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This post goes over first go-round of a hydroponics system that is using a DIY LED setup.

I started with a basic DWC system in our basement that used one T5 bulb for lighting.

DIYDWCSystem

As noted in this post, the LUX was 9950.  I started measuring the  KWH with a Kill-A-Watt and found the TD5  bulb used 1.15 KWH.  The PAR value was 100 µmol photons m2s-1

The T5 provided 9950 LUX.  It will be interesting to see how the LED system compares relative to its PAR and LUX values.

Since then, I have found that I am lazier than I thought.  I want the plants within an area I frequent regularly.  That would be the kitchen.  Many years ago we redid our kitchen to include an eating area with a big round table which has hand, footprints, and drawings done by our kids when they were little.  Luckily we love our home with no plans of selling.   We had plants surrounding the area behind the seats.  Unfortunately, our two cats delighted in using the dirt as a cat box so we removed the plants and covered it up.  I’ve decided to reopen this area to a hydroponics system that surrounds the back.  What is nice about the hydroponics system is it is all water.  I can keep the cats out of the system, and I’ll figure out how to keep one of them from eating the leaves and puking them up.  He likes to do that.  

Since I like to get hands-on, I’ll be adding and adjusting constantly as I explore the “best” way to grow vegetables that we can pick to make a fresh salad or have a snack.

My initial start is what I refer to as my “Basic Hydroponics System.”  Disclaimer: I am just starting on my journey into hydroponics.  I do not claim my setup would work well for anyone else.  I am hoping it provides some knowledge to a fellow n00b and hopefully those more versed in this area will let me know what could be better.

The Base of my Hydroponics System

I’m going to start by growing tomatoes, cucumbers, spinach, and dwarf sugar snap peas.  I picked these because they are some of my favorite vegetables.  They also struck me as a fairly diverse group.  I thought a diverse group would give me a wider range of results given my early stages in hydroponics using LEDs as the light source.

To start with, my indoor garden includes two 5 gallon buckets purchased from Lowes each for under $3. I also got two bucket lids  at $1.28 each.  

In one I put a 6″ net pot.  I bought a 10 pack for $21.  Assuming I’ll use them all, the one 6″ net pot cost $2.10.  I put three 3 inch net pots in the other bucket.  The 3 inch net pots cost $6.50 for 1 dozen.  THe cost for three was $1.63.  I got a pump + hose + airstone from petco for $13.  I filled the net pots with ““Easy Green Hydroton Growing Media, 10 Liter Bag” ”  (aerated clay pellets).  The bag cost around $25 making me think there must be a less expensive alternative – like gravel or something that people try to get rid of.  Something I need to look into.

I put a  rock wool cube ($12.84 for a pack of 45 – $.29 each).  There are other options that might be better such as perlite or coir.  Another area where I need to know more about.  I chose rock wool because it was used in the DIY article I started with. 

What About the Temperature?

Water Temperature

 
I wasn’t sure what water temperature would work best for the vegetables.  Google searches (at least with the search terms I was using) did not lead to any additional knowledge, so I asked the question on the hydro subreddit and got this information:
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[–]ElWaffles 4 points 1 day ago

Ideal water temp should be 68 up to like 72. 80f is no good for holding oxygen.

 

[–]thewsPlant Eater 2 points 1 day ago

For water you normally want to keep it under 72F no matter what if you can.

Air temps don’t matter as much, but they can’t stand full sun and temps in the summer (90F+ heat). Of course they don’t like under 40F temps very much either, and they don’t do very well with short days (supplemental light if in a greenhouse in the winter).

 

–]Potatonet 1 point 14 hours ago

Hi,

During veg to early fruit set: 70-78 During mid-late fruiting: 75- low eighties

The tomatoes need the heat for proper sugar conversion and flavor, especially in a hydro situation, no one likes a water ball.

 

[–]squarepush3r 0 points 1 day

air temperature range ideally 55-80 range

water temp from 55-80 as well

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 Given these answers, my current thoughts is to keep the water at about 72F/22C.  Before I automate and to compare the sensors that are used to hand held units, I also got a digital thermometer.  The current temperature of the water is 62F/17C.  Since this is a little lower than I want, I went ahead and ordered two submersible heaters whose temperatures can be adjusted.
 

