A simple yet highly effective emergency lamp circuit that uses the integrated circuit LM358 serves as an essential apparatus for providing backup illumination during instances of power outages.
The circuit design presented herein is a multifunctional emergency lighting solution that guarantees consistent and automatic lighting in the event of a power disruption.
Central to this circuit is the LM358 operational amplifier, which plays a pivotal role in sensing the occurrence of power failures and subsequently managing the operation of the lamp.
To energize this circuit, a 12V battery should be utilized as the power source.
Circuit Working:
Parts List:
| Component | Value/Type | Quantity | Power Rating |
|---|---|---|---|
| Resistors | |||
| 100k | 4 | 1/4 Watt | |
| 3.9k | 2 | 1/4 Watt | |
| 470Ω | 1 | 1/4 Watt | |
| 100Ω | 1 | 1/4 Watt | |
| 220Ω | 1 | 1/2 Watt | |
| Potentiometer | 5k | 1 | – |
| Capacitors | |||
| Ceramic Capacitor | 0.01µF | 1 | – |
| Electrolytic Cap. | 10µF 25V | 2 | – |
| Semiconductors | |||
| IC | LM358 | 1 | – |
| Transistor | 2N2222 | 1 | – |
| Transistor | TIP32 | 1 | – |
| Other Components | |||
| Switch | ON/OFF | 2 | – |
| Fuse | 2A | 1 | – |
| Battery | 12V | 1 | – |
The circuit above uses operational amplifiers chip called the IC LM358.
The amplifier IC1 acts like an oscillator and works as a comparator.
It creates a pulse signal that can make something flash or stay on depending on where switch S1 is set.
Its job is to control the switching of two transistors Q1 2N2222 and Q2 TIP32.
The resistor R1 is key for setting the oscillation frequency of the integrated circuit IC1
At the same time R5 is crucial for controlling the base current that goes into the transistor Q1.
R6 also has an important job it limits the current that goes to the base of transistor Q2 making sure it turns on and off correctly.
R7 helps keep the circuit stable while also controlling the current flow.
Resistors R8 and R9 work together to form a voltage divider, which is necessary for biasing the integrated circuit.
Capacitor C2 is responsible for smoothing out the signal, which helps with the timing functions in the circuit.
For power supply stability capacitor C3 plays a vital role in reducing voltage changes ensuring everything runs smoothly.
The switch S1 can change between Dim and Flash modes controlling how the emergency lamp works by affecting IC1 which acts as an oscillator.
The potentiometer VR1 is used to adjust the sensitivity of the operational amplifier integrated circuit which is important for setting the voltage level that decides when the emergency lamp turns on or off.
When the main power is on the battery stays ready and the lamp does not light up.
But if the power goes out the circuit can sense the drop in voltage.
This causes Q2 to turn on which automatically lights up the 12V lamp.
Formulas with Calculations:
Below mentioned are the formulas with calculations for Simple Emergency Lamp Circuit using IC LM358:
Oscillation Frequency Calculation IC1:
The frequency of the oscillator circuit using IC1a is determined by the resistor-capacitor network:
f = 1 / (2π × √(R1 × C1 × C2))
where,
R1 is 100kΩ
C1 is 0.01µF
C2 is 10µF
Calculation:
f = 1 / (2 × 3.1416 × √(100,000 × 0.01 × 10 × 10⁻⁶))
= 1 / (6.2832 × √(0.01))
= 1 / (6.2832 × 0.1)
= 1 / 0.6283
= 1.59 Hz
Transistor Base Current Calculation Q1 & Q2 Switching:
The base current of transistor Q1 2N2222 is calculated as follows:
I_B = (V_out – V_BE) / R5
where,
- V_out is 12V from op-amp
- V_BE is 0.7V base emitter voltage drop
- R5 is 470Ω
Calculation:
I_B = (12 – 0.7) / 470
= 11.3 / 470
= 24mA
Collector Current Calculation for Q2 TIP32 Driving the Lamp:
The collector current for Q2 is determined by:
I_C = β × I_B
where,
- β is the current gain of TIP32 to 100
- I_B from above calculation is 24mA
Calculation:
I_C = 100 × 0.024
= 2.4A
Since the lamp requires 2A this transistor is suitable for switching it.
Power Dissipation in Resistor R6 220Ω 1/2W:
Power dissipation in a resistor is given by:
P = I² × R
where,
I = 24mA = 0.024A
R6 = 220Ω
Calculation:
P = (0.024)² × 220
= 0.000576 × 220
= 0.127W
Since, R6 is rated at 1/2W (0.5W) it is well within safe operating limits.
How to Build:
To build a Simple Emergency Lamp Circuit using IC LM358 following steps are required for connections of the circuit:
- Gather all the components as mentioned in the above circuit diagram
- Connect pin 1 of IC1 to pin 3 of IC1 through resistor R1.
- Connect pin 2 of IC1 to GND through capacitor C1.
- Connect pin 3 of IC1 between resistors R8 and R9
- Connect pin 4 of IC1 to GND.
- Connect pin 5 of IC1 to pin 2 of IC1
- Connect resistor R2 from pin 1 of IC1 to pin 2 of IC1.
- Connect anode of capacitor C2 from pin 5 and pin 2 and cathode of C1 connect to one end of switch S1 and other end of switch connect to GND.
- Connect pin 6 of IC1 to center leg of VR1 pot and upper leg of VR1 connect to resistor R3 and 3rd leg of pot connect to resistor R4.
- Connect pin 7 of IC1 to base of transistor Q1 through resistor R5.
- Connect pin 8 of IC1 to positive terminal of 12V battery.
- Connect collector of transistor Q1 to resistors R6 and R7
- Connect emitter of transistor Q1 to GND of the circuit.
- Connect base of transistor Q2 between resistors R4 and R7
- Connect collector of transistor Q2 to one end of 12V bulb and other end of bulb connect to GND
- Connect the emitter of transistor Q2 to positive supply of circuit.
- Connect one end of S2 switch from positive supply of the circuit and other end connect to fuse and other end of fuse connect to positive of +12V battery and negative of battery connect to GND.
- Connect positive of capacitor C2 to positive supply of the circuit and negative of capacitor connect to GND.
Conclusion:
This Simple Emergency Lamp Circuit using IC LM358 gives you automatic backup lighting and can even flash if you want it to.
It uses an LM358 op-amp to sense when the light is out and control the system, plus transistors to help switch things on and off.
This design is perfect for DIY electronics fans who want an easy and effective way to create emergency lights.