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Dirt Cheap Modular LED Lighting System

A very affordable lighting system that can be used for ambient lighting as well as efficient grow lights for indoor plants.

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The system consists of small and very cheap modules (2€ total) that can be attached to three 5mm metal bars for mounting and power supply at the same time. This is achieved with 5mm fuse holders which makes the modules cheaper because no complex mechanical assembly is required. The bars can be attached to any surface with a modular 3D printable mounting kit consisting of just 2 pieces using a single screw.
The third bar is for sending either a voltage or PWM signal to the modules for dimming. The power injection board features a potentiometer for dimming and a ESP8266 for dimming over the network to integrate into any home automation system. A small switch makes it possible to override either dimming option. There are a few GPIOs and the ADC broken out in case the user wants to do plant monitoring or else.
I want the low price to be available (nearly) everywhere in the world and the assembly should be easy to do for everyone who can use a soldering iron.

The idea came from the need to have cheaper grow lights for IKEAs Hydroponics system. Their lamps are incredibly expensive even though its just a LED driver with a bunch of full spectrum LEDs mixed with white LEDs.


After two iterations that worked well for growing plants but were rather nasty to install and in-flexible, I wanted to iterate once more to make the system more adaptable to different situations other than IKEAs hydroponic beds. Installation of the LED modules was the trickiest part and I had a hard time using them in other places of my house to grow plants that are in need of light during the winter months.

A colleague of mine was also interested in grow lights (also for the IKEA system) so we got together to develop a new system. The idea we got was to use metal rods to act as a fixture and to act as the energy supply. The idea came from these old wire and track lighting systems:



Nothing new but the smart and cheap part was to use 5mm fuse holders to attach to the rods instead of a complicated mechanical assembly. This simplifies a lot of things.

Specifically this type of fuse holder is used.

Unfortunately I couldn't find any one of them without the stopping clip, so that will have to be removed with side cutters. A quick process fortunately.

My colleague went on to design a fixture for the rods that would be easily adaptable to different situations and I went on to develop the LED modules and the power injection board. Both PCBs utilize fuse holders to inject or receive power to/from the rods.

Given that the rods are so thick you can use cheap steel rods instead of copper rods without any significant voltage drop over several meters.

The LED modules itself are based around 3W LEDs in a widely used Luxeon like form factor. You can get these LEDs in all kinds of colors including "full spectrum" LEDs that only emit the spectrum needed by plants. You can get them for 0.14-0.25€ from AliExpress or eBay. The driver is based on the dirt cheap PT4115 constant current LED driver, which only needs 4 components to do its job. I'm also designing a second PCB that can accept a module version of that driver circuit which makes soldering a little easier and faster. These modules are also readily available from AliExpress and eBay for around 0.90€.

Everything is still in the prototyping phase but power delivery over the rods and fuse holders is tested on a prototype LED module and is working perfectly. You can slide the module around without any flickering.

Here you can see both module together mounted on a set of rails. The version using the driver module had to be a little bigger than the version with the integrated driver.

As you can see the PWM rod also acts as a mechanical reverse polarity protection. In addition to that there is also a big diode on each board to protect against reverse polarity.

upper plain.stl

3d printable holder clip. upper part, no hook or screw hole.

Standard Tesselated Geometry - 129.96 kB - 04/17/2017 at 12:02

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lower plain.stl

3d printable holder clip, lower part

Standard Tesselated Geometry - 461.41 kB - 04/17/2017 at 12:02

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upper side open.stl

same as upper plain.stl, but with a hook for mounting on the sides

Standard Tesselated Geometry - 312.58 kB - 04/17/2017 at 12:02

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upper side closed.stl

same as upper side open.stl, but with a screw hole instead of a hook

Standard Tesselated Geometry - 490.51 kB - 04/17/2017 at 12:02

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lower rear open.stl

same as lower plain, but with a hook for mounting on the rear

Standard Tesselated Geometry - 456.23 kB - 04/17/2017 at 12:02

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lower rear closed.stl

same as lower plain, but with a screw hole for mounting on the rear

Standard Tesselated Geometry - 521.96 kB - 04/17/2017 at 12:02

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plamp.3dm

Source file with all the geometries for the 3d printable holder clips. Rhinoceros 5 format.

