How to choose grow lights?


I’m building a 4 foot(L) x 4 foot(W) x 6 foot(h) grow box that I plan to grow 1-2 tomatoes and maybe 1-2 peppers (winter hobbie). I’ve got someone building me a 35red(655-660nm)/5blue(450-455nm) 1w [LED grow lights]( crecimiento-el-crecimiento-de-la-planta-de-iluminacion-led-lampara-planta-mg50w) <— like this one ) nether of us really know much about plants so I figured I better ask for help.

  1. I’ve read red/blue is the better wavelengths to get but would it hurt to mix in other wavelengths? let’s say I want toadd 30-45/1w~ white led’s.

  2. what len degree should i use? being in a small enclosed box could I just go with no len’s?

  3. Placement of lights? My plan is to have a 40x1w led as the top and 2x13+watt cfl bulb (or small 12-15 watt led) on 3 of the 4 sides.

  4. would 3w/other led’s be better?

  5. Does the PCB need a better/2ndray heatsink? It’s on a thin aluminum heatsink plate I’d say 2mm thick.


I found this to help you decide on what colours to get. LED Grow lights and here’s stuff on how light they need Plants Needs

From what I’ve read it seems like its just a bit of trial and error when it comes to grow lights, sorry I can’t be of more help. :disappointed:


vivi932015 I am sorry I say I am not going to be much use bar telling you that you need to do way more research on the topic.
Yes asking for help might have save you tail a bit.

I will give the reasons why a questions like you cannot be straight up answered. I will mention the mistakes that make the question not able to be answered.

I’ve read red/blue is the better wavelengths to get but would it hurt to mix in other wavelengths? let’s say I want toadd 30-45/1w~ white led’s.
Wavelength of light required matches to the varieties of plant your are growing yes different varieties of peppers and tomatoes have different wavelength requirements. Not having a wavelength of light the plant in fact need to grow equals malformed growth(like no flowers or fruit ever) or death of plant.

Even different times of the plants life cycle using different light colours can get different effects. Yes more plants like light in the red/blue but what they like in the red/blue can be very particular as well. If the lights you use happen to not produce some freq of light they want say hello unhappy plants.

what len degree should i use? being in a small enclosed box could I just go with no len’s?
Placement of lights? My plan is to have a 40x1w led as the top and 2x13+watt cfl bulb (or small 12-15 watt led) on 3 of the 4 sides.
Both these questions are about placement and lacking enough information to answer. Remember most plants grow straight up and down because they grow to where the most sun works out to be on average.
How reflective is box. Lens is to guide light to plant and if light reflected back from sides results can be bad in some plants same reason light coming from wrong angles too much… Putting lights down the side is a no go idea. Most cases all lighting is placed across the top when growing plants.

Lens can be worse than no len if it results in plant not getting enough light coverage. Also not having Lens can be power wasteful with light not going where you want it. How is the light fitted is another factor. Like if the in the roof is design is a reflector for the light, Resulting in lens not be required because the reflector is doing the job. Something else to remember is humidity collection. So you might be fitting a zero altering lens like a sheet of plastic to prevent moisture from plants messing with electronics. So lens or no lens is another how its your total box designed. So without total design answering one way or the other cannot be done. Yes it possible to make designs that don’t need lens but its also possible to build the complete thing and find you have stuffed it somewhere so need lens to fix your stuff up and find yourself stuffed because you have no where to mount them. So no lens is purely getting placement and reflectors right.

Do remember I don’t structurally make these so I don’t know the exact placement stuff but I do know what you need to ask the question. Like are the lights placed in reflectors at top focusing light down covering the area well or not?

would 3w/other led’s be better?
Cannot say just because a LED is a higher wattage does not mean it puts out equal light per watt. So 3 1w leds can massively out perform 1 3w led or the reverse all based on the quality of the led itself. Not enough information for anyone really to answer that question. Also you will find different wattage leds have different light mixes as well.

Does the PCB need a better/2ndray heatsink? It’s on a thin aluminum heatsink plate I’d say 2mm thick.
Cannot answer this one either because this is like how much airflow and location temperature and heatsink operational requirements question. You can make things worse at times by using a thicker heat-sink and losing airflow. The best answer to this is maybe what is basically no answer. Other thing is read spec sheet for operating temperatures and airflow requirements. Yes fitting a fans can at times be way wiser than attempting to make heat-sink thicker. Does not matter how thick a heatsink is if there is not the air flow to take the heat away.

