After years of procrastination, the itch to get into hydroponics needed attention. Before jumping headfirst into the unknown, a quick experiment to see how the plants responded to neopixel LED strips was in order. As such, I’ve put the MEAN stack exploration on hold.

Objective

Can the neopixel LED strips provide enough lighting to grow herbs and other leafy vegetables?

Materials Used

• 2 x NooElec 1m 60-Pixel Addressable 24-Bit RGB LED Strip, 5V
• 2x BTF-LIGHTING WS2812B 144 leds/pixels/m
• 1x  DROK® DC-DC High Power Buck Voltage Regulator Board 5-40V to 1.2-36V
• 1x DS3231 AT24C32 IIC RTC
• 1x xbee S2C
• 1x Arduinio Mega
• 1x xbee explorer
• 1x LM35
• 2x 220 ohm resistors
• 1x 0.01 micro Farad capacitor
• 1x 1000 micro Farad capacity
• 1x soil moisture sensor (not required but I had it lying around for a while)
• 1x 12V power supply

Putting it Together

The following diagram illustrates the wiring.  The LM35 when used with other analog inputs leads to erratic readings. The capacitor stabilizes things.

The software is straight forward with the xbee operating using AT mode rather than API mode.  For now, I used modbus to communicate to Mango and for giggles VT-Scada. More on that in a future post as the IIoT speak I hear from certain vendors — not the two mentioned–make me cringe knowing what they have under the hood.

Software Feature List

• set time from host via modbus  or terminal console
• set lights on time via modbus or terminal console (default 18 hrs on)
• set lights off time via modbus or terminal console (default 6 hrs off)
• set duty cycle via modbus or terminal console
• set duty cycle period via via modbus or terminal console
• get temperature via via modbus or terminal console
• get soil moisture via via modbus or terminal console
• force the lights on or off via modbus or terminal console
• save/load/restores settings to/from EEPROM

Modbus was used as I already had a SCADA host running. It could have been xbee API or bluetooth. Having done both, this is relatively easy to refactor the code later.

The code can be found at https://github.com/chrapchp/PlantLEDLighting. Not the prettiest code yet it it does the job for this experiment.

Periodically changing the red/blue ratio aka duty cycle between 70-95% red with the remaining in blue light tainted the experiment. Regardless, it is logged in the SCADA/HMI host for further analysis.  Interestingly, the research around  LED-based plant lighting is growing along with plenty of do-it-yourselfers experimenting.

Lessons Learned

On the Mega front, the Chinese knock-off ended up with causing more trouble that they’re worth. Problems included the following:

•  voltage regulator fried
• TX1 via the header pin did not work
• headers were loose
• finding a driver took extra goggling

Needless to say,  I ended up purchasing the real one.

Wiring xbees on breadboards gets old fast. The current setup consists of switches to commission/reset and  a potentiometer to vary the input voltage for testing a device. Nevertheless, I  purchased the wireless connectivity kit  (S2C) and the pro version of the xbee  to facilitate the configuration and program some custom functionality in the xbee in the future. Highly recommended if xbee development is on the radar. BTW, digikey Canadian or US site offer great service and fast delivery. I’ve ordered from them several times.

Observations

Herbs

The basil and oregano took a couple of weeks to germinate followed with a slow growth rate.  In contrast to what others are doing, the growth rate falls far short with expectation.

Leafy Vegetables

The kale and arugula germinated in 3 days and grew relatively fast. The weak stems could be attributed to the LED’s . I’ve planted some outside as well and will compare the stem sizes with the indoor ones.

Minor Changes

The addition of a fan to create a light  breeze led to stronger stems. After a couple of weeks of circulation, the arugula and kale stems seemed stronger. The basil grew and looked healthy yet remained small. When compared to their outdoor counterparts, the healthier looking indoor basil prevailed.

Next Steps

There seems to be some confusion out there between lumens and pars. I read about people only measuring lumens for plants and scratch my head.  Consequently,  I like ChilLED‘s pitch in positioning their lighting products as well an intro-101 from Lush Lighting.

Incidentally, a buzz exists stating the effects of UV could lead  to ‘certain’ plants to produce more THC. Note, I am not interested growing those plants and just want to grow edibles all year round.  At any rate,  I think the root cause revolves around the low LED pars and power rather than the effects of different soil, nutrients, and seeds.

In short, I’m considering using ChilLED for sourcing my lighting needs provided that  controlling the output of the various channels without using their controller remains feasible.  Note  growmay5 provides some interesting vlogs on this as well as other topics around LED plant lighting.

Altogether, I’m satisfied with experiment and how quickly I could mash up a solution. Hydroponics is the next step with better LED lighting and queued for later this year as a project.

Kale

Temporary setup

Slapped together hardware