Vehicle battery state of charge indicator - has transistor switching off when series Zener diode is non-conducting due to low voltage, illuminating parallel electroluminescent diode

摘要

The state of charge of motor vehicle battery is shown by electronic indicator which has low power consumption and improved reliability since there are no moving parts. A generator (G) charges the vehicle battery (Vo) to which a transistor (T1) base is connected via a zener diode (D2) and a series resistor (R2). When the battery voltage is below nominal value the diode does not conduct and the transistor is cut-off. In this condition an electroluminescent diode (D1) with a series resistor (R1) connected to the battery is illuminated. As battery voltage increases the transistor draws the collector current to extinguish the diode.