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Thread: DIY remote controlled LED fixture

  1. #1

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    DIY remote controlled LED fixture

    Index
    Part 1 - DIY LED fixture (this post)
    Part 2 - Custom PCB and electronic components
    Part 3 - Software overview

    Part 1 - DIY LED fixture
    I'm in the process of assembling a DIY LED grow light fixture that is remotely and automatically controlled (MySGrowLED) and I thought that it may be worth sharing here. Most recent updates will be available on github.
    This use an open source project, MySensors, that allow to wirelessly link sensors (temperature, humidity, soil moisture, pH, light levels, ...) or actuator (light, relay, switch, movement) using arduino and raspberry pi hardware.

    Right now the setup is working but the electronic part is still on its prototype form. I designed and ordered a custom PCB which should be there soon, worst case scenario in a couple of weeks.
    Once this part is finished I will also share it here. In the meantime, here is the basic setup for the LEDs, that can be controlled by a simple timer or switch.

    Components
    Total cost in parts is ~$95 for a real 60W LED light with a spectrum optimized for plant growth and photosynthesis (no green).
    Most of the commercial solutions are extremely deceptive on their real output an power usage. In this example, as we are using 3*50W chips, this would typically be advertised as a 150W light.
    This is totally wrong as only 60W of power will be used. It is not advised to run a LED chip at its nominal power as it will generate a lot of heat and will fail quickly!

    To create this 60W LED fixture you will need the following materials:
    - 3*50W full spectrum 45mil COB LED ($30, ~$10) each).
    Can be bought on ebay, aliexpress, etc.


    - 3*heatsinks able to cool down your LED modules ($30, ).
    In this case we will be using a DC-HS11132 heatsink for passive cooling.
    Heatsink come with 4 to 16 M3 screws and a pack of thermal paste for improved heat dissipation.
    Using a smaller heatsink, or running more power in the LEDs would require a fan. Using this setup, the whole assembly is at ~40C while running which is safe for the plants even at a close distance.
    This specific heatsink can be mounted on a 35mm DIN rail which will allow to link the 3 LEDs on a single bar fixture.


    - 1*mounting track, 35mm DIN rail Type, 1m length, (~$7).
    I used a 16-700DIN from Schneider Electric.
    Heatsink will slide on the rail and then can be bolted to it using the existing holes in the rail.

    - 1*60W LED driver to power the LEDs (~$16).
    I use a LPC-60-1750 from Mean Well that will provide 34V at 1750mA. LEDs will be wired in parallel (34V, ~580mA each).
    As this unit will be in charge of converting your main power (110-230V) to ~34V for more than 12h a day, every day, in potentially humid conditions it is very important to choose a power supply you can trust. You don't really want it to catch fire.
    I would not recommend buying the power supply from ebay or directly from china as you may end up with a counterfeit unit unless you are sure of the seller.

    - 1*PCB DIN rail mounting bracket (~$2)
    Will be used to mount the PCB to the rail. This is optional, if you prefer using a timer, a switch or have another way to control your light you can use this LED fixture as a standalone without the MySGrowLED part.

    - Misc (~$10)
    You will also need some basic supplies that you may already have, or will find at your local hardware store. You will also need to solder the wires to the LED chip.
    In this case you will need ~3m of solid 2-conductor cable and ~40cm of solid 3-conductor cable (optional if you are not using MySGrowLED).
    I used thermostat cable that can easily bought in roll or cut at your size at your local store.
    You will also need some wire terminal blocks to connect the wires, hex bolts and nuts to secure the heatsinks to the rail, some rope, hooks or any other way to suspend the LED fixture to your grow area.

    Assembly
    The whole process should not take too much time, probably around 1 hour without rushing it.

    LED assembly
    Start by removing the heatsinks from their package. They should come with at least 4 screws and a small pack of thermal paste.


    Grab a LED chip and lay it face down on a soft nonabrasive surface.


    Locate the thermal paste and carefully tear it open.


    Empty the whole packet content over the LED metal back...


    ... and spread it evenly over all the back surface.


    Grab the LED chip and using the provided screws mount it on the heatsink. Do not screw tight each screw one by one but do it in multiple steps to spread the paste evenly.


    Repeat for the 2 other LED chips and heatsinks.


    Soldering
    Cut your 2-conductor cable in ~1m segments. Decide which color will be the positive wire (red in my case) and negative (white).
    Locate the positive and negative contacts on the LED. They are the tiny metal wings on each side of the LED. Usually the positive side is perforated with 2 holes while the negative side only have 1 hole. You may want to check this using a multimeter. If at the end your lights don't light up it's probably reversed on your LEDs. Don't worry, just switch the wires on the terminal connector (see below).

    Remove the plastic insulator over ~1cm and solder the wire directly to the LED chip connector. Use as much solder as possible to create a good electric contact.


