Chapter 3 LED Lights

Question 1

What is a LED????????

LEDs differ from HID lamps in that they use a ___________ ____________to produce light instead of creating light from hot, glowing gas plasma.

Answer 1

LED is an acronym for light emitting diode.

Semiconductor diode

Question 2

When an _______________________is passed through an LED, a tiny chunk of material at the center of the emitter called a “_______”glows a particular color depending on the material it’s made from.

Answer 2

ELECTRIC CURRENT

DIE

Question 3

The die sits in a reflective cup to direct the light outward through an affixed ______________lens, and then the entire thing is enclosed in an ________________case.

Answer 3

EPOXY

EPOXY

Question 4

A grow light made with LEDs consists of 5 components:
\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_
\_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 4

Emitters
Heat Sink
Drivers
Cooling Fans
Housing

Question 5

Individual emitters are connected to the ________________, which along with cooling fans disperses the __________the LEDs generate.

Answer 5

Heat Sink

Heat

Question 6

The light’s driver, analogous to a _______________ in HID lighting, provides _____________to the emitters

Answer 6

Ballast

Power

Question 7

In newer-generation LED grow lights, the emitters are topped with ___________ ____________ to focus and intensify their light.

With LEDs we can control the exact __________________of light that reach our plants instead of adapting our gardening methods to what’s available. We can create plant-specific lights that are efficient for growing a particular crop.

Answer 7

Secondary optics

Wavelengths

Question 8

3 key “stand-out qualities of LED grow lights:

________________

________________

________________

Answer 8

Less Heat

New Spectra Not Available Under HID

“Tunable” Lights

Question 9

LED grow lights produce ___________heat than HIDs.

What happens when the light is switched off? The photons of light _____________________but what happens to them?

Answer 9

Less

Cease to exist

Question 10

Physics tells us that photons “___________” into the “system,” which in this case is the grow room. This phenomenon is described in the theory of ______________________which states that energy cannot be created or destroyed—it can only be converted form one form to another.

This is a long way of saying that when light decays, it ultimately becomes ___________________.

Answer 10

Decay

Conservation of energy

Heat

Question 11

1 watt of electricity equals ______________________of heat.

This is completely true for all light sources—HID lamp, fluorescent light, LED, or any other light source.

Answer 11

3.412 British Thermal Units (BTU).

Question 12

Why do LEDs produce less heat? It’s simple: with LED grow lights, most gardeners use ________________ —somewhere between 50% to 60% of HID _____________. Less __________equals less heat.

Answer 12

Less watts

watts.

watts.

Question 13

Infrared heaters work by heating ______________________which in turn heat the surrounding air. This is the opposite of traditional heaters where they heat the air then the air warms the surfaces. Keep in mind that in your garden, those surfaces being heated are your plants’ leaves and stems!

Answer 13

exposed surfaces

Question 14

An additional reason LEDs produce less heat is that HID lamps, especially HPS lamps, produce a lot of waste heat in the _______________________of the light spectrum.

Answer 14

infrared (IR) region

Question 15

If lamp manufacturers published ________________________charts that went beyond the typical end point of _______________, it would be easier to understand where this extra IR heat energy comes from.

SPD charts that go up to at least________________ would provide a way to compare some of the heat generated by different light sources.

Answer 15

spectral power distribution

750nm

900nm

Question 16

chart below shows that HPS lights generate large peaks around ________________which is all IR heat—quite a lot, in fact, compared to the PAR light emitted.

Answer 16

810nm-plus,

Question 17

best things about LED grow lights is the ability to control the _____________________your plants receive.

Want more blue? If your light allows it, add more blue emitters. If not, supplement with an all-blue LED fixture. If you want more red, add it. Many LED grow light manufacturers will accept special orders for grow lights with custom spectrum colors.

Answer 17

specific light energy

Question 18

“Tunable” Lights:
Some LED grow lights offer a ____________________which allow all of the reds or blues to be turned up or down together on separate knobs.

Some growers believe that turning down the reds shortens the ___________________distance on plants—the vertical stem height between the flower or leaf sites.

Answer 18

Tunable spectrum

Internodal

Question 19

For years, gardening “best practices” have held that internodal distances are best kept short by placing the light at the proper height and not making the plants “_____________”for a light that is positioned too high.
This holds true for LED grow lights.

Answer 19

Reach

Question 20

These multi-adjustable lights will help unlock the spectrum secrets of many plants and will likely lead to the development of __________________ LED grow lights.

Answer 20

plant-or strain-specific

Question 21

LED grow lights are typically positioned within _______________above the plants, while HID lamps are 18 to 36 inches above plants, saving another 12 to 18 inches.

Answer 21

6 to 18 inches

Question 22

Rblue, and green are the primary colors of light;

Answer 22

Red, blue, and green