| 摘要 |
The LED indicator is used in devices and systems for indicating that a certain voltage threshold has been exceeded. The indicator has low power loss, and causes the LED to blink when voltage is present. The indicator includes two npn transistors (1) and (2), with the base of the second transistor (2) connected to the first of resistors (3) and (4). The other terminal of the second resistor (4) is connected to one of the terminals of the first capacitor (5) and, through a third resistor (6), to the cathode of diode (7), whose anode is connected to the positive terminal of the power source. The other terminals of capacitor (5) and resistor (3), as well as the emitter of npn transistor (2) are all grounded. The collectors of the npn transistors (1) and (2) are connected to the base of the first pnp transistor (8) and, through a fourth resistor (9), to one terminal of the first capacitor (5), to one terminal of a fifth resistor (10), to the anode of LED (11), and to the emitter of the first pnp transistor (8), whose collector is connected to the base of the first npn transistor (1). The other terminal of the fifth resistor (10) is connected to the cathode of LED (11), to the base of the second pnp transistor (12), and to the collector of the third pnp transistor (13), whose base is connected to the collector of the second pnp transistor (12) and to the emitter of the same transistor through the sixth resistor (14). The emitter of the third npn transistor (13) grounded, and to one terminal of the second capacitor (15), whose other terminal is connected, through the seventh resistor (16), to the emitter of the first npn transistor (1) and, through the eighth resistor, to the emitter of the second pnp transistor(12).<IMAGE>
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