Air Temperature 

The Dance Between PAR and Air Temperature

 
I just read an interesting research paper (Tomato quality is more dependent on temperature than on photosynthetically active radiation) that concluded air temperature is more important than a higher PAR value.   This image is interesting.  The researchers plotted the different quality characteristics of a tomato relative to a Control group (where Control means 100% PAR values).  The 70% and 50% PAR values reference the samples that were considered in shade.  What is shown here is the tomatoes in the shade did not have readings that were very different from those in the sun.  
 
Sun Ray 1
SSC can be interpreted as sugar content.  The sweeter the better! 
 
Based on the results summarized in the above image, the report concludes “growers in our region could obtain tomatoes of similar quality under lower PAR than natural sunlight.
 
Now that PAR value has been discounted, the researchers looked at tomato qualities based on temperature ranges.  850C is the cumulative degrees measured over 45 days.  Dividing the numbers by 45, 850C = 18.8C/66F and 1000C = 22.22C/72F
 
Sun Ray 2
 The paper notes (wow! learning new words like organoleptic!) Regarding organoleptic properties, all parameters showed slightly lower values at the lowest T cum  interval  (T cum < 850◦ C) (Fig. 7). It was concluded that daily T cum has an effect on tomato quality, with lower values of T cum leading to higher and lower values of antioxidant and organoleptic properties respectively.  They seemed to discount the variation in Vitamin C based on a comparison of mixed results by other researchers.  Having my background in science leads me to think any of these results can be reasonably disputed but they are a stepping stone to a great knowledge of how temperature and PAR values effect tomatoes during their flowering stage.
 
Although they found yield had a quite different outcome.  Lowering the PAR value by 30% from sunlight decreased the yield by 14.3% and a 50% lowering decreased the yield by 38.1%.  Also, fruit size decreased as the PAR value lowered to 50% of sunlight.
 
I have found over the years that there is research can’t help itself but by being subjective.  It is not the data, however the interpretation.  With that said, as I build up my knowledge base, I’ll follow some of the findings.  I view the settings of the hydroponic system(s) as an iterative process.
 
Thus based on the results of this article and given I am mostly interested on the organoleptic 🙂 qualities, as with the water temperature, I will maintain a constant 72F air temperature using the space heater noted earlier in the CoGs for the base system.  The space heater will be too small as the amount of plants grow. For now I’ll be able to gauge results on a smaller amount of plants at the lowest possible cost.
 
I will not raise the PAR values for this setup.  I will do another LED setup that emits higher PAR values.

The Food

 

To start out with, I am using Dyna-Gro – Grow 7-9-5 Plant Food.  I chose it because It was recommended on a DIY Hydroponics blog posting, it got good reviews on Amazon.com (note to self: be more skeptical about reviews!), and it advertises itself as a nutrient supplier that spanned the vegetation and flowering cycles. I’ll see how well it works and then change as I see what works and learn from others.  

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Note:

The 7-9-5 refers to the percentage of Nitrogen-Phosphorous-Potassium.  I’ll most likely change the nutrient mix once I evolve my learning on the appropriate nutrients for the plant and plant cycle.

 

 A thread on the hydro subreddit had some advice on what this expert uses:

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uranium_hexanitrate 3 points 7 hours ago

Start with clarifying your NPK: 13-11-9. You want the nitrogen for vegetative growth, and while 13 is a bit on the low side, it’s certainly more than adequate. Many people will use a balanced fertilizer (10-10-10 or 20-20-20) and still get good results, so super-high nitrogen need not be applied.

Back off on nitrogen and up the phosphorus and potassium for blooming. Peppers aren’t picky; you can probably make do with the same formulation all the way.

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As noted here:

In hydroponics, the plant roots are constantly provided with all the water, oxygen and nutrients they need….As a general rule, a plant consumes more nitrogen during the formative or vegetative stage, and more phosphorus, potassium and magnesium as it flowers. Throughout its growth cycle, the plant will also consume calcium, sulfur and micro nutrients such as iron, manganese, boron, molybdenum and copper.”    

Nutrients

(image from here)

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Measuring nutrient levels

There are two measurements that are important to stay on top of – the pH value and theEC/TDS/PPM  value of the water the plant roots call home.

Measuring PPM

I bought this inexpensive TDS Tester.  It seems to work pretty well.  Also, it seemed that several on the hydro subreddit used this tester with success.  The first reading I got before adding Dyna-Gro was 50 ppm.  I added 100ml to each 5 gallon bucket.  The new ppm reading is 1540 ppm.  According to the information found here, 1540 ppm seems like an acceptable value.  Like everything else, I’ll adjust as I learn more. 