3dm - 4.56 MB - 04/17/2017 at 12:03

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  • 1 × PT4115 LED Driver IC
  • 1 × 47uH Conductor
  • 1 × 100uF Capacitor
  • 2 × B340A Discrete Semiconductors / Diodes and Rectifiers
  • 5 × 5mm Fuse Holder
  • 1 × .13 Ohm Resistor For setting the constant LED current
  • 1 × PT4115 LED Dimmer Module For the module verison with inlay PT4115 based dimmer module.

  • Some 3D prints and first test with the IKEA system

    Professor Fartsparkle04/14/2017 at 18:50 0 comments

    I printed some of Max fixtures and altered them a little so they can fit the mounting holes on the IKEA system. In the end there will likely be a ton of different fixture combos that cover all kinds of situations.

    I think the picture speak for themself. The fixtures are really nice you can snap the lower part onto the rails and then slide in the top part from the side.
    The prints are not of the best quality but they work perfectly mechanical wise.
    I will add some photos later when I actually mounted the whole thing on the IKEA beds.

    This one uses a slightly modified top part, instead of the hole for the nut it has a 11mm hole that fits the little mounting hole thing on the ikea hydropnic beds ( compact: http://www.ikea.com/de/de/catalog/products/90319065/ bigger one: http://www.ikea.com/de/de/catalog/products/00319003/). If you zoom into the compact light fixture I linked you can see in the top right corner the mounting hole I'm talking about.

    This is the normal middle one. I didn't use countersunk screws as I didnt have any but normally you would use a countersunk one.


  • Mechanical parts

    Max Wolf04/03/2017 at 22:42 0 comments

    An update for the 3d printable holder clips: There are now different options to mount the rails either against a rear wall, against a ceiling or between two walls.

    check the picture. File names are self-explanatory.

    Now uses M4 countersunk screws for better compatibility. Needs M4x10mm ideally.

    To mount against a ceiling, just replace the M4 screw with a wood screw for example.

    These print fine on an Ultimaker 2.

  • Heat issues

    Professor Fartsparkle04/01/2017 at 23:07 3 comments

    Previously I ran the 3W LED Quartets at about half the maximum current, heat dissipation worked fine with some big exposed pads on the PCB. With the new modules I wanted to run them at their full specified current of 700mA but that turned out to be a thermal nightmare. I would have to add a huge heatsink to the LEDs in order to keep them at around 50°c.
    So I have two options, stick with 3W LEDs and limit the current to 400-500mA or go with 1W LED chips.
    Considering a low price point while still being a very usable thing is my main selling point for this project I will probably switch my design to 1W LEDs and do some testing if I can get a way with exposed pads on the back side of the PCB. If not I'm thinking about attaching some thin copper shims to the back, you can get them for around 17 cents for a 20x20x1mm one (at qty 50, see the link below).


    https://www.aliexpress.com/item/50PCS-20-20-1mm-20x20x1mm-Copper-Heatsink-thermal-Pad-for-Laptop-GPU-CPU-Radiating-Copper/32734955882.html

  • Power Injection Prototype

    Professor Fartsparkle03/27/2017 at 00:24 0 comments

    I soldered up a prototype for the power injection/dimming module. It looks a bit weird but seems to be working so far, the potentiometer glitches a little in certain positions. Which may come from the fact that I accidentally wired it up the wrong way. While the diode should prevent damage, something started smoking, will have to investigate why that happened.

    But power delivery was working fine for a single module at 16V 0.7A.

    Some photos:

    Normally the ESP wouldn't be on these stacking headers of course, I just used these so I could solder them on the component side as this is a single layer PCB.

