Smart Lighting for Home Cannabis Growers

A quick explainer; the elevator pitch.



Greetings, Jeff here. The LBD is taking its toll and the clear moments each day are coming fewer and fewer....which means writing anything at all really takes enormous effort, time and dedication, all things I have in short supply. Personally I thought I was done with this site; nothing wrong with it, it is simply taking more work and mental energy than I have to spend. And yet, something came along that I felt worth the time and effort to share with other cannabis growers and so I will do my best effort to outline it here. Final confession. Even doing this right is beyond me it seems so I will post here the various notes, videos, diagrams and pictures I had taken to support a much more detailed article. Just know two things: 1 I am sorry, truly sorry and 2. I did my very best.  With that warning, here we go.



I am presenting a simple modification to existing lighting systems that you may already have in your arsenal that can either reduce your energy use, heat generated and overall money spent, or it can be leveraged to safely use 33% MORE light in your environment without additional cost or power-line loads. 

Update/Edit (31 October 2022, after nearly three weeks of use): Hey kids, Jeff here, this is a short update to share the first good news, the system works and we have our first metric. Traditionally when I am maxing out at 300w of light per plant, the average temperature in those tents is between 88 and 93 degrees F. Not a really good zone for growing quality cannabis but living in the desert you learn to live with certain constraints, and sometimes excessive cooling is needed when its 120F just the other side of the wall of the grow room. In any event, in time I could always recognize when the plants were starting to bake...I did what I could but after years of trying, I realized my own limits. Then I came up with this and for the past 2-3 weeks the system has been in place in both tents, the plants are all looking just fine thank you (healthy and thriving) and best of all, when I go to check on them after they have been on for 9 hours of their "daytime" period in zipped up tents, and the air inside feels pleasant and refreshing, I know things are better for them, better than its been in years. A glance at a thermometer zip-tied to a trellis rig about 4 foot off the floor reveals the reason:

My tent temps during bloom haven't been this low in years.

End Update.

Jeffs SmartLight System V 1.0

Why Do This? Well FWIW in my rare moments of clarity I am writing down
the reasoning behind this along with practical steps and most
importantly to me, future directions this can and should be taken.

Summary: As a legal cannabis grower in the home, you come to have to
live within certain constraints:

1. You only have so many plants allotted for growth at any given time,
usually barely enough to provide using standard grow methods.

2. With the advent of inexpensive lighting for the home grower, it is
now easy to go overboard with lights to get more out of your crops.
The addition of easily mounted and very bright LED lights means you
can light more areas of the plant that is typically under served by
normal lighting methods.

3. This has resulted in many including myself constantly riding on
the edge of electrical circuit limits. This means risk of fire
(check), higher than usual electrical bills (check) and worst of all
for my area (desert), so much excessive heat that it can adversely
impact the growth of your plants (check, check and check).

So for anyone swinging for the fence when growing indoors its a
constant battle between all these forces when trying to get more out
of your crop. I could not live with the status quo and came up with a
solution that so far seems to be working fantastically.

First, the setup: in my grow we do something like vertical farming of
cannabis plants. Basically they are grown normally until they are
tweens (few weeks prior to bloom flip), at which point a vertical
trellis I made is mounted on the wall just behind the plant. The plant
is then flattened and pinned to the trellis. Since the plant is flat
at this point, light and air aimed horizontally at the flattened
plant. Every bud and leaf get the exact same saturation of light. This
is because instead of lighting from the top, I daisy-chain 1-3 100w
LED grow light panels from the ceiling in front of the now flattened
plant. No dead areas, no air buds and maybe best of all, you turn the
normally smaller buds into colas every bit as good at the top of a

So the solution I came up with was a twist on an older communications
method, the Time Division Multiplexer or TDM. In short, one of the
earlier challenges of mass (for the time) communications was how to
use a single wire and transmit 12 or more voice communications.

I realized as a...."performance" home grower or to put it another way
someone who swings for the fence...that my exploration of growing was
at a bottle-neck, disease not withstanding. The basic problem was:
* One thing that bugged me over the years was lighting was always
fixed and since the plants were too, you got only part of the plants
lit. They never got lit in their totality.  Working with the trellis
taught me that there was little that special about the top of the
plant, and that if properly lit any region on the plant can produce
top shelf bud or what most people call "tops".

* This turned into a good news/bad news situation. I knew to really
light all parts well I needed more lights and thanks to LED dropping
in price, this kind of intense coverage was at least possible. Bad
news is, using so many lights, low-consumption that they were, still
added up and with only growing enough plants for ONE license, I
overloaded our power and you know how that turned out.  One cool
benefit of this total lighting trick is we actually yield so much
usable bud per plant, we no longer even need to grow a single license
worth. we get 8 or 12 plants each and this is providing for both of us
with 5-6 plants.

* Another gotcha this brought was heat. By itself each light produced
little but get enough going and the tents stay around 90F any
"daylight" hours. This generally sucked but since most bud was for RSO
I lived with it.

