AC LED　&       DC LED
 The DC led requires dc adopt to drive. But AC can directly drive by AC. There are have some different parameters between AC led and DC led. Please refer to table as follows:

The option  of led work current

First The small power led(5mm straw hat) work current is less than 20mA;16mA are used. We got the work current form datasheet. What was work curve of led ?
We also give an example to illustrate the graph .in here was common φ3mm white led . the data sheet about three points on the graph.left Ordinate as resistance of photosensitive resistance（Rc）. The Abscissa as various value of led current. The graph can seen clearly that as ID increased The Rc would be depressed more lesser.
The current is smaller, the led temperature is getting smaller. This is implied by the dotted arrow in the figure. the dotted line can seen clearly that the led temperature began to pick up speed. for example led temperature reached the 40℃ when led current is 25mA.exceed 25mA were unsafe.
Base on data above , φ3mm led safe work current should be less than 25mA .

Conversion relations of led luminous flux and led power
The led luminous flux refer to how much of led luminous led source produces per unit time. In simply work is that it gives a total luminous of led. The theory has found an increasingly wide utilization in design work. . The luminous flux big ,the bright .Indicate unit as Lm, the paper below presents a kinds of algorithm for conversion between the luminous flux and led power .
In fact, we can even hear colors that the human eye cannot perceive, like infrared and ultraviolet.( infrared and ultraviolet produces by uv led strip) .but in here we talked exclusively about vision light.
The human eye in most sensitive of light is 555nm (yellow green), 1W=683lm,in other words:

1 watt can translate into 683lm. This is Calibrating Value also be the most conversion rate.

For other color, the red(650nm),1 watt equivalent of just 73lm. The reason is human eye are relatively insensitive to red.

Study on series – parallel led
There are couple of connection way for led, series and parallel respectively.
First analyses were series on led circuit ..

Advantage: Design is simply, according to led work theory All LED have the same work current . in here the work current of led equal to input current. And not , concerned about Vf, base on the scale of led power input, as long as large scale short do not occur , the led circuit would guarantee that working order. There was a litter drop in led luminous .

Disadvantage: whole led circuit is brake when a led trigger short.
the input work voltage is biggest that parallel circuit.

The follower we are talk about parallel

Advantage: the input voltage was small. Production process is simply. Without affect other led worked when a led is short.

Disadvantage: the Vf of Led have strict requirement (consistency), inconsistency of led Vf can lead current is inconsistency . in case some led current would quickly increase ,then temperature increase, All of this would be made Light decay.

The earth grounded of LED
According to new standing and request of GB7000.1/IEC60598D:
Class Ⅰ led production must be earth grounded. Strict security measures are in force in the Class Ⅰ led production.
The Class Ⅱ led production don’t need to earth grounded.
they are double insulated and approved to international safety standards.

The earth grounded of Class Ⅱ led production can’t to earth grounded.because it belong to safe ultra low voltage (SELV)

Undesirable consequences flow from Class Ⅰ led production is not value earth grounded. This has done incalculable damage, include triggle Electrostatic Induction (caused damage to led module ), electric leakage (there is a risk of electric shock).

How to value earth grounded? Please refer to pic as follows:

With some methods, current is introduced into the earth by grounded lengths of wire

Very simple, versatile modular design
No limits to the number of modules used in the ring Circuit diagram using LEDs:Circuit diagram using Lamps:

Parts:

R1 R3 R5 10K 1/4W Resistor
R2 R4 R6 470ohm 1/4W Resistor
C1 C2 C3 47uF 25V Electrolytic Capacitor
Q1 Q2 Q3 9013 NPN Transistor
Nine pcs led 20mA 3V

The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating device has its own small circuit. The diagrams show three-stage circuits for simplicity: you can add an three number of stages (shown in dashed boxes NOTE: Series Multi-level will can’t work), provided the last stage output was returned to the first stage input, as shown.

Good term between PWM and inductance to adjust led
Analog adjust led refer to adjust led luminous intensity by changing resistance .advantage: operation simply . shortcomings:The level of adjust luminous intensity is limited. In order obtain to more effect level of adjust light. We adopt inductance and PWM to adjust light. The theory as follows:

PWM through changing duty cycle to control that the conduct time of LED. The PWM can adjust multi-level led light. And inductance is energy storage component . in electrical circuit, inductance can product magnetic field when input current into inductance. The energy will release in PWM is Closure period It can not only become asset current for LED. but we need to make sure that the cycle of pwm is small than conduct time of inductance.

The relations between led current and light intensity

The LED can be produced without light For the under led forward voltage.

To Input forward voltage for LED, it will be produced light.

In an ideal status, they have the proportional relationship. But bright of led increase and temperature also increase . along with temperature increase and might damage led .

Led light theory: led light refer to Transition of electrons from the high-energy state to a low-energy state . then release by Photons(Photons have no mass — they are weightless).

The led will be light When input voltage is big than forward voltage. On the contrary the led can be produced without light.

When the voltage is big that forward voltage, the electronics quantity in high-energy state, that means current. So the current are increasing the photons will increase. But the transition rate(Quantum effects) not even be 100% . portion of current can be transition of temperature . the question of temperature could not resolve in a timely manner, it can be damage led chip. So led continuous increasing current or it not only causes led damage(base on Quantum effects).

What did The aging text box of Ultraviolet rays for?

The container is invisible until you shine an ultraviolet light on it. it’s role as follows:
Some substances are put in long hour shines by sun. they will toggle some question such as: fade, lose luster, cracked . the theory of The aging text box of Ultraviolet rays is : use uv led strip to simulate sun and use condensate water and spurted water to simulate rain and dew. Other word  with the most true of natural environment to test substance or production. Through test to analyze
that the ability of resisting oxidation and intensity . this way for improvement in performance of production. in general we gain damage information for a few years in natural environment .but It only takes a few day or a few week.

How to Measure the conduction voltage of led ?
You can Measure the conduction voltage of led with multimeter, the step as follws;
First we wanted a adjust power, and it’s series connect with resistance and LED. In here we adopt a smaller on resistance(such as 1 Ohm).now we can Measure the conduction voltage of led .two ends(NOTE: measure the voltage of led no include resistance ) . the follow we began very slowly to increase the input voltage of adjust power(the input voltage from 0 ( zero) up to) . the led luminous rapidly increased when the voltage of adjust power was gradually increase. Another phenomenon that occurs is the voltage of multimeter increase grows slowly. At moment, please take notes that voltage of LED. The record is conduction voltage of LED.