    Repeat the process for each LED unit.

    Final assembly
    Now that all units are ready you need to create the fixture using the rail.
    Bend the cable around the heatsink to have it sandwiched between the heatsink and the rail. All wires should be oriented the same way, toward your power supply output.

    Slide all heatsinks to their definitive position and secure them to the rail.


    On the end where all your wires are converging, thread the 2-connector cables into the second DIN rail hole. Thread the 3-conductor in the first hole (if using MySGrowLED) toward the second heatsink.
    Use a terminal connector to link all 2-connector wires together according to their polarity. On the other side link the 3-conductor using the same colors, leaving the extra color alone.
    Secure the terminal to the rail using a zip-tie.
    If you are using MySGrowLED link the positive output of the power supply to the positive side of your LEDs (red wire in my case) and the negative output of the power supply to the extra color of the 3-conductor wire (green in my case). If you are using a different control circuit link the negative output of the power supply output directly to the negative side of your LEDs (would be white wires in this case). If your lights are not working, probably because of a polarity error, switch the wires at the terminal, no need to desolder the wires!


    Add some rope, chain, hooks or other to suspend the LED fixture to your grow space.


    Mount everything (in my case suspended to a $25 IKEA OMAR shelving unit)


    Plug the power supply to the electrical main and congratulations, you now have a LED grow light!
    Last edited by emc2; 05-15-2016 at 03:10 PM.

  2. #2
    nimbulan's Avatar
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    Excellent work there. You should also note that running LEDs at their maximum power significantly reduces their power efficiency. Hopefully those COBs hold up too, I've heard the cheap ones generally aren't very good quality.

    I definitely know what you mean about the power rating of LED fixtures. I've seen people ask questions after buying a "300W" LED light and after doing a little reading I discover that it only draws 135W from the wall so the LED power is even lower.

  3. #3

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    True, power efficiency decrease significantly too. There is a very interesting video from bigclive on this subject 20W vs 50W LED lux test in a 20W floodlight. - YouTube. He actually use the same setup than I do, underdriving a 50W LED at 20W.
    If you are lucky enough to have a datasheet with the LEDs you usually see a sudden drop in efficiency when the chip is close to 70-75C. Most of them will fail past 85C.

    I hope these COB will last, I actually did not find any reputable seller of full spectrum LED so I assume that for now these are actually good quality. You can find equivalent 50W white LED for $2 so hopefully this is will be ok.
    I should add that cannabis home grower forums have ton of very good DIY LEDs setup (I ended up on this quite often while looking for informations). Most of these actually use more powerful white LEDs, which are totally fine for our carnivorous too, but as green is not necessary I wanted to try these.

    Rating of LED fixtures is really annoying. It's also true with the E27 screw bulbs you find everywhere. On my first try I ordered a 15*3W LED bulb advertised as 45W on amazon. It was only $18 (already suspicious) but was actually drawing only 12W. For growing basil in your kitchen sure it may work but definitively useless for full sun plants. This one was sent back but looking at the inside revealed a 20W max power supply so anyway it would never have reached 45W.
    Look in the comments section, people will complain about it, or else say nice things because they got it for free in exchange for a "honest review"...

    Finally as you mentioned, LED output is not the power usage too yes, when looking into the heatsink design I found that for white LED, 50% of the power was to be assumed as dissipated as heat (source: DIY LED Basics - choosing your heatsink (part 4/7) - YouTube ). It's surprisingly hard to measure the light output of a LED for plants (candela, lux, lumens, PAR?) even worse when not using a white light. This 60W fixture output between 7000 to 2000 lux depending on the distance and angle between the plants and the light source. But it means nothing as lux is designed for human eye which is the most sensitive in the green wavelength, mostly missing here...
    This setup is running since one month, most of the plants turned red in a couple of weeks and seems to adapt to the LED (dew start to come back on some of the Droseras). This is the best feedback that I can give so far.


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    Part 2 - Custom PCB and electronic components
    I received my PCB and so far everything seems to be working nicely so time for step 2: the control board.
    With the electronic components in, it introduces a nice way to control light, humidity, temperature or any other parameters either using an external controller or autonomously.
    You can use an array of sensors to provide feedback to the controller and then adapt the light levels and fan speed.




    Description



    MySensors module designed for wireless greenhouse automation (nRF24L01, 2.4GHz).

    This module allow you to:
    - control a primary LED light (5-40V input can be used to power the module)
    - control a secondary circuit designed for a CPU PWM fan but can be used for a second light, humidifier, relay or anything else using 12V
    - monitor temperature using an optional onboard DS18b20 sensor
    - monitor external temperature by plugging external OneWire sensors
    - monitor any additional parameters using additional I2C modules such as temperature, humidity, light levels, barometric pressure, etc...


