Communications: electrical – Systems – Selsyn type
Patent
1993-11-04
1996-02-20
Peng, John K.
Communications: electrical
Systems
Selsyn type
34031001, 34031004, 34082522, H04M 1104
Patent
active
054932670
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention pertains to an arrangement in an apparatus or a machine operated from the mains for the transfer of control commands to at least one working means in the apparatus or machine, such as a motor or the like, via a wire also used for the power supply to the working means. The arrangement includes a control unit provided for creating a control command by suppressing, in a predetermined order, at least part of one or several consecutive half-periods of a predetermined polarity of the supply voltage, and a slave unit operating in response to the control command transmitted to activate the working means.
In the U.S. Pat. Nos. 4,007,458 and 4,131,882 there are disclosed arrangements as described above. However, in these references the arrangements have been used in irrigation systems including a great number of valves and the object has been to convey out, in a simple way by means of the power supply cable, control commands for the control of the different valves.
If an arrangement of the kind described is to be used in an apparatus or a machine having several working means with inductive properties, such as motors, it has been difficult for the slave unit to interprete the control command if being sent while any such inductive working means is operating. The change in a number of half-cycles, obtained by suppressing of at least part of the cycle, is counteracted by the repugnance of the working means against changes and, as a result, the slave unit will experience difficulties in unambiguously identifying a control command being sent.
SUMMARY OF THE INVENTION
An object of the invention is to remedy the problems present in the prior art and to provide an arrangement of a design such that control commands transmitted by a control unit can be unambiguously interpreted by a slave unit for the correct control of the working means to be operated. The object is achieved by a design of the control unit wherein, before a control command is transmitted, the control unit operates to shortly disconnect the supply voltage on the wire for a period of time required for the current in the working means to decline essentially to zero.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described more in detail in connection with an embodiment with reference to the enclosed drawings, in which:
FIG. 1 shows a block diagram of the arrangement according to the present invention;
FIG. 2 schematically shows a control unit according to the invention;
FIG. 3 schematically shows a slave unit having a working means connected to it; and
FIG. 4 and 5 show diagrams of waveforms of signals transferred between the control unit and the slave unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The illustrated and preferred embodiment of the present invention is intended to be used in a dishwasher, the main function and design of which being conventional. Accordingly, no detailed description of the dishwasher will be given and the dishwasher will only be commented on in general terms when needed. Hence, such a machine may comprise a dishwashing compartment supplied with water via a solenoid valve and drained of cleaning and rinsing liquid via a drainage pump. Further, in such machine a circulation pump is provided for the supply of cleaning and rinsing liquid to rotating spray-arms provided with holes and spraying liquid, in a conventional way, onto dish goods supported in baskets in the dish-washing compartment. For the dosage of detergent there is provided a dosing device which via a door, which can be opened by magnetic means, supplies a dose of powder from a dosage compartment covered by the door. Accordingly, the various working means which in this case have to be controlled by a programmer are the circulation pump, the drain pump, the dosage device and the solenoid valve. Preferably, in this case the programmer is of the electronic type and includes a microprocessor, a program memory and additional electronic components.
In the following description the control components
REFERENCES:
patent: 4007458 (1977-02-01), Hollabaugh
patent: 4477763 (1984-10-01), Asano et al.
patent: 4706180 (1987-11-01), Wills
patent: 4719400 (1988-01-01), Kurakake et al.
patent: 4990908 (1991-02-01), Tuny
patent: 5146146 (1992-09-01), Samann
patent: 5200684 (1993-04-01), Fisher
patent: 5331537 (1994-07-01), Skarpatowski
patent: 5355070 (1994-10-01), Cocconi
Ahlse Marc R.
Castwall Lennart W.
Moren Lars G.
Aktiebolaget Electrolux
Mannava Ashok
Peng John K.
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