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LED light bulb

     LED lamps (light-emitting-diode lamps) sometimes also called solid state lamps or LED lightbulbs are becoming very popular in last years. They are the economical source of light. Although their ligth flux is usually (in 2010) not equal to the incandescent bulbs or energy saving fluorescent bulbs, their advantage is very low power consumption, in most cases 0.5 - 3W. Fortunately, the power and light output of new LEDs is rapidly rising every year because they are undergoing rapid technical develompent. We can choose different colors, but probably reach for white LEDs. The white LEDs have choice between different light temperatures, from warm white imitating conventional bulbs to daylight (2700 - 10 000K). You also need to decide between point and diffuser LEDs. These choices are many types of radiation from the angle 10 ° to 150 °. Price LEDs with technical progress continues to decline, the luminous efficiency grows. Conversion of intensity to the light flux can in my online calculator.
     To power the LED bulb from the mains it is needed to create a suitable power supply or ballast. For low power and small sizes the transformer is not a good choice, therefore, is most commonly used precipitation capacity using a capacitor to AC 250V ~ best in class X2. Resistance in series (220R - 2K2) is used to limit inrush current. The capacitor is provided by a parallel security resistor around the 1M resistor, which ensure its discharge after switching off. The reduced voltage is rectified by a small diode bridge. Most of the LEDs are designed for the current 20mA, this current corresponds (in case o small number of LEDs) to around 330nF capacitor. LEDs can be connected to series of different quantity, without changing the values of components to about 20. For larger quantities of LEDs and select a larger capacity. Online calculation of the components of LED bulbs can be found below. The most common size of LED is 5mm.
     For my first LED bulb i chosen 5 pieces of cold white LED 5mm with current of 20mA and a large angle of 150°. I built it into the E27 base of the old compact fluorescent tube. These diodes have luminance only 200mcd due to the large angle .
     For the second LED bulb I chose 15pcs of 5 mm LED with a typical brightness of 15,000 mcd and an angle of 25-30°. Its maximum current is 30mA, 3.1 V drop, lifetime 100 000h. The socket is again from the E27 energy saver. Source is improved with the electrolyte. This eliminates stroboscopic effect, and also protects the LEDs from inrush currents and spikes on the mains. LEDs are provided with current of about 20mA. Light is pretty decent.

     Warning! The power supply of this LED bulb does not present the galvanical isolation. The entire circuit including the LEDs is connected to mains voltage. The conductive parts must be protected agains touch. Use a fuse or a fusible resistor at the input. You build this at your own risk. Electric shock or fire hazard.

Schematic of LED-bulbs for 230V 50Hz line with 20mA LEDs.
Schematic of LED-bulbs for 230V 50Hz line with 20mA LEDs.

The CFL base and spray cap :)
The CFL base and spray cap :)

Diffusion 5mm LEDs 200mcd 150° in their typical shape
Diffusion 5mm LEDs 200mcd 150° in their typical shape

LEDs in a cap
LEDs in a cap

Prepared for assembly
Prepared for assembly

About to close
About to close

And it shines ! :)
And it shines ! :)

lampička s LED žárovkou
Lamp with LED-bulb

LED lamp close up
LED lamp close up

It looks like this
It looks like this


The manufacturing of the LED lamp 2 begins
The manufacturing of the LED lamp 2 begins

Series-soldered LEDs in a plastic circle
Series-soldered LEDs in a plastic circle

Test of LED lamp 2
Test of LED lamp 2

About to close
About to close

Completed LED lamp 2
Completed LED lamp 2

in a light
in a light

It shines nice
It shines nice


LED lamp online calculator

The first form allows you to calculate the components of LED bulb according to desired current and number of LEDs, their voltage drop and mains parameters. The second form is the reverse calculation - calculates the current flowing through the LEDs according to the known values of the components. As well it allows to verify how much the current is affected by rounding the values calculated in first form. Enter the blue data. Red data will be calculated. The total drop of LEDs should not be larger than half of the mains amplitude (162V in case of ~ 230V mains), because LED bulb would be more sensitive to fluctuations in the mains (the mains deviation of 10% would trigger a change in LED current greater than 20%). It tells "error" when this requirement is not met or when some value is forbidden zero.



Mains voltage:   V~
Mains frequency:   Hz
LED voltage drop:   V
Desired LED current:   mA
Number of series LEDs:  
Capacity of C1:  
uF
Capacity of C2:  
uF
Voltage on C2 (has to be rated to more than this):  
V
Resistors R1 and R2 (both the same):  
ohm
 

Mains voltage:   V~
Mains frequency:   Hz
LED voltage drop:   V
Number of series LEDs:  
Capacity of C1:   uF
Resistor R1:   ohm
Resistor R2:   ohm
Current through LEDs:  
mA
 



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