CFL bulbs are being replaced with DIY LED Light Bulb (LED Lamp) which are becoming increasingly widespread. People are gradually switching to LED lamps in their homes and offices as the cost of LED light bulbs falls. We’ll try to construct a DIY LED Light Bulb or a DIY LED Lamp out of an old LED Lamp housing in this project (case).
The LED Driver’s design is very crucial in this DIY LED Light Bulb. The LED Driver can be designed in one of two ways: with a switching mode power supply or with a standard transformer-based linear regulator.
But for this DIY LED light bulb, we will be designing a transformer less power supply to act as the LED Driver. In fact, this type of power supply for LED Lamps is becoming more common (well, at least for lower wattage LEDs).
Warning: This DIY LED Light Bulb will work directly from the main supply i.e. 230V AC. You need to be very careful when working on AC Supply.
Warning: Designing Transformer less power supply without the knowledge of how the components work can be fatal.
- DIY LED Light Bulb Circuit Diagram
- Components Required for DIY LED Light Bulb
- Component Description
- X – Rated Capacitor
- Circuit Design of DIY LED Light Bulb
- PCB Design of DIY LED Light Bulb
- Assembling the LED Light Bulb
- Working of the LED Light Bulb
DIY LED Light Bulb Circuit Diagram
Components Required for DIY LED Light Bulb
- C1 – 135J 400V Metal Film Capacitor
- B1 – Bridge Rectifier (4 Diodes can be connected in Full wave Rectifier mode)
- C2 – 22µF 35V Electrolytic Capacitor
- R1 – 100KΩ Resistor (1/4 Watt)
- LED 1 to 12 – 8mm LEDs
Component Description
X – Rated Capacitor
The main component of the Transformer Less Power Supply Design for the DIY LED Light Bulb is the X – Rated Capacitor. It is a metal film capacitor that is often used as a safety capacitor.
An X – Rated capacitor is placed between the line and neutral. If this capacitor fails due to overvoltage, the fail will be a short and the excess current will blow the fuse and hence avoiding any electrical shocks.
Circuit Design of DIY LED Light Bulb
First, the main supply is given to the metal film capacitor. The other end of the capacitor is connected to the AC input of a bridge rectifier. To be on a safer side, connect a 100Ω 1W Resistor in series with the X – Rated Capacitor to act as a fuse (not shown in the circuit).
NOTE: If you do not have a bridge rectifier, you can connect 4 PN Junction Diodes (like 1N4007) in full wave rectifier mode.
The AC Power Supply’s Neutral is linked to the other AC Input of the Bridge Rectifier. A capacitor receives the rectified output (C2). Across the capacitor, 12 8mm LEDs are linked in series.
The R1 resistor will be used as a bleeder resistor (it will discharge the capacitor in the event of power failure or if LED fails).
NOTE: We removed a broken LED light bulb and reassembled the circuit, which was very similar to the one we designed. The key distinction is that they used SMD components for LEDs and the bridge, whereas we used through–hole components (for obvious reasons).
PCB Design of DIY LED Light Bulb
In order to design the PCB Layout of the LED Light Bulb, we have used the Eagle CAD. The following image shows the PCB Layout of the LED Light bulb. We have made the PCB using Toner Transfer Method as mentioned in this tutorial: How to make your Own PCB at Home.
Assembling the LED Light Bulb
Assemble all the components as per the layout and solder them. We have got an empty LED Housing from an old LED Lamp. After assembling the PCB, we mounted the board in the LED Housing with all the wires.
Working of the LED Light Bulb
Now we’ll have a look at how this simple LED light bulb works.
LEDs require very little current to function. In a typical transformer-based regulated power supply, series resistors are used to regulate and control the current. The current is controlled or limited by the X – Rated Capacitor in the transformerless power supply.
The overall current available in the circuit is restricted by the capacitor’s reactance because it is linked in series with the AC supply.
he reactance of a capacitor can be calculated using the following formula:
XC = 1/2πFC Ohms, where F is the frequency of the supply, C is the capacitance of the capacitor.
In our case, we have used a 1.3µF Capacitor. Hence, the reactance of this capacitor is
XC1 = 1 / (2*π*50*1.3*10-6) = 2449.7 ≈ 2450 Ω.
Therefore, the current through this capacitor is given by I = V / XC1 Amps = 230 / 2450 = 93.8mA.
Now, the current limited AC is given to the Bridge Rectifier. The output of the bridge will be 230V DC. This is given to a filter capacitor of rating 35V. But the peak to peak ripple voltage across the Capacitor C2 is around 44V.
This is given to 12 LEDs in series and hence each LED will take up around 3.7V, which is equal to the rated voltage of the 8mm LED.
As far as the power is concerned, the total power output by the LEDs is around 4W.
Important Note: This project is just a demonstration of How to design an LED Light Bulb and How an LED Light Bulb works. The method mentioned in this project might not be suitable for practical usage.
Also, the project involves working around 230V AC Mains Supply. You need to be extremely careful when working with AC Supply.
