A Simple Battery Level Indicator Circuit using IC MN13811 is really important for keeping track of how much power is left in batteries and letting you know when it i time to recharge them.
This specific circuit uses an MN13811 integrated circuit and two transistors that work together to light up an LED which shows when the battery is low.
It is perfect for small battery powered devices that run on 3V.
Plus, this circuit is super energy efficient using only about 1 microampere when it is not doing anything and just 20 microamperes when the LED is flashing.
Circuit Working:
Parts List:
| Component | Specification | Quantity |
| Resistors (1/4 watt unless specified) | ||
| 4.7M | – | 1 |
| 4.7k | – | 1 |
| 10k | – | 1 |
| 680Ω | – | 1 |
| 100Ω | – | 1 |
| Capacitors | ||
| Ceramic | 0.68µF | 1 |
| Electrolytic | 100µF 25V | 1 |
| Semiconductors | ||
| IC | MN13811 | 1 |
| Transistor | BC557 | 1 |
| Transistor | BC547 | 1 |
| LED | Any 5mm 20mA | 1 |
| Battery | 3V | 1 |
In this article the MN13811 integrated circuit is designed to keep an eye on how well a battery is working.
It checks the batteries voltage and sends out a signal when the voltage drops below a certain point.
The voltage monitoring happens at pin 2 which is called V+.
As long as the battery voltage is above this important level the output from the circuit stays low keeping the transistors turned off.
But when the battery voltage goes below that set point the circuit sends a high signal from pin 1.
This turns on transistor Q1 BC557 which then activates transistor Q2 BC547.
When Q2 is turned on the LED1 lights up showing that the battery is low and needs to be charged or replaced.
Formulas with Calculations:
Below are the formulas with calculations for Simple Battery Level Indicator Circuit using IC MN13811:
The MN13811G IC works at a set threshold voltage which is usually between 2.9V and 3.0V.
The cutoff voltage is determined by the voltage divider made up of R1 and R2.
Threshold Voltage Calculation:
V_threshold = V_battery * (R2 / (R1 + R2))
where,
- V_battery = 3V
- R1 = 4.7M
- R2 = 4.7k
Now, calculating:
V_threshold = 3V × (4.7k / (4.7M + 4.7k))
= 3V × (4700Ω / (4,700,000Ω + 4700Ω))
= 3V × (4700 / 4,704,700)
= 3V × 0.000999
= 2.997V approximately 3V
So, the circuit will activate when the voltage drops close to 3V.
Using the given resistor values the circuit is set to activate the LED when the voltage drops below 3V.
LED Current Calculation:
I_LED = (V_supply – V_LED) / R5
where,
- V_supply = 3V
- V_LED = 1.8V
- R5 = 100Ω
Now, calculating:
I_LED = (3V – 1.8V) / 100Ω
= 1.2V / 100Ω
= 12mA
This ensures that the LED gets sufficient brightness without excessive power consumption.
How to Build:
To build a Simple Battery Level Indicator Circuit using IC MN13811 follow the below mentioned steps:
- Assemble all the components as mentioned in the above circuit diagram.
- Connect the positive terminal of the 3V battery to the V+ pin 2 of the MN13811 IC.
- Connect pin 3 of the IC to the negative terminal GND of the battery.
- Connect a 100uF capacitor C2 across the power supply to stabilize the voltage.
- Connect a 4.7M resistor R1 between pin 1 of the IC and the base of Q1 BC557
- Connect a 0.68uF capacitor C1 between pin 1 IC1
- Connect the collector of Q1 to the base of Q2 through a 4.7k resistor R2
- The emitter of Q1 is connected to the positive supply rail and the collector of Q2 is connected to ground.
- Connect the LED1 in series with a 100Ω resistor R5 to the collector of Q2.
- Connect resistor R3 from positive rail to junction of resistor R4 and LED1.
- Connect resistor R4 between capacitor C1 and resistor R3
Conclusion:
This Simple Battery Level Indicator Circuit using IC MN13811 shows when the battery is low by using an LED light.
The MN13811 IC helps keep track of the battery level accurately and the transistors work like a switch to turn on the LED.
This circuit is perfect for devices that run on batteries and need to keep an eye on their battery health.