Ages ago, I funded a kickstarter for a “consumer molecular scanner”. It’s a pocket spectrometer of sorts that can be used with your smartphone to analyse the chemical composition of just about anything. It works by spraying an object with photons from an LED on the device. Different chemicals react differently with different wavelengths of photons. On the device is a sensor, that analysis which photons bounce back.
The android app that you use with the device, communicates over bluetooth to read data. Data is then sent to the cloud for analysis. What comes back is a spectrum that represents the object. Included in the app are a number of applets for doing things from estimating body fat to estimating the BRIX rating of a fruit product. You can also create your own “mini-applet” to capture and analyze your own objects.
Tomato leaf deficiency mini-applet
I wanted to create a mini-applet to analyse tomato leaves and perhaps identify any deficiencies. I started with some healthy leaves and took some scans. Unfortunately, I need to produce leaves with known deficiencies, scan those leaves and name those scans after the deficiency for this to be really useful. I did however, notice some strange leaf formation, took some scans and the results were different than the normal “healthy” leaf. If I can identify this as a nutrient deficiency, I’ll have a good way of identifying it moving forward.
Produce Selector applet
This is a built-in applet that allows you to scan your favorite fruit and get a BRIX rating. BRIX is basically the sugar content in a solution. Unfortunately for this applet, it didn’t recognize any tomato I scanned :(. I scanned my unripe fruit and the store bought roma tomato. I provided feedback via the app to the developers. I hope there will be an update soon.
Fruit and Vegetable applet
This applet lets you estimate the carb content in the fruit or vegetable. I used this on my unripe tomato growing in my greenhouse. It came up with 5% carbs.
I snapped a picture of the fruit and I’ll be able to check later for changes. I’m exciting to see what happens over time with these readings. Here’s the “spectral fingerprint” from my phone (5/10/17):
For comparison purposes, I scanned a store-bought roma tomato. The readings were identical from what I can tell and I’m not sure exactly what that means yet, but another scan of my greenhouse fruit when its ripe might reveal something.
The SCIO is pretty fun. I foresee it will be very useful moving forward to help identify plant and fruit quality.
If you are following my youtube channel, you’ve probably already seen this. If not, here it is again. This is an introduction to grow lights where I cover what are the important aspects of light relevant to plants and compare a couple different types of grow lights (T5 vs LED).
To sum things up, T5’s are cheaper out of the gate. But LEDs are more bang for the buck in the long run.
Far red (740nm) might be very beneficial to tomato production. Studies have shown that it can help produce longer “hypocotyl” (the seedling shoot that becomes the stem) by just blasting the plant with 12 minutes of light at the end of the day (16hr photoperiod with T5 lights). Other studies claim that far red can help reduce or eliminate sucker growth.
According to my research, blue light is primarily used in plants for vegetative growth. It follows, therefore that blue light is best for seedlings and clones that you want to grow in size quickly. Is this logic sound? I’ll experiment, and report back.
This video is a live build video where I make a $54 dollar blue-only grow LED floodlight. Note that at the time of posting, the floodlight price has already changed on Amazon. You can typically find these on ebay for a reasonable price.
The particle photon is a cool little wifi device. It’s relatively inexpensive, it connects to the internet, and I’ve been using it for several components in my smart greenhouse project. I needed to add a second irrigation system so I recorded how I built the controller and wrote the basic code to make it “web enabled”.
This video guide is incomplete, but it gives the basics on how to get up and running with your own web enabled internet device.
As a comparison, the Cyber Rain Residential Series 8 zone is $500. It does control 8 zones, and ours can only control 2. It also does not come with the electric valves like ours does. To make a better apples to apples, we’d have to remove the valve from our list and add a bigger relay with more channels. This relay supports 8 channels and is $9. We’ll also need an additional level shifter adding another $1.50. Here’s the new breakdown:
Granted, the software of the Cyber Rain is superior. It supports advanced timers and monitoring. We don’t have that, but we can add all that by writing more code. Let me know if you want me to do a walk through on how to add more smarts to the irrigation controller. I’ve already done it for my setup.
The first law of plant growth is light. Typically this light comes from the sun at an incredible intensity of up to 100,000 lux (lm per square meter). Different plants have different sunlight requirements. Typically these are categorized as “full sun” or “partial sun” plants. Full sun plants require at least 6 hours of direct sunlight per day (30,000 – 100,000lux). Partial sun plants need about 3 – 6 hours.
Winters in the Oregon Portland area are dark. So dark that humans suffer from the lack of light. This condition is known as Seasonal Affective Disorder. Most of this period is dominated by overcast clouds which reduces the light to about 1000 lux. That’s 3% of the minimum light required for full sun plants. To grow food all year round, we are going to have to compensate for this lack of light.
There are many different types of artifical lighting. The most power efficient of which are LEDs. The problem with LEDs is that they typically have a very narrow range of light. To make white, LED’s combine 3 diodes with some red, green and blue. The human eye sees these three as white. It cannot perceive the gaps in the spectrum that the LEDs do not transmit.
White LED from Cree (TM)
Other light sources cover a lot more of the light spectrum.
Given that lights light incandescent lights have a wider spectrum, why use anything else? The answer is, plants don’t need all that light. Plants use light in the blue and red spectrum and reflect the green and yellow spectra. That means that any grow light that includes these wavelengths are wasting energy.
LEDs for growing
LEDs for growing do not have the green diodes. This makes LEDs, which are already the most efficient artificial light source available even more efficient for growing. While you can purchase may LED-based artificial light solutions, I set out to build my own in such a way that I can control the amount of light my plants get based on sunlight. If there is full sun, I don’t need to activate the lights. If there is less than full sun, I can adjust the brightness of the LEDs to compensate.
