The semiconductor laser is bag power laser and it wavelength is 808nm。it has great many characteristics that high power, conversion ratio of Photoelectricity is high, strongly reliability, long server time, low cost .
To understand incentive mode is best way that learning the theory of semiconductor laser。the two parallel plane mirrors formed from the cleavage facets of semiconductor, use the parallel plane mirrors as reflector. and use the mechanism of direct interband transition of semiconductor ,they formed resonant cavity . These conditions do obtain after resonant cavity is set up. then optical oscillation and feedback.

Finally they produces light radiation amplification and output laser.

LED in the development agriculture

LED in the development agriculture played an import role. fluorescent tube and high pressure sodium lamp is main artificial light source in agriculture during the past decades, How to improved efficiency(improved evenness of light source, adjust light Qualities) ? , which is the focus of current academic circles problems research. because the results showed that the light quality had a remarkable effect on the net photosynthesis of plant growth.

In recent year , the progress of photo electricity technology continuously improved that bright and light effect of light emitting diode (LED), every one most assuredly does believe in LED for development agriculture .LED has some advantage that high conversion efficiency of photo electricity , DC drive, small volume, long server time, customer wavelength and low heat . the fluorescent tube and high pressure sodium lamp is relatively backward and old compare with LED ,basically is behaved in light bright and light quality(light wavelength of proportional control can’t be achieved).

So the led is best light source fit for the development agriculture.

Electromagnetic radiation of led

Electromagnetic radiation is optical light, because light was an essentially electromagnetic radiation . the electromagnetic radiation is divide into two parts base on wavelength: visible light and invisible light. we have hear that invisible light has infrared light, uv led strip and microwave.

The 0.4～0.76μm of wavelength is better suit to animal and human .so we are call0.4～0.76μm of wavelength as visible light(short for light).more that 0.76μm call infrared light , less that 0.4μm call uv light .

the organ that can received electromagnetic radiation, we call him eyes. and the process of received electromagnetic radiation call ”seeing ”.

Relative effect of led wavelength

Human ‘ eyes seem to light of plant lamp was color temperature and lumen . the plant doesn’t take one look at color temperature and lumen during photosynthesis. the spectrum is import condition for plant growth .

the table is show spectrum that effect of plant growth280 ~ 315nm——>for process of plant form and plant physiology with minimal effect
315 ~ 400nm——>can be absorbed little by Chlorophyll, it has been try to prevent that stem elongation,
400 ~ 520nm(blue)——>the ratio of absorbing chl a and carotenoids is highest , so the plant physiology with highest effect in this range.520 ~ 610nm(green)——> the ratio of absorbing pigments is low ,   610 ~ 720nm(red) ——> the ratio of Chlorophyll is low , but these wavelength had effect for photosynthesis .
720 ~ 1000nm——> the ratio of absorbing is low, it is most exciting growth of plant cell , and effect of seed varieties germinate
＞1000nm——>is converted into heat.

We devote data table below to analysis that wavelength effect. different wavelength has different effect of photosynthesis for plant growth . we know that the from of photosynthesis needs light. the 400 ~ 720nm 400 ~ 520nm(blue) 610 ~ 720nm (red)wavelength is most of contribute for photosynthesis. the 520 ~ 610nm has low ratio of plant pigment absorbing .

Relative effect of led wavelength
Human ‘ eyes seem to light of plant lamp was color temperature and lumen . the plant doesn’t take one look at color temperature and lumen during photosynthesis. the spectrum is import condition for plant growth .

the table is show spectrum that effect of plant growth:

280 ~ 315nm——>for process of plant form and plant physiology with minimal effect
315 ~ 400nm——>can be absorbed little by Chlorophyll, it has been try to prevent that stem elongation,
400 ~ 520nm(blue)——>the ratio of absorbing chl a and carotenoids is highest , so the plant physiology with highest effect in this range.520 ~ 610nm(green)——> the ratio of absorbing pigments is low ,    610 ~ 720nm(red) ——> the ratio of Chlorophyll is low , but these wavelength had effect for photosynthesis .
720 ~ 1000nm——> the ratio of absorbing is low, it is most exciting growth of plant cell , and effect of seed varieties germinate
＞1000nm——>is converted into heat.

diy led grow light

1: Buy some plant led : several of red light led (10 pcs is best) and two pieces blue led .

2：Prepay some wire、Screw、 nut、one strip Aluminium alloy pipe

3：Prepay a power supply,

4：Prepare some tool, just like: Hacksaw, stripping pliers, pistol drill, electric iron

5：Okey start our DIY work.

Application range of LED drive IC

The led drive IC has wide applied space for design of led electricity circuit. in present led market ,it can divided into three kind:

first class, for consumer electricity production. these kinds of application features is that will drive the electricity circuit by using the battery .in generally , the scope of drive voltage is form 4.2V~8.4V, so this drive IC aims to promote the low voltage of LED usage .

second class, for vehicle lighting. because the input voltage is vehicle battery ,so the voltage scope is 12V~48V,buck led ic many opportunities to use it.

three class, for Architectural decorative lighting or home lighting, AC transform to DC is necessary for this kind drive IC. the main function of drive ic circuits is to convert AC currently to constant DC currently.

LED lighting device

LED lighting device divide into low power（IF=15-20mA）and high power （IF>200mA）base on led power. the low power led generally use in led Fluorescent lamp, decorative lamp, grille lamp; and the high power led that can be use for Household lighting lamp, spotlight, underwater lamp, wall washing lamp, street lamp, tunnel lamp, automobile work lamp.
The led lighting device if device of low voltage and big current . so the currently of led was decide that led luminous intensity. if this is the case , the input currently are to strong will effect  the led luminous attenuation. the input currently are to small that would interfere with led luminous intensity.
In summary , the electricity designer chose that led constant currently source to drive LED which we considered right.

LED drive technology

There have two way to drive that led, may divide into resister currently limiter and constant current.

The resister limit current is one way of drive technology. the led has advantage of design simply and low cost . but it has a lot shortcoming:
*the current will change along with differ input voltage or forward voltage. for this result ，the indeterminateness of the led light produced by differ input voltage.
*the low efficiency: the drive efficiency are generally very low on high battery voltage drop. the reason for this is that most of power consumed in resister. the acquisition of heat is certainly result. so the dispel heat is big problem for resister currently limiter.

Other way is constant current source . is has advantage of current constant. but the price of constant current source is high than resister currently limiter.