300w DIY LED components and plan in UK

[wheely]

Hi all.

Im in the UK and want to build a 300w LED grow light for a 80x80 tent. Probably using 5 LEDS.
I would like to phase out the 400watt hps.

Has anyone made a successful 300w LED grow lamp?

Would you share some ideas or plans with me please.

I hear the Cree Leds are the best at the moment. Could someone explain to me tho, why they shine white, and not red/blue like all other LED grow lights seems to look?

Also, whats best/cheapest to cool them, heat sinks or fans?

Any other suggestions for these, that are maybe in the UK, not abroad?

Are reflectors necessary?
Thanks very much for any info.

 

[Hosebomber]

Cree currently makes the best white diodes. for colored it's a toss up between a few but Phillips makes great diodes as does a few other companies. Those are red and blue. It is simply that a digital camera cannot capture that intensity correctly and the picture looks bad. They should have taken it with the diode facing a wall. You will need a heat sink regardless. If your heatsink is not big enough or efficient enough then you will need a fan.

 

[wheely]

Thanks for the reply.

So may as well just get fans then as they are about £6 each, and must be better that just heat sinks.

Do you just use White diodes, or a mixture?
I dont think its a camera problem. the cree lights when on give off white light, and other grow lights give off a mixture of blue and red lights, no?

Are 5 x 50w LEDS enough for a 80cmx80cm tent?

 

[Hosebomber]

I personally use a mixture. If it is a discrete diode it will only give of light in a 40-60nm difference of the diode. ie if it is a royal blue 455nm diode it will not give off any light above 500nm or so and 80% of the light it gives off will be between 445nm and 465nm. The mixture of red and blue is by the number of different diodes. Cree makes both discrete and white diodes. If the panel has white diodes in it they will greatly change the hue that we as humans see.

That should be enough to cover your area, but I wouldn't want to give you exact info without having the actual drive voltage and currents you will be using.

 

[wheely]

When you mean drive voltage, do you mean a Constant Voltage LED Driver?

So would you mix the 3 diodes i mentioned above together? In what formation?

 

[Hosebomber]

That driver is a constant voltage driver. It will work but I prefer constant current. As for the diodes. I would not use any of those. The ratios are not what I would choose You are basically buying 10 diodes on a single premade board.

 

[wheely]

What diodes would you recommend?
And which constant drivers? should i go for the one i posted earlier?

Many thanks.

 

[wheely]

Sorry Hosebomber, i see further up you recommended Philips for colour.

Is there an advantage disadvantage to having more lower powered leds on a panel or less higher powered leds?

Cree News: Cree Introduces the Industry?s Most Powerful SiC Schottky Diodes

 

[Hosebomber]

It depends on the grow style you are using. Most people that grow with LED use a screen of green style or keep very short plants. If you do this, there is no real need for anything over watt LEDs. 5 watt diodes are good if you plan on growing your plants a little taller. I have yet to find a need for anything over that beyond pure photon density.

 

[wheely]

Just 5 watt ones.. so do the 5w ones not need a heat sink of fan on the back of everyone, just maybe 1 fan on the whole lot. where as the high powered ones benefit from each having a cooling mechanism.
Yes i been doing screen of green.
I was thinking either 5 x 50w or 10 x 25w for the space.
The 50w crees are quite pricey, like £21-25.
But i found some CXA 1820, says 2100lw for £7.98 which i thought might be better deal, but i wasnt sure how many watts it was.

 

[Hosebomber]

Those that you listed were ten 5 watt diodes on a single PCB. The heat sink is still required even for 1 watt diodes. To find the true wattage of a diode use Vf x If = wattage. voltage times current equals watts. The CXA 1820 is a 35 watt high voltage LED.

 

[wheely]

Thanks, so would you recommend them?
I would only need 8 of this power, 35 watts (2100wl). What kind of combo?
Ive read thru your article and posts, but im still confused, sorry.

for something like this, is the heat sink the metal that the leds stick to?

