LED lights have become super popular lately.
They are also called solid state lamps or LED bulbs.
These lights are great for saving money on electricity because they use much less power than other bulbs, typically only 0.5 to 3 watts.
In 2010, they were not quite as bright as some other bulbs, but this guide will show you how to build your own simple LED bulb circuit!
We will talk about the benefits of LED lights, the different colors they can be, and how to put your bulb together.
What is a LED Bulb Circuit:
A LED bulb circuit is an electronic circuit that powers and controls the light emitting diodes LEDs in an LED light bulb.
LED bulbs are energy efficient alternatives to traditional incandescent or fluorescent bulbs, and they operate using semiconductor technology to produce light.
The circuitry within an LED bulb is responsible for converting electrical power into light regulating the current, and providing any additional features such as dimming or color changing capabilities.
Circuit Working:
Parts List:
| Category | Component | Quantity |
|---|---|---|
| Resistors | 1M CFR (1/4W) | 2 |
| 100Ω 1W CFR | 3 | |
| Capacitors | PPC 0.33µF 400V | 2 |
| Electrolytic 47µF 100V | 1 | |
| Semiconductors | Diode 1N4007 | 8 |
| LEDs 30mA 5mm | 9 |
LED Characteristics and Development:
LEDs are undergoing rapid technical development resulting in an annual increase in power and light output.
White LEDs, the preferred choice for many applications offer various light temperatures from warm white resembling conventional bulbs to daylight 2700 to 10,000k.
The choice between point and diffuser LEDs further extends to different radiation angles ranging from 10° to 150°.
As technology progresses, the price of LEDs continues to decline accompanied by an increase in luminous efficiency.
To facilitate the conversion of intensity to light flux an online calculator is available.
Power Supply
Powering LED bulbs from the mains requires a suitable power supply.
For low power and small sizes transformers are not ideal making the use of a capacitance based power supply common.
A capacitor with AC 250V~ best in class X2 is often employed, with a series resistance 220Ω to 2.2kΩ to limit inrush current.
A parallel security resistor around 1M ensures capacitor discharge after switching off.
The reduced voltage is rectified by a small diode bridge.
The online calculator aids in determining component values for LED bulbs, with a common LED size being 5mm.
Formulas and Calculations:
Here we can estimate the current output of a transformerless power supply with a 0.33uF capacitor for two common mains frequencies: 50Hz and 60Hz.
Here is the calculation mentioned below:
Capacitance (C): 0.33 microFarads (uF) = 0.33 x 10-6 Farads (F)
Formula: Xc = 1 / (2 * π * f * C)
where,
- Xc is the capacitive reactance in ohms Ω
- π (pi) is a mathematical constant approximately 3.14159
- f is the mains frequency in hertz Hz
Calculations:
For 50Hz Mains:
- Xc_50Hz = 1 / (2 * π * 50Hz * 0.33 x 10-6F)
- Xc_50Hz = 9.55 kΩ (kilo-ohms)
For 60Hz Mains:
- Xc_60Hz = 1 / (2 * π * 60Hz * 0.33 x 10-6F)
- Xc_60Hz = 7.96 kΩ (kilo-ohms)
We may estimate the current using the following simplified formula as the capacitor serves largely as a reactance in the circuit:
I = Vin / Xc
where,
- I is the current in milliamps (mA)
- Vin is the mains voltage (Warning: Mains voltage is dangerous, so never measure it yourself unless you are a qualified electrician)
Important Reminder:
Not all circuit factors are taken into account by this simplified technique.
Furthermore, you should never measure mains voltage yourself for safety reasons.
Assuming a typical mains voltage of 120V (US) or 230V (Europe), here is a rough estimate of the current output:
- For 50Hz (120V or 230V): I = Vin / Xc_50Hz = 12.6 mA (120V) or 24 mA (230V)
- For 60Hz (120V or 230V): I = Vin / Xc_60Hz = 15.1 mA (120V) or 29 mA (230V)
Note:
These are only approximations, because of safety margins, power dissipation and capacitor quality the actual current output may be less.
For the majority of LEDs, a transformerless power supply with a 0.33uF capacitor most certainly wont produce enough current.
Construction Details
LED Selection:
- Choose the desired LED color, quantity, and characteristics (brightness, angle, current).
Power Supply Design:
- Determine the power supply type based on the LED quantity and power requirements.
- For low power, use a capacitance based power supply with an X2 capacitor
- formula: Q = CV
- where Q is charge, C is capacitance, and V is voltage).
Resistors Calculation:
- Select a series resistor 220Ω to 2.2k to limit inrush current
- Ohms Law: R = V/I
- where R is resistance, V is voltage, and I is current
Safety Measures:
- Add a parallel security resistor around 1M to facilitate capacitor discharge.
- Include a fusible resistor or fuse at the input for protection.
Rectification:
- Use a small diode bridge to rectify the reduced voltage.
LED Connection:
- LEDs are typically designed for a current of 20mA.
- Determine the capacitor value using the
- formula: C = I * Δt / ΔV
- where C is capacitance, I is current, Δt is time, and ΔV is voltage.
- LEDs can be connected in series without changing component values up to a certain quantity around 20.
- For larger quantities adjust the capacitor capacity.
Construction:
- Connect the components on a circuit board ensuring proper insulation and spacing.
- Integrate the LEDs into the chosen base or socket.
- For enhanced performance, use electrolyte to improve the source eliminating stroboscopic effects and protecting against inrush currents.
Safety Precautions:
- Emphasize safety when working with mains voltage.
- Insulate conductive parts to prevent electric shock.
- Display a warning about the lack of galvanic isolation and the associated risks.
- Builders proceed at their own risk.
Note:
- This guide provides a general overview and specific values may vary based on the chosen components.
- Always double check component ratings follow safety guidelines and consider consulting with an expert if needed.
- Building electrical devices involves risks, and caution should be exercised throughout the process.