Firefly Growlight

HID vs LED

HID vs LED

HID (HPS-CMH-MH) vs LED Grow-lights

Walk into any grow or hydroponics shop and you will find a jungle of different grow light- systems. In the last few years, the rise of the LED has been spectacular and has almost replaced all other light systems. Here today, we will shed some light on the difference between the most common light fixtures: HID and LED. Hopefully you’ll gain a better understanding what makes a good light in either case.

HID – the good old stuff

HID or High Intensity Discharge growlights are characterised by a large, tube-shaped bulb attached to some sort of reflector and a ballast / driver. In some cases, the reflector and ballast are integrated, which we then call a complete fixture. There are many different shapes and types of bulbs, ballasts, and reflectors, which will not be all discussed here, however some important trends will be summarized the use.

First the bulb; the technology itself stems from two centuries ago, when the vacuum-pump was invented and oxygen inside glass-tubes could be removed and replaced by other gasses. The benefit of removing the oxygen is that hot-stuff doesn’t burn without oxygen; it can light up though. By running a high-power current through a bulb without oxygen and some sort of gas inside, a spark will ignite the gas, without it actually burning. Then a lower power current is maintained through a “filament” to keep the gas from going back to its original state and voila: we have light. As the technology was improved over time, the glass-tubes and casing were improved to decrease oxygen-leaking, the mix of gases was perfected to improve burning hours and to find different light-spectrums to broaden

Element 1; type of light

Somewhere in the 1960’s, a few companies around the world started experimenting with pressurized sodium gas and quickly thereafter the HPS or High Pressure Sodium bulb was born. This technology became dominant for nearly 50 years thereafter, with greenhouses world-wide using these bulbs. The light spectrum improved over the years from very mostly yellow-orange to include some more reds and the benefits to increase plant dry-mass immediate became apparent. Metal Halide (MH) bulbs operate in a similar fashion but use different gasses inside. Therefore, the light-spectrum is more blue then red. They can often be easily recognized because the tube has a bulge. This is done to limit the UV-radiation that MH bulbs often emit. Finally, the latest growlight bulbs are Ceramic Metal Halide or CMH, that use a different filament inside the bulb. This filament improves the longevity of the bulb as well as allows for a light- spectrum that is more all-round then both traditional HPS or MH. It is often used as a full cycle grow light, although most growers will prefer the red colours from HPS during the flowering phase to improve dry matter in the plant (harvest quantity). Most bulbs come in a Single Ended or Double Ended version, in which the latter have an improved efficiency regarding power (Watt) to output (PPF) ratio.

Spectrum of the Firefly 1000W Bulb DE

Element 2; reflector

Then the next element in the HID grow light system is the reflector. They come in many shapes and forms, but they have one main purpose: to increase the light-distribution from the bulb to the surface. If there were no reflector half the light from the bulb would shine upwards and about a quarter would shine sideways. By using a mirroring surface, the light can be focused downwards, and HID efficiency is increased about 2.5 times. Regarding the material used, aluminium seems to combine both a high level of reflection, lightweight and bendable which is all you want as a grower. The flatter the reflector, the larger the surface below the light that will be hit (although less efficient and less homogeneous). The more convex or bent the reflector; the more focus the light has on a smaller surface, which is more efficient. The latter also allows for more lights hanging from a higher surface which in turn makes it easier to work in the grow- area. Finally, sometimes you come across reflectors that are mirror like as opposed to reflectors that have so-called “drops” punched into them. Although the first one looks like it will reflect better (and looks cool), it’s not as good as the reflectors with drops. The drops diffuse the light, which makes the distribution below the light-system much better and can help avoid hot-zones.

Element 3; ballast


The last obvious part of the HID grow-light is the ballast or driver. The purpose of the ballast is to manage and regulate the current running through the bulb. As described earlier, to start up, the bulb needs a high-power current to ignite the gas inside the tube. After the light is on, it requires a different, much lower current to keep running for up to 18 hours at a time. This transformation of current needs to be done automatically by one device that is only fed one type of electricity (for example in your home it is probably something like 220-240V with 1.5A). The ancient magnetic ballast did this transformation with one big copper conductor coil. The

cooler.

Element 4; Wiring

problem with these devices is that they are relatively heavy, clunky, and noisy. Besides that, they can make lights flicker because the output isn’t always stable (like an old TV: nothing a good old bang on the side can’t fix! In reality: please don’t take this as real advise). The next thing is an electronic or digital ballast which transforms the current with several conductors on a circuit board. They are smaller, lighter, run cooler, less noisy and much more reliable (if built well) than their magnetic predecessor. They also allow for some useful upgrades; they can be applied in series, can be dimmed, can be connected to controllers, and they have self-diagnose systems. Over the years they have become more reliable, more efficient, and

The last less-obvious part of the HID grow-light is the wiring and connector materials used. These elements don’t have a very interesting history of evolution as well as not having as much impact on the light output as the first three elements discussed. However, over the years there has been a clear race to the bottom when it comes to costs and unfortunately also quality. What this means is that you can have the best light-bulb money can buy, but if the materials to connect it all together are shabby, the light output won’t be as good, but more importantly; there is a risk of over-heating, burning, short-circuits, melting, etc. Therefore, greenhouses and professionals all over the world use complete fixtures, since all the materials come from one manufacturer and are tested and approved by them. There are obviously quality differences between products offered, but as with anything: cheaper can turn out to be more expensive.

