Building first LED to cover 1 sq ft grow space

[Seshwan]

Hi guys,

I am looking to build a small grow light to cover a 1sq ft grow space. Looking to use hard LED strips.

Due to space requirements I need some small length strips and beleive these should do the trick - https://www.digikey.co.uk/product-detai ... ND/6236279

5 of those will give me 6000 ish lumens per sq ft but I am struggling to work out which driver to use as I am new to this. Can you guys help me with that?

Thanks in advance!

[LEDG]

Hey there.

I'm assuming you want to run these strips at the typical drive current suggested by Bridgelux. I think the best way to do this is with a constant voltage driver.

What you'd need to do is grab a 24V CV driver and bring the voltage down to about 22V, then hook all your strips up in parallel. You would need, at minimum, an HLG-40H-24 for 5 strips, however, if you want to leave space for expansion, you could get any other 24V driver (I would highly recommend staying in the HLG series). A bigger driver will run however many strips you start with just fine, but will also allow you to upgrade in the future. I would suggest getting an "A" type driver (HLG-40H-24A rather than HLG-40H-24B), as the A type has a built in dial that allows you to set the voltage with a screwdriver. The B type requires you to wire a potentiometer.

To figure out how many of these strips you can fit on a driver, all you need to do is take the current capacity of the driver and divide it by the current draw of the strips. For example, let's say you want to run the strips at 350mA, which is what Bridgelux shows as their typical drive current. If you buy an HLG-240H-24, that driver is rated for 10A of current, so, we divide 10A by the current draw of each strip:

10/.35 = 28 strips

If you wanted to run them harder at say 500mA, you would simply dial the voltage up a little to 22.7, and on that same HLG-240H-24 you'd get:

10/.5 = 20 strips

You could also use a constant current driver and run the strips in series (or a combination of series and parallel), but myself and several other users on this forum have found that constant voltage is the way to do it. Below is the section of the EB strip data sheet I used to find the voltage at each current:

eb strips.png (46.26 KiB) Viewed 1505 times

And here is how you determine the current capacity of each driver - you'll want the 24V version of whatever size of driver you go with; just check the "rated current" specification.

240H.png (96.5 KiB) Viewed 1504 times

[Ted]

Hi guys,

I am looking to build a small grow light to cover a 1sq ft grow space. Looking to use hard LED strips.

Due to space requirements I need some small length strips and beleive these should do the trick - https://www.digikey.co.uk/product-detai ... ND/6236279

5 of those will give me 6000 ish lumens per sq ft but I am struggling to work out which driver to use as I am new to this. Can you guys help me with that?

Thanks in advance!

You could try these 1 ft samsung strips. They are the same size and about 20% more efficient than the bridgelux strips. They also run off the same voltage, so everything that LG mentioned above holds true.
https://www.digikey.com/product-detail/ ... ND/6149750

What are you trying to grow?

[Seshwan]

Really appreciate the quick responses.

You could not have explained it any better so thank you very much.

I must admit you have tempted me with the Samsungs... 181lm/W sounds so good.

How hard would it be to wire these all up as you said? I haven't really done anything like that before but I do learn quick.

[Seshwan]

Hi guys,

I am looking to build a small grow light to cover a 1sq ft grow space. Looking to use hard LED strips.

Due to space requirements I need some small length strips and beleive these should do the trick - https://www.digikey.co.uk/product-detai ... ND/6236279

5 of those will give me 6000 ish lumens per sq ft but I am struggling to work out which driver to use as I am new to this. Can you guys help me with that?

Thanks in advance!

You could try these 1 ft samsung strips. They are the same size and about 20% more efficient than the bridgelux strips. They also run off the same voltage, so everything that LG mentioned above holds true.
https://www.digikey.com/product-detail/ ... ND/6149750

What are you trying to grow?

I am trying to work out how many of these Samsung strips i would need to get close to the 6000 lm/sq ft. With the ones I linked I managed to find they they were 7.7W per strip but cannot for the life of me find the same stats for these Samsungs?

Could anyone advise on how you would work out what the wattage per strip would be? I need this to be able to work out the lm/sq ft

[LEDG]

Check out the new calculator - it’s the latest post

[Seshwan]

Thanks that worked a treat.

One thing I can;t get my head around is how parallel wiring works in terms of the driver you recommended. I am going wrong somewhere here so would appreciate you taking a look at my calculations -


5 x BXEB-L0280Z-35E1000-C-A3

Each -

22.1V
running at 350mA
7.735w

Driver -

24 VDC
40.08 W
1.67 A



40W from driver minus 7.735 x 5 = 40 W - 38.675 W = 1.325 so the strips will fit in that respect

24 VDC from driver to the 22.1V strips would blow them surely so there will be a way of reducing that?

1.67 A from driver running parallel wiring would mean it is split between each cob/connection so 1.67/5 = 0.334 so that would be running them less than 350mA, what will the impact of this be?