 

[Hosebomber]

The diodes are good. You do not want to run them for an extended period of time at their max current (1amp).

You want 35 watts of actual draw, so you would probably want to run them at about 800mA and use 10 or so. What is more important is that you get the spectral blend correct first then adjust the diodes you need off that.

Yes the heatsink is a piece of aluminum or copper that the slug of the diode should be mounted to. It must have enough area to disapate the heat that the diodes give off from their inefficiency. This is why panels with cheaper diodes run a little hotter than those that are higher quality/more efficient.

 

[wheely]

Thanks so much. They seem like the cheapest price for the lw, without having to mount to too many leds.
So would i use a dimmer to bring them down to 800mA?
And what exactly do you mean by 35watts of draw? is that the drivers needed should be 35w?

How do i go about getting the spectral blend first? Like 2 white, 2 blue, 6 red?

 

[Hosebomber]

You can use a dimmer or the preferred method is to get a constant current driver that delivers that amount of current. A rheostat or a potentiometer can do the same thing if designed correctly.

By 35 watts of draw, I am referring to the actual draw of the diodes you are using.

Yes, the spectral blend is the ratio of discrete and white diodes you use to get the wavelengths of light in the photon density that you are looking for.

 

[wheely]

So these 35 watt diodes x 10 will actually be pulling almost as much watts as HPS?
To start out with would this be a good starting point, white x2, blue x3, red x5? to cover 80cm x 80cm.

 

[Hosebomber]

The white diodes are 35 watt max power diodes. The red and blue diodes you posted are 5 watt diodes (they actually pull about 3 watts each). For a grow area that size you will need about 225 watts of actual power draw from your diodes. Below is a basic design process flow you will need to follow:

1) Figure out what ratio of what diodes you want to use.
2) Figure out the power draw for each diode color/type running at 75-85% max current.
3) Do the math to figure out how much heat you need to displace and buy/make a heat sink that will keep your diodes from having thermal runaway.
4) Find a/multiple constant current driver/s that can deliver the needed power.
5) Go back over all of the prior steps and verify that everything is as it should be or that you have modified everything as other things have changed.
6) Create the circuitry for your diodes.
7) Solder all of your components in place and connect your driver/s.
8) Apply power for the first time and hope nothing fails catastrophically.
9) Take readings from everything and check them every 10 mins for the first hour and every hour for the next 6 hours.
10) Let the fixture run for at least 24 hours and test all of your parameters again.

If everything above goes as planned....Now you have a fixture you can use. If not go back to the set where you are having problems.

 

[dadums]

Hosebomber you have great insight and patients

 

[wheely]

Yes lots of patience man!!
When choosing diodes, should the white ones and discrete (blue/red) be of similar watts? as apposed to 5w colour and 35watt white difference.
I think i have everything to complete this project thanks to you hosebomber!
Just so understand, can i wire 2 x 25w diodes to a 50w constant current driver?
Do white,red and blue diodes all have to have the same voltage?
Power draw - is that forward current, forward voltage or power rating?

I wont ask any more questions after this as i feel ive taken enough of your time, and stating to feel a bit stupid asking all these questions. Im good at DIY, but ive realised electronics isnt my strong point.

 

[Hosebomber]

You can mix diodes of different powers, but in most cases it causes more problems. If you do the math for thermal conversion, you will have to make multiple heat sinks for the different requirements throughout the different placement of diodes. This means that you have a discontinuation of the heatsink and lowered thermal performance or you have way too much money and are using a 6" thick billet of aluminum and milling it for days to get proper performance. I guess you could always cast the heat sink, but then you lose many of the thermal properties and have to adjust the size again.... It would be much easier (and more efficient) to use the XML series of whites. This is actually some of the problem I was running into getting a manufacturer for my light. In my testing I was using Cree, Rebel ES, and a few Everlight diodes all with slightly different footprints... there isn't a company out there that is willing to go through that intensive of a production process let alone the electrical engineering that goes into it for a reasonable price. No matter how good your solder joints are, a homemade panel will never look as professional as a mass production unit.