$1200 dollar budget for 8'x4', strips or Cobs?

Im just too tech slow lol

Its ok im going to build the first half then expand on it if i like it so ill probably just use pots and timers for now.

I love the sunrise feature on my gavita though and i will figure it out eventually lol
Thanks man
Im looking into the sonoffs now

I remember that 110cm2/W from the original rule of thumb which SupraSPL once proposed. I think he was talking about total watts dissipated actually. Not just the heat. Also he kept lowering that number after he tested more.

I use 56cm Samsung F-series strips with a single row of smds @24W on 60cm of 15mmx25mmx15mm alu U-channel. The frame runs at 35C and the SMD's at 50C. With no airflow at all.

A Sonoff POW has the 16A relay and would show you how much power you gravita sucks from the wall.
Simply connect the Sonoff with the ballasts input cable and do not forget to connect the ground wires again. Download ewelink app from playstore, press the Sonoff button and wait untill it connects to you wifi router than use the app to find the Sonoff and press connect. That's it! Now you only need to program your light schedule and it works.

Im going to leave the gavita alone as it works fine
But good to know.

I got 8 to 10 weeks for the build so plenty of time to read up

wietefras said:

I remember that 110cm2/W from a very old rule of thumb which SupraSPL once proposed. I think he was talking about total watts dissipated actually. Not just the heat. Also he kept lowering that number after he tested more.

I use 56cm Samsung F-series strips with a single row of smds @24W on 60cm of 15mmx25mmx15mm alu U-channel. The frame runs at 35C and the SMD's at 50C. With no airflow at all.

Click to expand...

Yeah, it's a very old rule of thumb and comes originally from the hifi amplifier corner.
But it means heat-watt.
I've calculated a few heatsinks this way and the temps allways stays in the desired range or better. I've also assumed that the needed surface could be much lower for strips simply because of the way the heat is dissipated. A lot heat is dissipated by convection frontwise, so maybe 60-70cm²/w.
I've 1" c-channels for my strips and with my calculation they could handle twice as much wattage as I need.
Next time I'll use smaller channels or an 2-3mm aluminum sheet.

The mass of the heatsink itself is also not included in the calculation, it only refers to the required area. A heavy heatsink takes longer to heat up than a lighter one with the same surface area. So it's really just a rough estimate!

Randomblame said:

Yeah, it's a very old rule of thumb and comes originally from the hifi amplifier corner.
But it means heat-watt.
I've calculated a few heatsinks this way and the temps allways stays in the desired range or better. I've also assumed that the needed surface could be much lower for strips simply because of the way the heat is dissipated.
I've 1" c-channels for my strips and with my calculation they could handle twice as much wattage as I need.
Next time I'll use smaller channels or an 2-3mm aluminum sheet.

Click to expand...

Half sounds about right yes. My frame runs at 35C on something like 50cm2/heat W and SupraSPL also came to something like that.

I only had that rule of thumb of his in my notes, but I looked it up and I do think he's talking about all watts:
https://www.rollitup.org/t/heatsinks-for-diy-led-lamps.851907/page-5

Although it's not 100% clear. But he varies the cm2 per efficiency ranges which would not need to be if he's only considering heat watts. He also manages 60.5W from a CXB3070 and later 108W. I very much doubt he's talking only heat watts since 108W is the max rated power for a CXB3070.

Also found his later lowered rule of thumb:

SupraSPL said:

From the testing with COBs and modern LEDs, I lowered my recommendation to 25cm²/W for active cooling and 75cm²/W for passive cooling

Click to expand...

Again for total watts consumed by the COB I assume.

Randomblame said:

The mass of the heatsink itself is also not included in the calculation, it only refers to the required area. A heavy heatsink takes longer to heat up than a lighter one with the same surface area. So it's really just a rough estimate!

Click to expand...

Why would you include mass? The point is to estimate the end running temperature. How quickly that is reached is not relevant is it?