So really I have not answered any of your questions completely. But that is kind the best you are going to get at that level of information.


I don’t have a lot of knowledge on the subject either but I do know that there is a lot of information about this in the realm of indoor cannabis growers. You could check out the Microgrowery subreddit ( Although they mainly focus on growing cannabis, there’s also a lot of info there on growing other plants and crops.


you can can find a selection of grow lights online here. This probably doesnt have the information you need but here is a good article on picking a grow light.


I’ve grown many plants in a greenhouse for years. For grow lights to be effective, they need to be on for at least 12 hours a day an you typically arrange to have them just a couple of feet maximum above the top of your plants.

To accomplish the height part, we suspend our lights on adjustable cords and raise the lights as the plants grow. Having your lights higher than a couple of feet above your plants (30" max) is a total waist of light, heat and power.

With that said and given the “gantry’s” vertical clearance requirements, grow lights are going to be next to useless, or at least highly in-effective for a farmbot as they will need to be at least 4’ above the plants so that the z-axis won’t hit them.

Also, LED lights are not quite there. Ceramic is the way to go. As always, YMMV.

  1. I heard someone say that natural sunlight is the best for plants. So I think they will be more than welcomed you to mix in other colors :)). As far as I know, the artificial light that best mimic sunlight at the moment is full-spectrum light. If you’re having troubles choosing one, check this:

  2. I think the total wattage your plants receive is what matters, not how many LED Grow Lights you have or how many watts per LED.

Sorry I can’t answer all your questions :(.


Looking for an LED grow light and still figuring out which one is for you ?

I was also confused about the same and i have found one website where they provide a complete review of the best-LED lights available in the market and they also provide the hanging distance and what not i think you guys should check it out this one It helped me to choose the led light for indoor growing!


I also faced the same problem when I’m looking for grow lights for my plant. Then I searched on google and i found this site very useful

A lot of great info mentioned on this article…


To choose best grow light for your garden, some tips may need you discuss.

Quality Build & Materials
I’m pretty sure you wouldn’t want to buy a LED grow light that wouldn’t last long. Led lights could be more expensive than fluorescent lights but LEDs should last way longer, right? So to make sure you have the best LED grow light, you should make sure built from high-quality materials.

When a LED grow light is High-quality it would be safe to say that it will last up to 10 years. US made LED grow lights are known to really have high-quality when it comes to components and production methods.

5 Best Led Grow Light: What You Need to Know About Them

Brand Reputation
When you search for LED grow lights you would notice that there are a lot of brands on the market, each of them also have some slight difference when it comes to their products.

Therefore, it could give you a hard time to decide which to pick. But remember that a good company with good reputation, a lot of good reviews and has been around for a long time has the most experiences and is more likely to have quality products.

Electricity Output & Consumption
LED grow lights would definitely be used for long hours a day, that’ll also definitely put an increase on your electricity bill.

So before picking make sure that you read its product description, make sure that you could compute the Watts and it’s still inside your budget. Take note that the higher output would compensate for any loss of wattage.

Quality Semiconductor Chip
The core of your LED light is the semiconductor chip, which also works by converting the electricity to light. But that’s not just it; it also takes part in determining wavelengths.

So that being said the best LED grow light should have a chip of at least 3 watts in order to provide the right amount of illumination.

Full Spectrum LED Lights
Generally speaking, your plants could grow under almost any type of light. For photosynthesis to be effective it would require different wavelengths.

And luckily, the best LED grow lights out there could give your plants what’s necessary throughout each growth.

Easiness of Use and Flexibility
Of course, if we’re talking about the best LED grow lights out there it’s a must that it’s flexible. Why? Because there would be a lot of times wherein you’d have to adjust your grow lights position depending on the type of plant you’re growing as well as the stage your plant is in.

A LED glow light is the best because it’ll allow you to move its placement with very minimal effort. Aside from that, you have to make sure that the intensity of the light and wavelength is also adjustable.

Warranty and Return Policy
With the normal usage of LED grow lights, they should be able to last up to 10 years, so make sure that your warranty would last longer than that.

If your warranty covers less, then it could be a sign of bad quality and worse it could be made from cheap materials. Not all but most manufacturers provide a guarantee on some parts and even include a free return shipment for some cases.


Thank you for your advice.