LED’s – beam me up

Somewhere in the 1920’s, a Russian scientist famously found a blinking light-effect when applying a current on a semi-conductor (silica carbide). Almost 50 years of experimenting later, the first LED’s were mass-produced as indicator lights and for remote-controllers. The only colours were red and infrared. Another 20 years later, the first blue LED’s were created by Japanese researchers (check here for the complete story). The availability of Red and Blue LED- light gave rise to the idea that plants could be grown under these lights, because of matching photosynthesis profiles. However, it took another 20 years (approximately 2014) before full spectrum LED-fixtures became available. This has to do with the invention of the “white” LED chip, which became potent enough to fully support indoor growing with only one LED-fixture. In the next bit, the different elements that make a quality LED-fixture will be discussed.

Element 1; type of LED-chip

LED’s or Light Emitting Diodes are so-called solid state chips through which a small current is ran to create a spark of light. Solid-state is important to note, because unlike other light-sources, the chip doesn’t ignite, burn, or change to a gas in order to create light. The colour of light that is emitted is determined by the used semi-conductor and the energy that runs through it. The outside case does not really influence the output colour of the led, it focuses the light like a lens and it protects the semi-conductor from dust etc. The light is therefore normally the brightest in the middle of the “dome”.

As stated before, the first LED’s that became economically attractive were infra-red and red LED’s that were mostly used as indicator lights and remote controls. The lack of power and the low availability of spectral wavelengths needed to be solved before LED’s could be incorporated into grow light fixtures. As more different ones became available and got cheaper to produce, they started being incorporated in greenhouses as support-lights for HPS systems and the sun.

Blue-emitting LED’s were the next milestone that was achieved in the 90’s. The availability of Red and Blue LED’s gave rise to a new focus within research that attempted to prove the effectiveness of these energy-saving LED’s. It seems that plants only photosynthesise red and blue light if you were to believe all the articles and tests that were published from the mid-90’s to a few years ago. However as effective LED’s promised to be in theory, no real efficient, stand-

alone growlights were constructed until halfway the last decade when White LED’s became industrially and economically available. As it turns out since then, plants also need other colours of the light-spectrum, since white light has a bit of everything in it. The problem with the first white light LED’s was that they were not particularly strong so that grow-light manufacturers had to combine a bunch of different LED-chips with added Red/Far-red in order to boost both dry-mass production. Now, the latest developments regarding white-light LED’s are that the output is boosted such that they actually can emit plenty of photons to grow plants. These so- called “sunlight-chips” contain a full-sunlight-spectrum in each LED, which often even includes some UV light. Using a LED-fixture that uses chips that each emit full-spectrum of light as opposed to using a combination of chips to emit a combined full light spectrum means that all light-colours are evenly spread throughout your grow-room. It’s really like bringing the sun into your grow room.

Element 2; the driver/ballast

Just like with HID-growlights, LED-fixtures require a different current then the one that comes straight out of your average socket. In your home, you will have either 110V (North America & Japan) or 240V (rest of the world) AC-current. Your LED will use some lower voltage, but higher Amp DC-current. Therefore, this current needs to be changed, safely, to match your light. Here’s where the driver/ballast comes in.

Depending on the quality of the materials used, the safety-measures installed and the options that drivers offer, the price-ranges may vary. The outside of the driver should be made from metal components, and it should be properly sealed to keep out dust and humidity. An IP rating of 65 or 66 will usually be sufficient to guarantee some level of protection. The inside parts are more difficult to judge, but generally keep in mind that the more reliable brands will use quality parts, although some will also have “budget/value” products.

Element 3; the wiring

Just like with HID light-fixtures, the wiring between the different elements is very important. The rubber/plastic isolation levels and thickness of the copper inside will determine how much power can safely travel through it. If this max-power is surpassed, even by peak-current, it can cause damage to the lights, electrify the isolation and the outer module of the unit, and in the worst case even cause actual fire in your grow-room.

Especially important to note is the output Amperage (Watts / Voltage output) of the driver; the higher this number, the hotter the cables can get and cause fire

IP66

if they are not top-quality. In quality LED-fixtures, you will see either very thick, sturdy cables connecting the driver to the lights or the driver will be integrated such that the connecting cables are not visible without opening up the light-fixture.

Conclusion: Get the best you can get

There are clear differences between LED and HID lights in terms of output, electricity use, spectrums, and purchase price. Those are discussed in a different article (check them out here), since there are pro’s and con’s to each light-system. At least after reading this, you will be able to understand the different lights and how they operate.

Hopefully you’ll be able to make a good purchase decision which ever type of light you choose. The most important take is: get the best quality you can afford, because both are powerful electrical devices in a competitive market. This means that there will be cutting corners in quality and safety by producers who want to offer the lowest price product (or make a better profit margin). To purchase your Firefly LED and Firefly HPS 1000W fixture in our web shop, follow this link here.