On the other hand, if we moved the probes back to 7.6V or 6.8V, respectively. It will also keep 0.7V across itself, resulting in a voltage deduction at each level. The silicon diode will conduct when its forward voltage reaches the voltage threshold, which is about 0.7V. But let’s use the easiest way possible by using a ladder regulator using diodes. We would need a constant voltage level to test and fine-tune. This circuit will alarm us when the 9V battery voltage level is lower than 8.3V. We assemble this circuit on a breadboard. Recommended: Recycle Free Li-ion battery from E-waste Experimenting with 9V battery alarm circuit Perforated board, wires, 8 pin socket for IC1 IC1: LM339 Voltage comparator IC: Buy HereīZ1: 6V-9V Active Electromagnetic Buzzer. What more? The experiment below will help us understand more. They will work at the low output voltage only. They are both connected to pin 2 (output) and positive voltage (+V). Then, we will add the LED1 and BZ1-buzzer as indicators of the output. On the other hand, if the voltage at pin 5 is less than at pin 4, Pin 2 will output almost no voltage at all. If the voltage at pin 5 is greater than at pin 4, Pin 2 will output a high voltage almost equal to the power supply. Both voltages are then compared by IC1 any result will be output to pin 2 (output). At the same time, some current from the 9V battery also flows through to a VR1 to the input pin 5 (non-inverting input), also known as a comparing voltage. ![]() The ZD1 works as a 6V Zener regulator to keep the reference voltage level at pin 4 (inverting input) of IC1. Then, R1 passes the safe current level to a 6V Zener diode (ZD1). Pin 12 is the negative power supply pin (-V).Pin 3 is the positive power supply pin (+V).There are two important pins of LM339 to see right now. This circuit consists of a few components (6 pieces without any capacitors), an LM339 Quad Comparator as the main component of this circuit, two resistors, a potentiometer, a Zener diode, an LED, and a buzzer.īy connecting both probes to a source-a 9V battery. It is a simple non-inverting comparator circuit. LED1 immediately will glow and BZ1 will emit sound. By installing this circuit to the output of the battery, if the battery voltage got to lower than 8.3V. Some circuits may misfunction when a 9V battery powering them voltage level got lower than 8V. Related Posts 9V Low Voltage Battery Alarm Circuit
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