    Mounted:

    Mounted

    Module powered up, dimmed down to ~30%:

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Discussions

Ember Leona wrote 03/31/2017 at 22:41 point

LIKED! do you think you can grow in gellatin or would it mold cololidial silver might prevent mold? I think the gellatin will liquify if heated so hydroflush. Maybe AGAR?

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Professor Fartsparkle wrote 03/31/2017 at 23:56 point

Not sure what your question is? This is only providing light and is not a complete system for growing plants. You can certainly use whatever substrate you want for your plant. Heat wont be an issue for anything under the lamps as long as you are about ~15cm away. There is not much heat radiated by the modules, though they do get very hot so nothing should touch the modules, a plant that grows too high into the modules so it touches them will likely dry up and crumble at the top. 

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DusanKo wrote 03/28/2017 at 18:09 point

Hello, first of all I would like to tell, that this is great idea. I am a bit worried about cooling of 3W LED's. I am afraid that the pcb size is not enough. Did You s older the led pads as well? Thank you.

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Professor Fartsparkle wrote 03/31/2017 at 22:35 point

Yes thermals is definitely something I'm worrying about. It would be great if all those LED modules would have there center pad unconnected to any of the leads but unfortunately there are some versions that have it connected to LED-. Otherwise I would have it connect to GND which connects to a thick metal bar, would have been a great heatsink.
I will put a lot of via's on the center pad to pipe most of the heat to the back copper layer which will have about a quarter of the board for each LED. That might be enough if not I will have to think about a heatsink for the 3W LED version. The 1W LED version of these modules shouldn't have any problems with heat.
I did not solder the center pads so far but I put some thermal paste on the pad.

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Yann Guidon / YGDES wrote 03/26/2017 at 19:42 point

Nice engineering !

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Professor Fartsparkle wrote 03/27/2017 at 11:47 point

Thank you :)

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ken conrad wrote 03/26/2017 at 14:57 point

What is the power requirement for each board and how many can you use per meter or per system?

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Professor Fartsparkle wrote 03/26/2017 at 18:57 point

Depends on the configuration. Right now I plan on using 3W LEDs which need 700mA but you only need to change a resistor to have a 300mA LED driver to use 1W LEDs. The module is also available in 3W and 1W configurations.

Taking that into account the actual consumption per 3W LED is around 2.6W. 2.6*4 is 10.4W. You need about 15v to drive a module. So the minimum requirement is 15v@700mA. How many of these modules you can use per system totally depends on your power supply and the current capability of the power injection board. Right now the power injection board will be your most limiting factor if you use standard 0.35um copper traces. I think in practise you don't want to use more than 8 per meter. If you want more module per meter I would go with 1W LEDs, you can that nearly triple the amount per meter. For ambient lighting the 1W LEDs will be much more sensible, the 3W LEDs make most sense if you use them as grow lights the amount of light they produce is way too much for most room lighting applications.
Physically you are constrained to a maximum of 20 modules per meter for the module based version and 22 for the version with the integrated driver.

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ken conrad wrote 03/27/2017 at 03:13 point

thanks! good idea, nice execution BTW!

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davedarko wrote 03/26/2017 at 00:26 point

that's clever and simple, I like it :)

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Professor Fartsparkle wrote 03/26/2017 at 00:31 point

thanks!

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Jan wrote 03/26/2017 at 09:19 point

+1

Only thing I have in mind is corrosion. Hydroponics/Plants always emit some amount of water vapor. Rods could be stainless, but the clips/PCB?!

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Professor Fartsparkle wrote 03/26/2017 at 13:50 point

Stainless steel rods is what I have in mind, they are also the cheapest with about 1.5€ per meter. The fuse clips are tinned copper, they are immune to corrosion by water. The PCBs will be manufactured and will have tinned pads as well, the copper boards are just prototypes. The 2€ per boards includes manufacturing of the PCBs.

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