DIY leds Discussion Thread for all your how tos and doubts and anything related

[Ca++]

Seems strange to use 930, if it were only for heating. Making 930 light, is a loss of heating efficiency. When judged beside a typical hot body radiator.

I tried a ceramic reptile lamp. They look like an R50 spot lamp, but black. You can see the element, shaped like an old hob that was good for knives. Like many 220v buyers, it got so hot it made some visible light, and died. The incandescent lamp seems better, but watch halogens if it's heat on your mind. They are more efficient than standard tungsten lamps, because they make less IR. This trickery also takes away from the smooth graph curve of a normal lamp. Though I still found they did the trick.

 

[Neferhotep]

If these can achieve high enough leaf temps then I can remove my heater.

I doubt it. Plants will have to evaporate water. That takes 2256 kJ/kg.
It's plain physics and math. If your plants evaporate 10 kg water per day, you can calculate how much energy that takes. If you have only LEDs, the LEDs will have to provide that energy and it's a LOT of energy.

Let's say 9 kg during lights-on and 1 kg during lights-off.
9 kg => 20304 kJ
J = Ws
20304 kJ in 12 hours
20304 kWs / (12 × 3600) s = 0.47 kW

So for evaporation only you'll need 470 watt continuous.

To counter this problem my idea is to use an air to air heat exchanger. Warm up incoming air with exhaust air. But that's another topic.

 

[Aristoned]

I doubt it. Plants will have to evaporate water. That takes 2256 kJ/kg.
It's plain physics and math. If your plants evaporate 10 kg water per day, you can calculate how much energy that takes. If you have only LEDs, the LEDs will have to provide that energy and it's a LOT of energy.

Let's say 9 kg during lights-on and 1 kg during lights-off.
9 kg => 20304 kJ
J = Ws
20304 kJ in 12 hours
20304 kWs / (12 × 3600) s = 0.47 kW

So for evaporation only you'll need 470 watt continuous.

To counter this problem my idea is to use an air to air heat exchanger. Warm up incoming air with exhaust air. But that's another topic.

I’m using 750-1,500W of heater right now.

Turning the heat up in the whole place to ~78° F helps maintain temperature. In deep winter the 1,500W heater will be running non-stop. If I can get IR to do that at half the operational cost?

Sure!

 

[Neferhotep]

The idea I find very neat. Provide energy the same way the sun does. But in nature these plants grow when it's warm. In your room you have to exchange the air and thus you are sucking in cold air all the time. To counter the cold air inflow you want to provide radiation. That needs lots of radiation and I think the plants will suffer.
But go ahead, no guts no glory

I’m using 750-1,500W of heater right now.

You need a heat exchanger

 

[Aristoned]

The idea I find very neat. Provide energy the same way the sun does. But in nature these plants grow when it's warm. In your room you have to exchange the air and thus you are sucking in cold air all the time. To counter the cold air inflow you want to provide radiation. That needs lots of radiation and I think the plants will suffer.
But go ahead, no guts no glory


You need a heat exchanger

The whole place was turned up to 78° last night to reduce heater cycles. I was hoping I didn’t have to run the whole place so hot, I like it colder. I may just get a larger humidifier and just condition the environment before the tents draws in the atmosphere.

For now, I’m holding consistent temperature and humidity. 84°/70% lights-on and 70°/60% lights-out.

Cheers!

 

[Drop That Sound]

i had 72 14-watt bulbs or 1008 watts over a 54" x 54" or 20.25 sq ft canopy for 49.77 watts per sq ft during the veg and stretch phases

and 66 14-watt 2700k bulbs and 150 watts of incandescent for a total of 1074 watts over the same sq ft in flower for 53.03 watts per sq ft.

the incandescents were in the form of 6 25-watt bulbs spread evenly over the canopy. this eliminated a single hot spot caused by one big bulb and kept the height about the same as the leds above the canopy.

room temperature was maintained at 82-84f lights on and 74-76f lights off.

i don't have the equipment to measure infrared. i do have a good par meter. i have a spectrum industries light scout. a 375 dollar instrument that functions on a par (lol) with the apogee meters.

in the last 5 years i have tried every ratio of white light that can be achieved with 2700k and 5000k bulbs. and did not get these results.

I recently made a 24 bulb SIL fixture, and been wondering what to supplement it with. I was gonna use a couple 4' long t-5s as part of the actual frame (possibly along with arcadia reptile UVB HO bulbs installed), to hold my bars with the lamp sockets together as one whole fixture, but ended up just using some lightweight alum angle instead..
Been thinking about adding low wattage halogens just like you've done! I have 15 squares in between the 24 bulbs grid and figured I would go with 15x 10w G4 halogen bulbs (instead of the 25w versions).. So yeah, 150w too (over roughly a 3.5 x 4.5' area), but a little more spread out evenly, with one 10w mini halogen centered perfectly between the 24 SIL bulbs.. I wanted to ask if you think I should get the bare bulbs, or spend more for the reflective domed kind? They have 20 packs of bares for a good deal, but the reflector ones cost way more..
Also, I can just get 20, 25s or even 50w, and use less current as if I'm dimming them right? Down to ten watts or whatever.. Got me thinking, I might as well go with 25s, and have the capability of boosting them all up really high (like, over 300w!) if I go with a beefy enough PSU.

 

[Rocket Soul]

I doubt it. Plants will have to evaporate water. That takes 2256 kJ/kg.
It's plain physics and math. If your plants evaporate 10 kg water per day, you can calculate how much energy that takes. If you have only LEDs, the LEDs will have to provide that energy and it's a LOT of energy.