    Ordering

    Gerber files are included, so you can order these PCB at your favorite PCB fab house.
    For an easy ordering process you can directly order these PCB from DirtyPCB or OSH Park without having to do anything.
    Components are highly customizable and the default list may not be the best for your specific use, but it will work for most of the cases. Double check that the power supplies, voltage regulators and mosfets are compatible with your project.


    Options

    This board is designed to be compatible with MySensors but can be used on its own (timer or sensors to control the lights) or another system using 2.4GHz communication if you adapt the arduino code.

    ATSHA204 module
    For security reason you can add a CryptAuthEE SHA256 chip. This will allow you to sign messages and will secure communications between the node and your gateway (this is not encryption, just signing).
    If you only control lights, fan, or other non-essential hardware you probably don't need to bother with this chip.
    Signing can also be done at the software level, without the chip if you decide to add this function later.

    Eeprom module
    This module is only used to perform OTA updates on the node. If you don't plan to use this feature you can also skip this chip.
    You will also need to burn a compatible bootloader to your arduino (DualOptiBoot)


    Assembly

    Once you received your dirty package of PCBs (or any other Fab house) start by inspecting it carefully to look for scratches, dents, or anything that seems wrong. Do not use the board if you have any concerns.


    Markings are a little off, but nothing wrong on this one, good to go!


    Start by soldering the optional chips, if you plan to use them.



    Then add all other surface mount components. Don't be affraid by their little size, they are actually easy to solder. If you never soldered SMD components before, be sure to look for a few video tutorials first.


    Finish by adding the regular through-hole components, starting by the smaller ones.


    Plug your arduino module and radio and you are good to go.



    Testing

    You can upload MySGrowPCB_test to your arduino to test the setup:
    - It will look for an ATSHA204 and return its serial number if detected.
    - It will look for an eeprom and return its manufacturer ID if detected.
    - It will alternatively switch the LED and Fan circuits ON and OFF for 10 seconds.


    Usage examples

    This module can be used on the DIY LED light exemple included (PCB compared to breadboard design)



    Another possible use to control a germination chamber inside a plastic container (PCB compared to previous protoboard design)




    Revision history

    Version 1.0: Initial release.
    Last edited by emc2; 05-15-2016 at 03:11 PM.

  5. #5
    nimbulan's Avatar
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    Looking good! When I put together a couple COB lights recently I ended up ordering directly from the factory in China since the part availability is very poor here. I use this one with high bin, 4000K, 70CRI (lower CRI is higher PAR generally): Cree XLamp CXB3070 LED Array It's definitely more expensive this way, but the Cree CXB series has the absolute best power efficiency on the market as far as I'm aware.

    I'll have to look into these control and monitoring modules in the future, and hopefully set up an automatic watering system with them as well.

  6. #6

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    Thanks.

    Yes these Cree are among the best ones. But for the price of one Cree I had 5 purple ones so good enough for me

    Anyway if you run yours at 36V it should work with your Cree.
    For a watering system if you use a 12V pump (I would say max 0.2A to be safe) it will work using the "Fan" channel.
    Else you either have to use a relay on the Fan channel or use a module by itself, but it should work too.

    Or you can even use a dedicated irrigation node to be extra fancy.

  7. #7
    Never Knows Best gill_za's Avatar
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    Hey emc2,

    Just curious if you are running your LEDs in series you are running each one at 1/3 max Vf (~11V) and all 3 will draw respectively lower current at that voltage (I know the LEDs are current driven technically). Is this why the lights are so dim? My concern is for ex. with laser dioded before the optimal current/voltage some will emit in the wrong wavelength/mode or for example will not emit coherent light. Are LEDs affected in a similar way?
    Last edited by gill_za; 05-11-2016 at 07:46 AM.

  8. #8

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    Actually these are in parallel (you can see it on the terminal block wiring, all red and white wire are together).
    So they are all running at the same V=34V. The driver is a fixed current (1750mA) one so each LED is running at 1750/3=~580mA

    If the lights are so dim on the last picture it's because of 3 factors:
    - thanks to the electronic control by the arduino I have a dimmer function. For the picture I use a 5% level (~3W) which make the lights quite dim. I will detail the software part this week end to give an overview of the possibilities in the 3rd and final post.
    - white balance being off, the camera don't like to take pictures of these things as it tries to adjust the balance while taking the picture (removing as much purple it can). I could turn that function off, but well usually I don't take pictures in a night club.
    - very short exposure time on top of that.

    I even had to add "space blankets" all around my shelfs, else the whole room was bright purple. It also "keep the light inside" by reflection which is actually better as I did not install any optics on the LEDs.

    Here is an old picture (you can still see the breadboard) that was at 100% but still with a short exposure as else you can't see much except a purple light.

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