So that was the situation. The conundrum.  How to use more modern
lights yet make less heat and use less electricity than current
methods.  They say dementia lets you recall really old useless shit
with ease and I am happy to say, they were right. I flashed back to
my US Army Signal Corp training back in the 70's. A communication
principle called Time Division Multiplexing or TDM. TDM solves the
problem of how to send multiple voice conversations down a single wire
without everyone talking over one another and hearing what everyone is

Note: OK I was going to insert a simple explainer on TDM from the net
somewhere but imagine that, Google found no hits for "time division
multiplexing for dummies". Thus the gentle reader is stuck with my

Recall the original problem was: how to have more than one voice
conversation on a single line. I found it weird that most explanations
of this are from IEEE or other trade organizations and yet the
principle is so simple.  OK simple story time:

Say for example I lived in my house and you lived in your house.
Further, we each had four people in separate rooms with telephones all
wanting to talk to their counterpart at 1:00pm. By that I mean, at
1:00pm the person in room 1 at my house is expecting to speak with
(and only with) the person at your house in room 1. #2 is expecting to
speak with and only with your #2 and so on, all at the same time, and
there is only one phone wire between us.

Now finally assume that all four of my rooms are wired to the room in
the basement where I live. In this room I have these four lines wired
to a rotary switch that connects to the outgoing phone line. You at
your house are set up in a similar fashion. In this arrangement on a
normal day if my #1 calls me and asks to be connected to his
counterpart at your house, I would turn my switch to position 1 so his
room is connected to the outside line. Further at this point, you
would do the same: turn your switch to position 1. At this point, #1
has a pretty direct connection to the other #1.  If my #3 wanted to
chat, you and I would set the switches to position 3 and they could
yack all day long. However it gets sticky if say the number 1s and
number 3s all wanted to speak to their counterpart at the same instant.

TDM to the rescue. To solve this, we use time division, meaning
instead of #1 being connected all the time, you (as the switcher in
the basement) switched back and forth between #1 and #3, and further
assuming I did the same, in perfect sync with you, then #1 gets the
wire half the time, then then #3, then back to #1 and so on. Now
finally, assume that not only are we (you and I being switchers) in
perfect sync, but we can also do it 10 times a second. This would
result in the people talking on #1 and #3 perceiving no switching or
breaks in the communication at all since its faster than a human brain
can percieve. Even with all this switching going on, all you hear in
clear conversation.  Obviously at this point in the story, its not
really you or I doing this switching, its a machine because only a
machine can operate fast enough for this to work and not make mistakes.

More info on TDM: Wikipedia article on TDM

This is the basis of time division multiplexing. Originally this was
dreamt up in the 1800s for early phone companies because they sure as
hell didn't have multiple lines between stations. When I was in the
Army in 79, our typical MUX as it was called handled 24 channels of
input shot out via a single microwave beam, then was sorted back at
the other end. There was crypto involved too but thats another story.
For a final comparison, the top speed of our switchers in 79 were
about the speed of a DSL line or cable modem.

If I find a better explainer I will stick it here but in an effort to
move on for now, the take-away here is this: a single resource (in this
case power and light) can be shared amongst more than one recipient
using this trick, only instead of quickly switching voice channels, I
periodically switch grow panels on and off. This way I can light much
more plant using less watts and heat than before.  So right now every
stack of three panels lighting top, middle and bottoms of my trellis
plants is split into three zones. The middle zone is lit all the time
(for the light period, so right now, 12 hours). Then through the use
of timers I have the tops of the stacks turned on for two hours, then
the tops go out and the bottom panels come on. Lather rinse repeat
throughout the "daylight" hours. Two hour cycles is a purely arbitrary
value, my hope is to achieve the same thing with light as early TDMs
did with telephones. Thru programming of timers the lights are
constantly rotating and everything is getting intense LED output for
half of their day and about 80% normal when they are in an "off" cycle
so its not like light is going away completely. I am drawing up charts
and shit to help describe this for the final document.

This setup is now our default and already we have noticed two really
important signs:
1. The temps in the tents have dropped drastically after being on all
night. Goal achieved maybe.
2. The plants seem to not be suffering in any way and certainly in no
way that screams light deprivation.

By virtue of #1 I feel safe in saying that power consumption has been
reduced by some measurable and non-trivial value.
By virtue of #2, I feel safe in same that while there is a very high
chance in the yield per plant not being negatively impacted by this, I
also must confess there is a chance yield may even increase slightly
due to this for two reasons: first, the way lower temps will make the
environment much less hostile to optimal plant growth and second if
this is brought to its logical conclusion, you will be able to put
lots of smaller lights literally everywhere around a plant, aimed at
everything important and have a simple Raspberry Pi or other board
like that do intelligent power switching. In fact I already have
another dude working on this, though he doesn't know it yet. But if
smart management of the timing is combined with total and complete
plant coverage, its not unrealistic to think this will pull another
5-10% in.


* 2 hours is arbitrary but a line of research might be this: What is
the plants light-equivalent of the voice TDMs fraction of a second
when a channel or person isn't really connected...this is fast enough
to provide the illusion of a continual, uninterrupted conversation.
The light trick seems to work a lot slower and it does but this is not
without thought. In the same way there are dog years, plants grow and
mature at a totally different time-scale than humans and human life.
As such, the size of the period where a plant won't "notice" the
missing light needs to be established. For now, two hours works fine.

* This is a germ of an idea for....something. I don't know what but it
needs to be taken further by someone smarter (and still around) than I
am. I think it should be reduced to a Raspberry Pi setup so its more
of a device than computer for an average user plus something like a
Raspberry Pi board would allow for more complex lighting schemes to get
even more out of your crop.

*My methods will suffice for smaller ops but it would be interesting
to see someone take this beyond basic lighting, such as large banks of
panels programmed in such a way that natural sun motion is imitated...