Let's say 9 kg during lights-on and 1 kg during lights-off.
9 kg => 20304 kJ
J = Ws
20304 kJ in 12 hours
20304 kWs / (12 × 3600) s = 0.47 kW

So for evaporation only you'll need 470 watt continuous.

To counter this problem my idea is to use an air to air heat exchanger. Warm up incoming air with exhaust air. But that's another topic.

I generally like the data driven approaches but are you completely sure that this is what it would work out like in practice? You can increase transpiration with simple airmovement; plants will transpire more when in a bit of wind than in still air. The only energy added in this case would be some fans. Im not saying youre wrong but id like to see how these things work out in a practical scenario before id bite.

Thermodynamics is deceptively easy and straight forwards in theory but some of the most complex maths when you try to take it into practice. And there are some cases where the easy maths just seems to get contradicted by real life data. If you back to ye olden days youll find a fair few references to people saying their 1000w MH heats their space more than their 1000w hps. Which shouldnt make any sense if you apply the standard maths yet it still seems to happen in real life (though im ling removed from both HPS and MH so its hard for me to do practical tests).

The one thing i do know is that these thermodynamics arguments tend to provoke the biggest arguments online. Its like it sets off two sides of thinking against eachother: on the one side the rationalists who touts a rules based world with predictably on the other side the empiricist, who rely on observation and argue that all and any of the rules we base or calculations on is and has to be based on empirical observation; which is also true. Whenever thermodynamics looks too easy i start to suspect that there is something missing before im prepared to trust 100% that what comes out of the math is actually what we will see in reality.

 

[Neferhotep]

Are you saying that evaporating 9 kg of water doesn't need 20304 kJ?

1000w MH heats their space more than their 1000w hps

There should be a reason for that.

 

[Rocket Soul]

Are you saying that evaporating 9 kg of water doesn't need 20304 kJ?

No. Im saying have you tried this out in practice? Versus just increasing airflow around the plants.

 

[Neferhotep]

Airflow in general should increase evaporation and as a result of that lower the temperature.
I never measured any of this specifically.

But the idea is that an air heater isn't necessary if you shine enough infrared on the plants. I doubt that would work but as I said, no guts no glory. Check it out.

 

[Rocket Soul]

I dont really wanna argue about this by point, as ive said its one of the messiest arguments i see repeatedly over forum threads and the best way to derail a good and rewarding convo. My point is that the user expenditure of energy may vary depending on approach (heaters, HID, fans) to achieve the same amount of effect (increased transpiration). The basic energy expenditure in the scale of physics would of course remain the same but how efficiently we achieve this depends on which way one goes to get the energy where it is needed. And that to gauge which way works the best from a user perspective my advice is to run practical tests and measurements instead of just doing it in an all maths based approach. Chances are that the math wont math with reality cause its very hard to do thermodynamic calculations on a dynamic system; there are always things that tend to be overlooked when trying to bring the theory to practice. Im no saying i dont believe in the science, im saying its complicated to apply it and one should start in both ends if trying to get a system running: both by predicting thru maths but also from looking at data coming back from measurements.

 

[Neferhotep]

to achieve the same amount of effect (increased transpiration).

Not only transpiration; also metabolism to make use of the dissolved elements.
Increased transpiration is worthless if the plant cannot use the nutrition.

 

[Aristoned]

Are you saying that evaporating 9 kg of water doesn't need 20304 kJ?

There should be a reason for that.

I’d estimate that the red colour would carry less heat than a white colour.

This may be contradictory to what we believe since we usually see fire as red and not white.

 

[Aristoned]

Airflow in general should increase evaporation and as a result of that lower the temperature.
I never measured any of this specifically.

But the idea is that an air heater isn't necessary if you shine enough infrared on the plants. I doubt that would work but as I said, no guts no glory. Check it out.

I dont really wanna argue about this by point, as ive said its one of the messiest arguments i see repeatedly over forum threads and the best way to derail a good and rewarding convo. My point is that the user expenditure of energy may vary depending on approach (heaters, HID, fans) to achieve the same amount of effect (increased transpiration). The basic energy expenditure in the scale of physics would of course remain the same but how efficiently we achieve this depends on which way one goes to get the energy where it is needed. And that to gauge which way works the best from a user perspective my advice is to run practical tests and measurements instead of just doing it in an all maths based approach. Chances are that the math wont math with reality cause its very hard to do thermodynamic calculations on a dynamic system; there are always things that tend to be overlooked when trying to bring the theory to practice. Im no saying i dont believe in the science, im saying its complicated to apply it and one should start in both ends if trying to get a system running: both by predicting thru maths but also from looking at data coming back from measurements.

I was hoping this could be tested to see which hypothesis would be accurate.

Shoot.

We all might be wrong.

 

[Rocket Soul]

I suggest someone threads the discussion for a separate thread as we are getting off track about diy led a bit. Or just go on here for whatever its worth

Found this which could be a good primer for any discussion.

Take away: at same airtemps (20C) vpd doubled when raising leaf temps fron 18C to 22, a mere 4 degrees. My guess is that IR will change transpiration a lot more than we think. Im not very sure of how much IR is needed for this though.

Edit: i dont have a grow room to test this out in but anyone who want to try it: get a low watt halogen spot light with a tight beam angle and hang it above a plant in a grow where plants drinking roughly the same speed. try to evaluate the difference in drying time between the halogen supplemented and rest of the plants having recently watered with same amount of water. Not super scientific but its the best i could think of

 

[Neferhotep]

get a low watt halogen spot

... and drive it lower than rated voltage. It will emit more infrared.