Battery undervoltage indicator ----- Low Battery INDICATOR

Keywords: LM319, NE555, undervoltage indicator circuit Some rechargeable batteries are specified. The discharge cannot be placed below a certain voltage. The circuit provided here can indicate that the end voltage of a 12V charging battery has dropped to the termination voltage. The indication method is expressed in a way of flashing in an LED. The comparator chip LM319 (IC1) is designed as a circuit core. The LM319 is a high speed dual comparator chip. This article only uses one of the comparators. The 1.2V reference voltage of the comparator is generated by the band gap regulator diode D1 (LM385), which is added to the in-phase input foot of the comparator. The voltage of R2, R3 and VR1 voltage divider is sent to the inverted input of the comparator. At the beginning, if the battery voltage is sufficient, the voltage in which the comparator inverted input feet should be higher than the voltage of the same phase input feet, and the output of the comparator is low. The IC2 constitutes a multi-resmicker by a 555 chip. It does not ignore when the reset pin 4 is at a low potential. Since the 4 foot of IC2 is connected to the output of the comparator. Therefore, the battery voltage does not oscillate when the battery voltage is normal, and the resulting LED1 does not flash. If the battery voltage is dropped to 10.5V. Then the voltage of the comparator inverted input feet can be adjusted by VR1, which is slightly lower than 1.2V, and the result comparator output is high, and IC2 is activated to start oscillating. At this time, the LED1 emits flash, indicating that the battery voltage has been reduced to a predetermined limit. It is necessary to charge immediately to continue to use. Both IC1 and IC2 work with 5V DC voltage output from IC3.

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