Battery voltage monitor circuit by LM339
This low voltage circuit can be used to monitor battery and other voltage sources of current for problems. The circuit sounds an alarm and lights an LED, but can be interfaced to any number of other circuits for many different uses.
We use The LM339 14pin Compare voltage IC is base of this circuit. when attack the probe input to battery, voltage through the input pin of IC1 and compared with the reference voltage of the zener diode, when the voltage is lower, will be have voltage output made LED1 is light and buzzer work there are sound. by you can adjust sentility 0f circuit by control VR1.
R1,R2_________1K 1/4W Resistors
IC1___________LM339 Voltage comparator IC
ZD1___________Zener Diode 6V 0.5W no. 1N5233
LED1__________Any color you like.
P1,P2_______Probes (See Notes)
MISC1 Board, wire, socket for IC
1. The circuit will operate from 9V to 12V.
2. Adjust R2 until the alarm goes off at the correct voltage.
Bargraph Voltage Indicator by LM339
The circuit Bargraph Voltage Indicator used IC op-amp two quad voltage comparators to illuminate a series of 4 LEDs indicating volume level.
The op-amp used in this particular circuit is the LM339. It is a popular IC and should be available from many parts stores.
The 1K resistors in the circuit are essential so that the LED’s turn on at different Voltage input levels.
The sensitivity can be decreased with R1 and the input control to read higher levels.
This circuit is easily expandable with more op-amps, and is not limited to use with the LM339.
Detail more,Plaese read in image.
Level Detector by IC LM741
If you have limit parts, only IC 741 and LED. I think this Ideal good for you.
This circuit be the circuit checks voltage is easily. Or Level Detector by IC LM741 highly popular. By R1 keep fine the value voltage referable of the circuit. If Vin be valuable more than volt. The referable LED stick bright.
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