I found some grow LEDs on ebay for a decent price from the seller sungrowled. These are 30W but I have also used the 50W variants.
To keep the LEDs cool, I picked up a 36 inch aluminum strip and mounted 6 LEDs evenly spaced on the surface. I used thermal adhesive to mount them.
On the ends of the strip, I drilled a 3/8″ hole and attached something I could attach to some rope to hang.
I then wired up the LEDs in parallel.
The aluminum strip helps spread the heat, but probably will still get to hot. To increase the surface area for cooling, I used the thermal adhesive to attach some aluminum heat sinks to the top of the strip opposite of the LEDs. This unit will be passively cooled.
Six 30 Watt LEDs run at a total of 180W. Amazon has a bunch of adjustable current/voltage power supplies from Drok. Oddly, the power supply ratings seem to go from a few watts to 100W and then jump to 300W and then to 600W. Really? No 200W? Sigh. I grabbed the 600W power supply version. To supply the AC power, I picked up a 300W 24V AC to DC converter.
What’s nice about the Drok power supply, is that I can supply constant voltage AND constant current. LEDs have an upward sloping current draw relative to the forward voltage. This means if you oversupply voltage, it’ll draw enough current to burn out.
Typical ways to drive LEDs include supplying a constant current, so that you can safely over drive the voltage, a resistor which will also limit the current, or constant voltage. If you never go over the volts, the current draw will be just fine. With this Drok boost converter, I have POTs that I can dial both. I started at 24V and slowly adjusted both the current and volt POTs until I read about 170 Watts on the kill-o-watt. Waddayaknow! It worked! It’s really… really bright too!
To finish off the light power, I put both the Drok buck boost converter, the AC-DC power supply, a couple fans, and Drok buck 12 power supply in a nice case and mounted it in the redhouse.
At the moment, our lights are dumb. They turn on and off manually and do not care about sun. We need a smart controller. I used the Particle Photon, which is a cheap wifi-enabled MCU that’s only $20. I’ve been using the photon a lot lately. This is actually the third unit inside the Redhouse and I plan on using at least one more. We also need a sensor to measure how much light we are getting from the sun. I had an SI1145 sensor breakout from adafruit laying around so I used that.
To control the LED brightness, I use a MOSFET. By modifying the signal’s pulse width on the MOSFET gate, I can control the voltage allowed to pass through the MOSFET. I wired everything up, wrote a few lines of code using the Particle builder and this is what came out:
The light sensor won’t work without light, so I need a case with a clear lid. I found a waterproof project case on amazon that had a clear lid. Perfect. I installed the board in the case, wired it up, and installed it in the Redhouse.
How much did this cost me? I try not to think about it, because I’m not building to necessarily save (although, I believe I am). Here’s a list of components and their costs:
6 x 30W LEDs – ebay seller sungrowled – $77
Aluminum strip and screws – home depot – $15
24V AC-DC 350W converter – Amazon.com – $35
Drok 600W buck boost converter – Amazon.com – $21
5 x aluminum heatsinks – Amazon.com – $25
Power enclosure – Amazon.com – $30
Grow light hanger – amazon.com – $10
Particle Photon Wifi MCU – particle.io – $20
SI1145 visible light sensor – adafruit.com – $10
MOSFET n-channel – sparkfun.com – $2
For comparison, you can get a nice (but dumb) 160W grow LED for about $350. No wifi/internet control. No smarts.
I think I saved some bucks and get more features. Here’s the final product growing some nice Roma variety tomatoes:
Do they work? Early indications suggest they do. The plants under the light look more lively. One plant NOT under the light has a livelier branch under the light where the other branches are not as lively. So, pending future observation, I conclude, it works. I only have 2 more of these to make :).
I may have built up my own excitement, but the redhouse (geo-thermal “smart” greenhouse) is really coming together. In theory, I can put my overgrown bathtub tomato plants tomorrow. This makes me extremely excited. On to the test.
This test will see if the pump, the piping in the beds and the irrigation system all work. These are the questions this test was hopefully going to answer:
Will the pump have enough pressure to water both beds?
Will the holes drilled in the irrigation PVC spray acceptable water?
Are there water leaks?
How much can I water with a 7 gallon reservoir?
Most of the answers can be found in this video:
The short version of the test is:
Enough pressure? Yes
Leaks? Yes. Around the valves and in the pump box
7 gallon enough? Maybe not.
The reservoir is the biggest disappointment. I quickly ran out of water in the 7 gallon barrel during this test. Further, it fills up slower from the rain water store than I can put into the soil beds. This will likely limit my watering to only a couple minutes at a time. I will also have to be careful not to run out of rainwater. If I need 14 gallons per day of water, I’ll only have 7 days in the store (two 55 gallon tanks). It is possible to use my brothers two barrels. That will give me a couple weeks and worse case I can fill up the tanks with house water.
Next test should be hooking up the controller. We should be able to start getting some measurements to see the benefits of the geothermal system.
Another important part of this automatic irrigated raised garden project is rainwater gathering. Instead of using expensive house-water, we can gather and use “free” rainwater from the sky. Untreated rainwater is more health for the plants.
I’m using two 55 gallon drums that I was able to find on craigslist for about $20 a drum. I got an extra two drums for my brother.
All four drums fit snugly in my minivan for transport back home.
After getting them home, I need a support structure to put them on. A friend of mine offered me a pre-built structure that his mother was using. I accepted and with a few modifications, this is the result:
This is situated right around the corner from the first raised garden. It will not take much tubing to get the water there. Also, the top of the drums is 7 feet. This will give me about 3 PSI of pressure (assuming 2.3 ft/PSI). That should be enough pressure.
Update: this post has been over a month in the making. During that time I’ve had no rain to fill the drums. I have water now and it works! Part IV we will look into hooking up the Edison and making a schedule.