Voltage Level Monitoring Circuit using IC LM339

Voltage Level Monitoring Circuit using IC LM339 very important in modern electronics, as it helps system work correct.

To see voltage in real time we need to use voltage level readout circuit.

This circuit uses LM339 comparator IC for accurate voltage check and stable reading.

Main parts are LEDs that show voltage level and resistors divide voltage.

Circuit works well with 12V power and is good for many uses.

IC LM339 is fast and uses low power and is so good for battery devices.

Resistors help split voltage and IC LM339 compare it to fixed levels.

LEDs turn ON/OFF based on comparator output and it shows voltage level clearly.

This introduction tells basic idea of Voltage Level Monitor Circuit with few parts and how it works.

Using this circuit helps improve system safety and performance.

Circuit Working:

Parts List:

This circuit easy to build on normal PCB.

Design uses voltage divider with same 1k resistors to give reference voltage.

Voltage divider and power supply go to non-inverting pins of comparators.

If 12V is over four 1k resistors then each get 3V (12V ÷ 4).

Input signal goes to inverting pins of comparators.

Comparator output works like sink and LED turns ON when input voltage is greater then reference voltage.

Output is not connected to voltage source but to ground.

So load LED connects between output pin and Vcc.

LED anode goes to Vcc and cathode goes to output.

Input signal goes to inverting pin with reference voltage to non-inverting.

To change reference levels for low input add resistors in series with R1 to R4.

Total voltage across these resistors is: Vt = Vcc – VR5.

Formulas:

We can use LM339 comparator IC to make voltage level monitor circuit.

Resistor voltage divider gives reference voltage to comparator input.

Below is simple formula and connection details.

Reference Voltages:

Resistors R1, R2, R3, R4 make voltage divider and this gives Vref to comparator pins.

Pin 5 (Vref5):

Vref5 = Vcc × (R2 / (R1 + R2)) = 12V

Pin 7 (Vref7):

Vref7 = Vcc × (R3 / (R2 + R3)) = 12V

Pin 9 (Vref9):

Vref9 = Vcc × (R4 / (R3 + R4)) = 12V

Pin 11 (Vref11):

Vref11 = 0V (this pin go to GND)

How to Build:

To build a Voltage Level Monitoring Circuit using IC LM339 follow the steps below for connections:

• Collect all parts as in circuit diagram.
• Pin 1 of LM339 connects to cathode of LED2 and resistor R7 560Ω.
• Pin 2 connects to cathode of LED1 and resistor R6 560Ω.
• Pin 3 connect to +12V Vcc.
• Pins 4, 6, 8, 10 connects to input voltage +Vin.
• Pin 5 goes between R5 100k and R1 1k.
• Pin 7 goes between R1 1k and R2 1k.
• Pin 9 connects between R2 1k and R3 1k.
• Pin 11 connects between R3 1k, R4 1k, and GND.
• Pin 12 connect to GND.
• Pin 13 goes to cathode of LED4 and resistor R9 560Ω.
• Pin 14 goes to cathode of LED3 and resistor R8 560Ω.
• Anode of all LEDs connects to +12V.
• R5 100k connects to +12V and pin 5.

Conclusion:

This Voltage Level Monitoring Circuit using IC LM339 uses 1k resistors to make voltage divider and give reference to comparator.

IC LM339 compare input voltage with these levels to control LED ON/OFF.

We can change reference voltage using more resistors in series.

It is easy to build on PCB or dot board as it is good in many electronics projects.

References:

Datasheet IC LM339