Okay, it was just an example, to show it's really just an estimate.
There are many things that affect the cooling performance. Vertical alignment, shape of the heat sink, use of additional effects to create an airflow (pin heatsinks)...
The rule itself is much older than Supra's thread...
Thanks for looking for the link. Let's see what he wrote ..?

@Randomblame , The thing I liked about those SupraSPL posts is that he did some actual testing. With some interesting finds, like how he found that more airflow doesn't always improve system efficiency.

I tried some different things with the TCI led strips myself and I found it didn't matter a whole lot for the things I tried. I tried them with and without thermal paste mounted to the aluminium. Also with and without extra aluminum on the strips altogether. I was surprised the latter made little difference.

But then, these strips run fine without any heatsink material added. So it made sense that whatever I added gave little to no improvement in thermal handling.

Guess I should experiment some with the Samsung 56cm double row strips which I still need to turn into a light. Although I'm still going for water cooling those puppies. Optimal use of the heat from the leds is something I really want to try and improve.

Yeah, he talks about dissipated watts but actually mean total watts used. His tests suggests that we actually need much less surface area than 110cm²/w. But if he talks about 60cm²/wall watt and 50% efficient COB's, that's about the same as talking about 120cm²/heat watt. Even if that only seems to be a coincidence, it does show that when we talk about heatwatt, we need about twice the surface area.
I did not have much interest to discuss about it. I just wanted to show him a safe way how can he estimate the needed heatsink size. If it is too big, no problem, the cooling will be even better in the end.

wietefras said:

@Randomblame , The thing I liked about those SupraSPL posts is that he did some actual testing. With some interesting finds, like how he found that more airflow doesn't always improve system efficiency.

I tried some different things with the TCI led strips myself and I found it didn't matter a whole lot for the things I tried. I tried them with and without thermal paste mounted to the aluminium. Also with and without extra aluminum on the strips altogether. I was surprised the latter made little difference.

But then, these strips run fine without any heatsink material added. So it made sense that whatever I added gave little to no improvement in thermal handling.

Guess I should experiment some with the Samsung 56cm double row strips which I still need to turn into a light. Although I'm still going for water cooling those puppies. Optimal use of the heat from the leds is something I really want to try and improve.

Click to expand...

Yeah, I've also interests in watercooling but it seems to make less sense with strips simply because of the low heat dissipated backwards. @mahiluana seems to have a lot of knowledge when it comes to water cooling. At least he leaves no chance out to talk about it. I asked him something today and he quickly came up with some accurate numbers, so I think he could help with the planning.

Randomblame said:

Yeah, I've also interests in watercooling but it seems to make less sense with strips simply because of the low heat dissipated backwards.

Click to expand...

I don't think that's accurate. I get the same kind of temperatures as SupraSPL got with COBs.

@mahiluana seems to have a lot of knowledge when it comes to water cooling. At least he leaves no chance out to talk about it. I asked him something today and he quickly came up with some accurate numbers, so I think he could help with the planning.

Click to expand...

I actually have him on ignore because his rants are usually inaccurate or irrelevant. He keeps droning on about the time it takes to warm up a volume of water, but that's completely irrelevant in a system like this. At least if you use some method of taking out the heat, which for me is the only reason to use water cooling.

My water cooled strips... post #50.
https://www.rollitup.org/t/sa-indoor-noob-needs-help-choosing-cobs.958852/page-3

wietefras said:

I don't think that's accurate. I get the same kind of temperatures as SupraSPL got with COBs.


I actually have him on ignore because his rants are usually inaccurate or irrelevant. He keeps droning on about the time it takes to warm up a volume of water, but that's completely irrelevant in a system like this. At least if you use some method of taking out the heat, which for me is the only reason to use water cooling.

Click to expand...

