Battery Status Indicator Circuit are really important for keeping batteries in good shape and making sure they work well in different electronic devices.
The circuit that uses three LEDs is a simple but super effective way to check the batteries voltage and show how it is doing by lighting up these three different LEDs.
Each LED represents a certain voltage level so you can easily see the batteries status at a glance, whether it is low, normal or fully charged.
Circuit Working:
Parts List:
| Component | Specification | Quantity |
|---|---|---|
| Resistors | 1k | 3 |
| 3.3k | 4 | |
| 100k | 1 | |
| Transistors | BC547 | 2 |
| BC557 | 1 | |
| LEDs | Red, Green, and Blue 5mm 20mA | 1 each |
| Diodes | 1N4148 | 5 |
| Zener Diodes | 10V 1/2 watt | 1 |
| 12V 1/2 watt | 1 |
The circuit diagram shown in this article includes several simple parts like transistors, resistors, diodes and Zener diodes.
The LEDs act as visual signals to show the batteries status.
When the battery voltage drops below a certain level like 10 volts, the Zener diode D4 which is set at 10 volts starts to conduct.
This allows current to flow through resistor R4 turning on transistor Q2 which makes LED1 light up to show that the voltage is low.
If the battery voltage is between 10 volts and 12 volts Zener diode D6 still works while transistor Q3 gets activated because Zener diode D7 rated at 12 volts is not conducting.
This makes LED2 turn on indicating that the battery is in a normal voltage range.
Lastly, when the battery voltage goes over 12 volts Zener diode D7 starts to conduct which turns off Q3 and activates Q1.
This causes LED3 to light up showing that the battery is fully charged.
Note: The battery to be monitored should be connected between the terminals A and B.
Formulas with Calculations:
The formulas with calculations for Simple 3 LEDs Battery Status Indicator Circuit is mentioned below:
Base Resistor Calculation:
To ensure proper transistor operation the base current (Iᵢ) is calculated using the formula:
Iᵢ = Iₚ / hFE
where,
- Iₚ is the collector current.
- hFE is the current gain of the transistor.
For example, if Iₚ is 10mA and hFE is 100:
Iᵢ = 10mA / 100 = 0.1mA
The base resistor (Rᵢ) is then calculated using:
Rᵢ = (Vₑ – Vₒₗ) / Iᵢ
where:
- Vₑ is the input voltage.
- Vₒₗ is the base emitter voltage around 0.7V
LED Current Limiting Resistors:
The resistor values for LEDs are calculated using:
R = (Vₑ – Vₚ) / Iₑ
where:
- Vₑ is the supply voltage.
- Vₚ is the forward voltage of the LED.
- Iₑ is the desired current around 10 to 20mA
How to Build:
To build a Simple 3 LEDs Battery Status Indicator Circuit follow the below mentioned steps for connections:
- Gather all the components as mentioned in the above circuit diagram.
- Connect collector of transistor Q1 to positive supply through LED1 and resistor R1 in series.
- Connect base of transistor Q1 to collector of transistor Q2 through resistor R2.
- Connect the emitter of transistor Q1 to GND.
- Connect the collector of transistor Q2 to positive supply through LED2 and resistor R3 in series.
- Connect the base of transistor Q2 to one end of resistor R4 and connect other end of resistor R4 between diode D4 and resistor R5.
- Connect emitter of transistor Q2 to GND.
- Connect diodes D2, D3 and D4 from positive supply and one end of resistor R5 in series and other end of resistor R5 to GND.
- Connect the collector of transistor Q3 between LED2 and resistor R3, an connect resistor R6 and LED3 in series from collector of transistor Q3 and GND.
- Connect the emitter of transistor Q3 to positive supply.
- Connect the base of transistor Q3 to resistor R7 as shown in circuit diagram.
- Connect resistor R8 from positive supply with diodes D5, D6 and D7 in series and GND.
Conclusion:
This Simple 3 LEDs Battery Status Indicator Circuit is a easy way to check battery voltage levels.
It uses Zener diodes and transistors to tell if the battery is low, normal or fully charged.
This project is great for people who love electronics as it helps you learn about basic parts and how circuits work.