Measuring pH

Maintaining the right pH level is important to how well the plant can absorb nutrients.  I found this image to be helpful:

PH Values

 

I used a PH Meter to measure the pH.  It turns out the pH was too basic at 7.  I ordered General Hydroponics pH Down to get the pH around 6.  (FOLLOW UP: Do NOT use this pH meter! I discuss this in an “Indoor Garden Report.”

There are many different products that can be used to measure the pH value.

 

Pieces of the Base System

 

 Lowes Bucket  LowesLid  RockWoolCube  NetPot  ClayPellets  Digital Thermometer  WarmWave Space Heater  dyna grow nutrients TDS EZ  PH Down  3 in 1 meter

Bucket

Lid

Rockwool cube

Net pots

Clay pellets

Submersible thermometer   Space Heater Nutrients  TDS Tester  pH Down  pH meter

 

 Cost of Goods

All dollar amounts are pre-tax.

Shared

Per System

 
 

 

1 6” Net Pot

3 3” Net Pots

Bucket

$2.78

$2.78

Bucket Lid

$1.29

$1.29

Net Pot(s)

$2.10

$1.63

Rock wool

$0.29

$0.87

Clay pellets

$1.55

$0.72

Air pump, etc.

$12.99

$12.99

Submersible Heater

$18.28

$18.28

Total

$39.28

$38.56

 

The LED Setup

I went over the components I would use in my first LED system in this post.  My husband and his friend built me a fixture from sheet metal they had lying around then mounted the CPU heat sinks on the fixture.  I put one LED array (cool white) on one heat sink and the other warm white on the other heat sink.

I set up this LED circuit:

2LEDCircuit 2

 
 

 

 

 LDDCircuit  power supply  LEDs  LEDsOnPlants  Crimp On Spades  CPUFan
 
I used spade terminals to attach the wires to the power supply.  I got these at Home Depot.  The smallest amount I could be in this size and type was 75 for $6.97.   I used 5.  Plenty more are left for future projects.
 
As the hours past, the heat sinks rose to a temperature in the mid-90F.  The steel plates got into the mid-80’sF.  I mounted each LED on a CPU cooler.  These acted as very nice heat sinks.  They both have a fan.  So I powered them up with a 12V wall wart.
 
superAngryGuy had a great posting in the hydro subreddit on the amount of LUX a plant should get:

15000-20000 lux____ the lower end of what we want for veg growth

35000-40000 lux____ what we want to try to hit for flowering

75000 or so lux_____ it’s pointless to go beyond this level of light intensity, saturation level
 
 During this past summer, I measured the outdoor PAR value in mid-August on a day that had a few puffy clouds as well as the PAR value for the T5 light I had previously been using.  The measurements were:

Outside – Sun

1865 µmolphotonsm2s-1

Outside – Shade

170µmol photons m2s-1

T5

100µmol photons m2s-1

 
 

 1 Bucket PAR and LUC  3 Bucket LUX and PAR
 
 
 
 
I was going to add an Arduino + RF so that I could control the PWM/DIM in order to lower the brightness of the light.  This is easy to do since as you can see in the image each LDD has a DIM pin.   For now I’ll stay with what I have here and won’t use a dimmer since full daylight lux is around 10,000 – 25,000 LUX and direct sunlight is between 32,000 and 130,000 LUX.  Although both superAngryGuy’s and the wikipedia entry on LUX point to direct sunlight for flowering tomatoes. 
 
Given the outside sun PAR value, I am concerned the PAR values on the plants are too low.  They are however much higher than outside-shade and the T5.   Down the road I’m sure I’ll be adjusting the LED setup.
 

 

 

Cost of Goods

I did not provide a CoGs for the LED system in my post “Introducing the  Components of the First LED Circuit.”   So I’ll provide one here:
 
 
 I could have used an Arduino for the timer but felt using a wall plug-in timer is a simpler and less expensive way to go.  Also, the Power Supply and timer can be used for additional LED set ups so the cost of adding more will be less than this initial cost (up to a point).
 

What’s Next?

I’ll be updating this post with weekly updates.  My next step is to focus on what I want to be notified and automated using an Arduino and RF – which right now I have moved on from nRF24 to JeeNodes in my exploration of RFs for home sensor networks.  More on that in the next post. 

 

submer