMMARY OF THE INVENTION
It is the object of the invention to reduce the number of lines leading to the central operating location.
This is accomplished by according to the invention by a circuit for reporting faults in a current consuming load connected to an electronic switching device to whose input a control signal for causing the load to be switched on can be fed via a control line, wherein the input resistance of the electronic switching device is made variable by means of an impedance controlled by a fault signal and an indicator device for reporting a fault is actuated in dependence on the current flowing in the control line if the current in the control line deviates from the value at which it flows when there is no fault. Advantageous embodiments of the invention are defined in the dependent claims.
The invention results in the advantage that faults are indicated over the control line so that no separate report lines are required.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained with the aid of advantageous circuit examples which are illustrated in the drawings wherein:
FIG. 1 is a simplified illustration of the circuit according to the invention with an indictator element in the form of an indicator lamp;
FIG. 2 shows a modification of the circuit of FIG. 1 using a light emitting diode as the indicator element;
FIG. 3 shows modification of the circuit of FIG. 1 with an indicator device which additionally permits monitoring the brake light switch of a motor vehicle; and
FIG. 4 is a simplified illustration of a modification of the basic circuit according to the invention shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, an electronic switching device is marked with the reference numeral 1 and includes an input stage formed by a switching transistor 2 through which the current consuming load 3 connected to the positive pole of the voltage source is connected with ground potential which forms the negative pole. If the switch 4 disposed in a central operating location is closed, the base of transistor 2 receives, via a dropping resistor 5 and a control line 14, a control voltage which causes the load 3 to be switched on. The magnitude of this control voltage is fixed by Zener diode 6 at the value U.sub.z and is less than the voltage U of the voltage source by the voltage drop across the dropping resistor 5. This voltage U.sub.z is also present at the input of the window discriminator 7 which, however, at this value, does not permit current to pass through the indicator element, here shown as an indicator lamp 8.
Dropping resistor 5, window discriminator 7 and the indicator lamp 8 are combined in a display device 9 which is disposed in the area of the central operating location.
Fault detectors 10 and 11 are associated with the electronic switching device 1, with fault detector 10 transmitting a signal to OR gate 12 if the load is short-circuited and fault detector 11 transmitting a signal to OR gate 12 if the load current circuit is interrupted. The output signal produced at the OR gate 12 when there is a fault causes switch 13 to be closed. Switch 13 is preferably designed as a controllable semiconductor but could also be the closing contact of a relay actuated by the output signal of the OR gate 12. Switch 1
REFERENCES:
patent: 3550079 (1970-12-01), Clifford
patent: 3801975 (1974-04-01), Kitano
Transistor-Handbuch-Jansen, Franzis-Verlag, (1980), p. 303.
AEG Kabel Aktiengesellschaft
Caldwell Sr. John W.
Queen Tyrone
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