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First time to grow, I want to buy a LED grow light

Welcome Bertsmith and best of luck to you on your first grow! Make sure you consider how much room you will have, what square footage you want to cover for how many plants and how far away you can keep your light. Like Weed Pharma says, a lot depends on your set up and how much you are trying to grow.
 
You gotta be really careful when looking for a LED grow light to buy, i would only recommend buying LED products which provide their diode chip specifications. This way you can look up the efficiency and know what your paying for.
Typically the chips advertised are run less than the advertised. For example, that meizhi grow light has 180 5w epistars, total 900watts. However they are only powered at around 2.5w at 418 watts total. The equivalent to HPS is stated at 450 watts. This suggests an efficiency not much better if at all compared to high pressure sodium.

Heres a post i made in another thread on information regarding LEDS.

Danofdanger said:
LED manufacturers use incorrect testing parameters and incorrect advertising. They are severely inconsistent compared to eachother and a lot of products offer no efficiency benefits over traditional HPS.
They advertise the spectrum, comparing it to the incorrect chlorophyll disolved in solvent charts. Completely ignoring the Mcree curve. Whats highly amusing is with a video by kind LED in which they detail the mccree curve but then completely contradict it with a chrolophyll solvent chart.

Mccree Curve

Chlorophyll Solvent Chart

LED efficiency is not stagnant, their efficiency has been developing over the years, this is called the haitz's law. Its only of the last decade that LED technology has really seen its place as the dominent light source due to lower cost and efficiency.
led-lighting-vs-hps-all-you-need-to-know-4-638.jpg


Green LED's have had poor efficiency compared to RED/BLUE. The reason behind not using green in LED grow lights is not because of plant absorption sensitivity, but because its less productive using a lower efficient spectrum LED.
Recently green LED's have now caught up, allowing its use in grow lights. Spectrum king is one of the first to adopt this and has full spectrum LED products. Knowing full well about the plants spectrum sensitivity, providing highly efficient and field tested yeild per watt.
Click to expand...
 
🌱 I never used it myself, but a friend got a ViparSpectra LED grow light and it went pretty well!🌱
 
5 watt epistar led chips don't draw 5 watts. The 5. Watt rating refers to the maximum wattage that can be be applied when wired in series. Single leds generally draw around 120 mA @ 6.3 volts.
 
As i understand it, the suggested ratings of LED diodes are a theoreticle rating based on the expectation of unpractical cooling efficiency. Array design does not effect the achievability of the rated value. Can you provide any information to clarify this ?
 
Full spectrum, white and blue 5watt epistar leds have a working voltage range of 6 to 7 volts and a maximum forward current of 700 mA.. So 7 volts x 700 mA equals 4.9 watt maximum safe operating threshold. When wired in series you cannot exceed the 700 mA rating without causing the leds to overheat above there safe operating temperature.
 
I build my led chips in an array of 4 is series and 10 in.parallel. Each series operating at 25.2 volts and drawing 580 mA.for a total of 5.8 amps total current use over the full array of 40 chips. Or 76 watts.
By running at this voltage I am well under the 700mA maximum and don't run the risk of burning out the whole panel if a led stops working.
 
All of the above-mentioned info is not always correct if using different colour spectrum chips. Red run at 2.2 to 2.4 volts and infrared work At 1.9 to 2.1 volts.
 
Why does wiring in series change the tmax of the diode chips. I would think the max forward current is unchanged no matter which configuration is used (unless tmax is changed).
Theoretically you can run the chips at the rated power (with the rated color diode) but its commonly not done as its unpractical. Iv heard with proper cooling you can even drive the chips beyond the rated values.

Yea different spectrum chips under the same wattage category run at different values, i think this is classed together just for simplicity because its too diverse to catergorise seperately.
I assume the max current rating distictions between colors is because of deficiency differences. Saying that i would expect blue to output the highest wattage because its the most efficient and releases less heat as a result, allowing it to run closer to the categorised wattage rating.
 
I'm not sure what you are referring to when you say tmax?.the maximum forward current doesn't change however you wire them up. All that changes is the current passing through each led chip. A single chip running at 6.3 volts will use 120 mA. 2 chips in series require 12.6 volts to operate at the same output using 120 mA each, for a total of 240mA, for the series.
 
This is someone else's thread and if you would like to continue this topic, it may be better to start another thread or pm me.
 
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