Intial project finding for computer controled grow light for science lab


I have the objective of make in a computer control grow light for my own use at home to grow saffron and for plant life here in the science lab. The problem persists with normal grow lights that the plants grow straight up then fall over. This was called online as the plants getting leggy. I want to simulate sun rise and sun set by controlling the direction of light in hydroponics. The control the direction of light by making array of LED strings control by a fet on the cathode that would control the current flow going through the light strand. So each strand could be turn to a different intensity so whole unit could control the direction of light and its intensity and thus simulate sun rise and sun set.

test of 3 led segments.
P=1.608W or 1.608 Joules per second
Assuming that all power was to generate heat.
P=0.38432 Calories per second.

Assuming 60s
E=96.48 Joules; given string is on for 60seconds.

Query to be investigated…
how much energy does the grow tent radiate. How much energy would a temperature control unit have to siphon off?

Attempts to make some control grow light.

plants getting leggy.



Roughed out idea:
Arduino Uno has 6 pwm chnls.
6 led strips arranged in circle/semi circle.
Pgm pwm chnls to fade dwn to pwr up strip to strip.
Is tent enclosed? Add pc fan at top to exhaust warm air.
Can add temp monitoring and cntrl fan w/ Uno.
Dissipating 1 (even 6 watts) watt shouldn’t be a problem.


True but this means the temperature of the tent is controlled by the temperature of the science lab. But i really want to consider my design and see how much heat i produces… Then consider either a temperature control or a revision to the project. Is this a good idea?


3 strands of length 21 inches or less a total of 1.346 Amps.

This means each LED strand is about 0.4486 Amps.
P=VI=12*0.4486=5.384 watts of energy in the strand. This is a rough reading from a power supply.

Next i am going to take the smaller LED strip and measure the resistance of the current limit resistors.
I will make a simple schematic and label the resistors and record the resistors’ value. Then try to measure the voltage drop acrossed the resistors in an active circuit. From there i should be able to calculate individual power consumption of the resistors. Summation of all power consumption of the current limiting resistor should also be able to be deduced. I will also then make the assumption all power consumed by the resistor is converted into heat. The LEDs probably also convert energy into heat but I am going to start with the resistors to see if only power dissipated resistors models the heat being produced by the circuit… This is a rough number to give me a starting assumption for my experiment. So i have guess from my model that i might check.


Pwr up one of your led strips. Let it temp stabilize. Get infrared temp reader and see how warm it gets. Think Automotive has one of these.
Do you know what the optimum temp range for the plants is?
If it needs to be cooler than its surrounding environment, you have a whole new problem to deal with.


I hear you about measuring the temperature but the ability of the environment of the grow tent affect temperature. Much like a light bulb in an easy bake oven. The more thermal mass of the inside of the tent the harder it is to heat or cool. So temperature do not describe the flow of heat. So i am trying to do more I am trying to understand the rate of thermal energy coming from the light.


In the first light strand the power consumes but the first short strand is 1.63watts The measure consumption of power of the strands current limiting resistors was found by measuring the resistance then measuring the in circuit voltage drop across the resistors. The measure power consumed by the resistors is 0.6525w… That means if the leds are 100 percent effecent the circuit is 59% at turning energy into light. Or 40 percent is being turned in heat.


I believe those are leggy because you don’t have bright enough light and the light is too red. Same thing happened to me. Then I got a full-spectrum grow light and it worked great. Ditch the fancy red/blue leds. I also use muffin fans to blow on the plants, cooling them and strengthening their stems with some motion.

Here’s the light I use… but I’m not using it now if you want to borrow it for the grow tent for a month or so.

Jump Start JSFSYS4 Modular T5 Light…


Would a regular T8 shop lamp work just as well?


I don’t know. If it did though I don’t think people would be paying what they do for T5 grow lamps.


Well before get off topic… the leggy plants where under full spectrum light that was. the timer goes on 8 hours a day then turns off. I notice your growing lettuce and this is not what i am growing. It is mid summer and i wish to grow more variety thus i need more control. I am saying i have used both led and full spectrum florescent lamps that use noble gases. I am saying direction does matter same plants grown out side do not have the same effect. I do not see how your option has any control. Could you please explain this on another thread? Perhaps you could reference the literature your using. You are probably an expert in grow lettuce but i am growing other things.


I am doing this to catalog my project. I do not find this project to have a use in patent material. I am intend to use the project in much the same way as graduate projects are posted. If i add further features that i might sell i will not post it to the community forum. So i am looking for ways to better my project and not a different direction.


I’m just sharing what happened to me when I first tried hydroponics under artificial light. I first tried many kinds of seeds…lettuce and other vegetables and flowers. They shot up 3 inches and promptly fell over. I was using a LED light that I previously used on a planted aquarium, and those aquarium plants grew well.
For my next try, I switched to the T5 lamps that were significantly brighter and it didn’t happen. That’s the only data point I can offer you.

I’ll also tell you that 10-15Watts of light isn’t even close to what you need for a 2x4’ space. You need 10x that.


And…other uses.
(You just knew someone would post something like this sooner or later). Good work!


High dollar crops justify high dollar lights!


I applaud your scientific approach and I really hope you’ll keep sharing data with us from your original research! There are a lot of opinions about grow setups on the internet and a lot of great information, but far fewer people trying different things and then sharing the results, good or bad. So I think this is a wonderful thing.

Speaking of opinions, I have a couple to share. My experience is with tomatoes mostly.

I think you should expect to have to exhaust about 100% of the energy consumed by the lights. LEDs are decently efficient at producing light (50% or so?) but even that light will still end up as heat except for the amount that the plants convert into chemical energy and I think that’s only around 1% for a daylight spectrum. So I believe that around 99% of the energy put into the lights will end up as waste heat.

I’m nearly 100% sure from your photo that those seedlings fell over from insufficient light. Either too little light or too great a distance between the light and plants. They climb ever higher in a gamble to break through the grass and find light so they can commence normal growth, and if they don’t break through within a few inches they are spent. I can’t immediately find photos of healthy saffron seedlings but the seedlings I’ve seen should not get nearly that tall before starting another pair or two of leaves.

What I’ve done is lower the light all the way down to the seedlings and incrementally move it up as they grow taller. Light intensity falls off so quickly with distance it just doesn’t seem right to waste it by leaving a gap. A thermometer placed with the plants ensures you don’t put the light so close that the plants overheat. I went all out with a light meter to collect as much interesting data as I could and I kinda hope you’ll do the same. Actually that’s how I ended up lowering the light so low. It’s one thing to know that when you halve the distance you quadruple the intensity, but seeing it happen first hand on a light meter sitting right next to the leaves I was trying to beam power into really got my attention.


If heat is a big issue, water cooling parts for computers are cheap these days on eBay and other places. Possibly mount the light strips on Aluminium brackets and water cool the brackets.

You’ll still get some radiant heat from the emitted light, but that should be much less. The waste heat from the LEDs is removable…


Sorry I understand that some people are not reputable. I do not, nor does maker space endorse the growing of any illegal plants. I am looking at control for the creation of food. For me growing plants in my apartment means a higher oxygen content. If I vent and have two cycles(Night and day) the photosynthesis produces a higher oxygen content. Is this correct?

This is lavender soaked in everclear… This the same substance given carbon dioxide and 3 hours of light. This what i grow and experiment with.