Regulated power supply with overload alarm, 220/0-15 volts 1 amp. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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Sound signaling allows the user to quickly respond to an emergency situation if, during experiments with various electronic equipment, an overload of the power source occurs. The power supply circuit with an audible signaling device for exceeding current consumption is shown in the figure.
The VD1-VD4 diode rectifier is powered by a transformer whose secondary winding is designed for a voltage of 18 V at a load current of at least 1 A.
The adjustable voltage regulator is made on transistors VT2...VT5 according to a well-known scheme. Variable resistor R3 at the output of the stabilizer can be set to a voltage of 0 to +15 V.
The signaling device, indicated on the diagram by device A1, is an audio frequency generator with an acoustic emitter connected to it (sound dynamic head, piezoelectric acoustic transducer, etc.). Its schematic diagram is not given, since the designer can choose a more acceptable sound design for him (tonal frequency, siren, multi-tone trill, melody, imitator of various sounds).
The diagram of the device shows only the key that controls the operation of the signaling device on the transistor VT1.
The load current (DUT) flows through the resistor R2, creating a voltage drop across it. While the current is small (with the selected value of this resistor no more than 0,3 A), transistor VT1 is closed.
As the current consumption increases (and, accordingly, the voltage across the resistor increases), the transistor approaches the opening threshold. When the voltage between the base and emitter of the transistor VT1 reaches 0,7 V, it opens and, with a further increase in current, goes into saturation.
When the transistor opens, the rectified voltage is supplied to the acoustic signaling device and activates it.
In the described power source, it is possible to use domestic element base. Transistors. BC237 are interchangeable with KT639B; VS327 - on KT361B and BD283 - on KT815A.
Instead of diodes 1N4001, rectifier diodes KD212B or diode bridge KTs405E are suitable. KS515A should be used as a zener diode. The power dissipation of the resistor R2 is taken with some margin based on the increased current consumption, for example, 1 W.
Author: Khaloyan A.A.
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