| 摘要 |
An electronic safety device for automatically interrupting the supply of electric current to a heating resistor of an iron at the end of a predetermined interval of non-use, comprising a movable body adapted to control a position of contacts of an associated switch so that at least one opening-closing sequence of the switch contacts is obtained upon displacement of the movable body. Associated with the switch is a resistor bridge supplied with a rectified voltage E and comprising a first resistor R1 and a second resistor R2 in series with the switch contacts. A capacitor is connected to the terminals of resistor R2, a voltage Vo being collected at the terminals of said resistor R1 and being applied to one input of a counter which is reset to zero each time voltage Vo is higher than E/2, that is, upon closing of the contacts. The counter is connected to an input of a comparator for transmitting a voltage V1 when the counter attains a predetermined counting threshold. The comparator is connected to a trigger of a triac having one terminal connected to a current supply and another terminal connected in series to the heating resistor. The comparator is adapted to deliver turn-on pulses to the trigger as long as no voltage V1 is applied and to stop these turn-on pulses as soon as a voltage V1 is applied, thereby interrupting the current supply to the heating resistor.
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