I was watching a Growmau5 video where he said he always wires in series as there is a risk of thermal runoff with parallel wiring? Admittedly that video was from December 2015 so has something changed where that does not apply anymore?


Thanks for taking the time to help is is greatly appreciated

[microgroaway]

I think you are just confused by the terms. The driver doesn't really consume the wattage, it just makes it accessible to DC circuitry. Each LED is what is actually drawing the power. The driver will provide as much as 40 W from your wall to send 1.67 amps @ 24V to the LED strips. So if you had 10 strips, each strip would be using 4W and 167mA. Using 5 strips each one would get 334mA and 8W. Make sense?

Edit: sorry I missed the last part of your question. Wiring in parallel is only problematic if you are only using a few strips. If one strip fails, the amperage is distributed among the rest of the strips. If you only have 2 strips in parallel, then you double the amperage (100% more) through the remaining light. If you have 5 lights in parallel, each one only gets 25% more amperage, which should be fine as long as you are not driving them too hard to begin with.

[Ted]

Thanks that worked a treat.

One thing I can;t get my head around is how parallel wiring works in terms of the driver you recommended. I am going wrong somewhere here so would appreciate you taking a look at my calculations -


5 x BXEB-L0280Z-35E1000-C-A3

Each -

22.1V
running at 350mA
7.735w

Driver -

24 VDC
40.08 W
1.67 A



40W from driver minus 7.735 x 5 = 40 W - 38.675 W = 1.325 so the strips will fit in that respect

24 VDC from driver to the 22.1V strips would blow them surely so there will be a way of reducing that?

1.67 A from driver running parallel wiring would mean it is split between each cob/connection so 1.67/5 = 0.334 so that would be running them less than 350mA, what will the impact of this be?

I was watching a Growmau5 video where he said he always wires in series as there is a risk of thermal runoff with parallel wiring? Admittedly that video was from December 2015 so has something changed where that does not apply anymore?


Thanks for taking the time to help is is greatly appreciated

I think its easier to think of it more as a give and take between the driver and the leds. With a constant voltage driver, you're telling the LED's what voltage you are supplying, and the LEDs will in turn demand a certain amount of current to run at that particular voltage. And in turn, the driver will supply whatever current the leds demand until it reaches its max. So at 22.1v, each strip will ask for 350ma of current, however at 23.3v, the current being supplied to the strip will double to 700ma.

Capture.JPG (71.68 KiB) Viewed 1425 times

The HLG A drivers have a screw on them that adjusts the voltage from 22v to 26v ~, so you can run these at the specified 22v.

Technically, the leds on the strips are wired in series and parallel, so your not really wiring them in parallel. These probably have 8 LEDs at a time wired in series to form a string, and multiple strings wired in parallel. The problem with thermal runaway is that as the LEDs heat up, their resistance goes down, and they will demand more current at the same voltage. So at 40 degrees C, your leds strip may draw 350ma at 22v, but at 70C, it may draw 500ma at 22v. That will, in turn, make the LEDs hotter, which will, in turn, draw more current, on and on and on until the whole thing explodes (joking). However, as LG has demonstrated in his QB vendetta videos, its not an issue with mid power leds wired on a PCD. COBs maybe, but you'd have to run them pretty hard.

If I were you I'd go up to the 60 or 80watt driver (hlg 60h 24A), as your right up against the 40w driver's headroom, and if you wanted to run them a little harder, you could do so,

[LEDG]

I think you are just confused by the terms. The driver doesn't really consume the wattage, it just makes it accessible to DC circuitry. Each LED is what is actually drawing the power. The driver will provide as much as 40 W from your wall to send 1.67 amps @ 24V to the LED strips. So if you had 10 strips, each strip would be using 4W and 167mA. Using 5 strips each one would get 334mA and 8W. Make sense?

Edit: sorry I missed the last part of your question. Wiring in parallel is only problematic if you are only using a few strips. If one strip fails, the amperage is distributed among the rest of the strips. If you only have 2 strips in parallel, then you double the amperage (100% more) through the remaining light. If you have 5 lights in parallel, each one only gets 25% more amperage, which should be fine as long as you are not driving them too hard to begin with.

Something I'd add is that you won't always necessarily be pulling full power from a constant voltage driver - if you set the voltage properly, you could hook up a single strip to a 600W driver and that strip won't pull all that power. It'll only take what it needs, depending on the voltage the driver is putting out.

Also, with parallel wiring, the only time you'd see the problem you mentioned (with a strip failing and the current being redistributed to the remaining strips) is if you were running parallel on a constant current driver.

If you're running parallel on a CV driver and one strip dies, nothing will change with the remaining strips. They'll keep pulling whatever power they need at whatever voltage the driver is putting out.

However, if you're running parallel on a CC driver and it's holding its current output steady, if you have one strip die, then it will force the rest of the strips to take the current that was initially used by the failed strip.