Hehe, I believe to know why...
It's because he claim 75% of the used energy is heat no matter how efficient a LED is, but you can not remove the heat from the light because it's only converted into heat when it hits a surface. Before that, the energy is part of the photons and dependent on the wavelength. If you pass the light through a layer of water, the light is also reduced and you get less growth. Seen from this point of view, the 75% rule he puts up is nonsense because its useless.
And that he heated his hot water with his LED's is of course efficient, just not everyone wants to do the same and many of us just want to remove the heat. Only if you want to achieve a specific water temperature, volume and heating time plays a role.
However, his water-cooled lamps, as far as I have seen, are quite remarkable, because well thought-out and clean realized.

Randomblame said:

I think he could help

Click to expand...

for shure - that`s why riu is made for

Randomblame said:

he leaves no chance out to talk about it

Click to expand...

yes - if you want i`m kind of a neurotic watercooler.
watercooling in the morning and watercooling in the evening
as i have my own brand and company and i do this 24/7/365
during the last 5 years.

Before i founded my company in 2013 i lived as an artist and painter for more
than 20 y in the south of europe.

So walking through the fields of led tec - i feel a little bit like Leonardo da Vinci
planing the first helicopters or war tanks.
I`m not a professional in electronics and a watercooled led lamp is just an art piece for me.

as you know - watercooled led light is not really in the focus of the lighting industries.
For many reasons, but not for the reason, that a watercooled led lamp lacks energy efficiency.
It`s just imposible to change the industries aircooled structure into a watercooled one.

A small one man company can take advantage as it is more flexible.
I guess there are only few hundred people worldwide involved in that idea
and watercooled led light is totally underestimated.....................because:

it could be one of the most important and mighty tools to combat climat change.
A solution that worldwide could substitute the fossile energy management of buildings into an electrical. Burning fossiles to produce heat and CO² --- is out !
and electr. heating with CO² absorbing green houses --- is in !!!

my calculation for my personal switch to the future is done and i can confirm:

that with an investment of 4000$ in 17m² pv panels and w. lamp system - i`m able to save
thousands of euros during the next decades --- and so it`s also a fantastic, profitable buisness
to save the world and make the U-turn in buildings energy management.

and yes - one can do all that using the self produced electricity in an electr. boiler -
but with a watercooled grow light you have the additional countervalue of weed, tomatoes or any other crop - with a 2m² (vertical) grow(in your living room?) you can harvest a good part of your personal/family consume of agricultural products. This can help to feed the world -
and so you are very welcome with your 1001 ideas and any questions. --- like everybody,
who want to move the world to a green planet.

Rahz said:

The 3000K 70CRI lamp produced slightly more but also needs to be cured a bit more than the 3500K 80CRI. Once that's done the finals will be one way or the other by about 0-1% so it's a tie.

Click to expand...

3500K 80CRI: 12.81 oz
3000K 70CRI: 12.85 oz

Highest yield/ft yet at about 73 g/swft.
GPW by output 1.8. GPW from wall, 1.7

Interestingly the GPW is only about 5% better than what I got from the Vero29g5 setup. GPPW is actually worse. There could be a variety of reasons for this so I'm not going to spend too much time thinking about it, but I think I can do a bit better with this lamp.

Done with CLU058-1825 at 1050ma. Not bad for 50w emitters.

wietefras said:

I actually have him on ignore because his rants are usually inaccurate or irrelevant.

Click to expand...

i remember that you didn`t agree with ~75% heat power production of a led chip.
i didn`t change my mind as heat production of led haven`t changed either.

i know that i can move energy efficiency - but your mind is out of reach

mahiluana said:

i remember that you didn`t agree with ~75% heat power production of a led chip.
i didn`t change my mind as heat production of led haven`t changed either.

Click to expand...

No, I would say it's 100%. Have no recollection of ever debating with someone who claimed it is some arbitrary value like 75%. Have no desire to do so either. Reading your posts again, makes me understand why I got rid of that gibberish.

i know that i can move energy efficiency - but your mind is out of reach

Click to expand...

That sounds like a Zen version of bullshit.

wietefras said:

No

Click to expand...

No problem - the world is filled up with stupid +, ignorant arrogance.
Good to know, that a dumb asshole is not able to make profit of my experience