THE GEM - 500W [Light&heatsource]

HEAT CIRCULATION vs LIGHT
Case: Imagine a part of your living space, where you can grow greens all year round, and at the same time use the heat-output to warm up your space. This could not only provide food all year, but also expand the outdoor season by starting sprouts indoor, in a controlled environment, before they are ready to be planted out.

Another mayor benefit by utilizing the radiated heat, is the possibility to fully heat your living space with green energy. This means less foresting for wood to burn. Less Co2 emissions from NOT BURNING WOOD or other carbon-based energy sources. Naturally all this requires a solid environmentally friendly energy infrastructure.

By introducing CAN (Controller Area Network) to the "intelligent" GEM/lamps, if several lamps are connected only a "Master" CAN node will need a connection through either USB or wireless. This means a great deal in a greenhouse scenario, where many lamp all need to be monitored and controlled from a central hub. Likewise only one wireless module in the network is necessary, depending on the case.

UPDATE: The process of finding the best pcb for high current LED´s led me to Metal Core PCB with sinkpad´s. Sinkpad connects the cooling surface of the MCPCB and heat pad on the LED. This gives a x100 performance in heat transfer and thereby optimizing cooling. Literally the LED´s will be mounted more or less directly on the heatsink. The PCB´s has been ordered and I am making the final adjustments to the heatsink.

CREE LED´s

https://www.cree.com/led-components/media/documents/CreeXLampHorticultureFeatureSheet.pdf

Design

The design is starting to manifest.

White LED´s use energy to lite up the full visible spectrum. The Red and Blue only one wavelength(area) and is therefore cooler in use. The difference between the red and blue wavelength is another matter.

For office environment the fully white GEM would be more pleasant for the human eye. In a school scenario the lamps would be part of photon to plant growth process.

The Controller for the lamp has 40 amp rated MOSFET´s (Switches). How fast the controller is able to switch the switches depends on several factors. One main factor is the switching resistance Rds(on) and naturally the frequency of switching. Since the controller inside the lamp is actively cooled by the 60mm fan right next to it, a small heatsink directly on the MOSFETS would make a significant difference.

As seen in above image, the positive power line is fortified with a 1.5mm x 1.5mm busbar (square copper wire). This should handle up to 45 amp. with a temperature rise below 10C. The wire-lugs for the wire going to the PSU is rated at 65 amp.

Project Logs

Collapse logs

Temperature Probe
Juan-Antonio Søren E.P. • 3 days ago • 0 comments

To obtain the best possible control of the LED´s, we need to measure the temperature as close as possible to the LED heat pad. This will be done using a classic E3D thermistor in a cartridge (https://e3d-online.com/products/thermistor-cartridge). The sensor is 15mm long with a 50mm cable w. a good secure connector.
Dimensions
Juan-Antonio Søren E.P. • 01/09/2021 at 14:24 • 0 comments

In order to scale the wire connection to the MOSFET 40amp rating, Ive chose to fit 65 amp power lugs.
Heat exchange
Juan-Antonio Søren E.P. • 01/07/2021 at 18:21 • 0 comments

Heating or cooling the heatsink is entirely dependent on current consumption and ambient temperature.

Looking at the heatsink, it is obvious, when pushing cool air across those fins, the air is gonna heat up. The above heatsink is for the small version 254mm long, 80mm wide, 40mm high.
Wire Shielding
Juan-Antonio Søren E.P. • 01/04/2021 at 13:19 • 0 comments

The LED phases must be soldered to the LED side, since the MCPCB is single sided. To shield of the solder points and wires, some sort of shield is is necessary.
Channeling
Juan-Antonio Søren E.P. • 01/03/2021 at 14:29 • 0 comments

To raise the light up into the enclosure, some sort of air channel is needed. This channel will also serve as mounting bracket for the wooden enclosure. On the LED side, the channel/bracket will provide mounting holes for wire shielding.
GROW AREA
Juan-Antonio Søren E.P. • 01/03/2021 at 10:25 • 0 comments

The Cree XP-G3 LED´s have a illumination angle of 125-130. Subtracting the outer 10% the grow area at 50cm height is 2m x 1m = 3m2. At 1 meter the average µmol/sek. naturally becomes lower, but will illuminate approx. 3m x 3m = 9m2. One of the advantages of LED´s for grow lights is the moderate heat radiation, which makes it possible to get close to the plants without heating up the top leaves, to much. Plants like moderate heat when utilizing the photons to produce plant matter. To achieve the best possible growth, the temperature around the leaves should be regulated. Furthermore it is a good thing to have air flowing across the leaves to evaporate moisture and thereby pull the chain of molecules going all the way down to the roots, where nutrition's are dwelling. The optimal man made system for plant growth will therefore take all these variables into account. The exces heat from the lamps, can be used to provide a optimal temperature inside the growth environment. The heat not used to regulate the growth environment can in turn be used to heat up a living space, it could be stored in eg. water or simply discarded. The trick here is to find the right balance.
Xploring Enclosure V2
Juan-Antonio Søren E.P. • 12/27/2020 at 10:41 • 0 comments
MCPCB - METAL CORE PCB
Juan-Antonio Søren E.P. • 12/24/2020 at 07:09 • 0 comments

Since there is no looking back now, there is only moving forward, MCPCB seems like the only logical choice. Will try to find a way to design the files in Kicad.

From what i gather here and there, no vias (or very few) is allowed.

It´s possible to make it with 2 copper layers. Either with aluminium sandwiched in the middle or as a backing plate.

Im thinking to maintain the fan´s.

Now, having come to the conclusion, that the heat-dispersion (cooling) and thereby the mechanical buildup of the finished design, is fundamentally important for a good and lasting design, the inevitable question arises. There are techniques of which the pcb maker connects the aluminium or copper layer of the metal-core pcb directly to the heat-pad of the high-power LED. This technology has different brand names and probably different ways of achieving the same goal. Now back to the question. There is no question about the advantages of such a direct path for heat to flow. The question is how and how much. If a special tool for the process is needed, cost goes up. Especially for prototypes.

So what´s the plan?

My plan is to do prototypes the regular way of doing Metal-core pcb with a layer between the copper and aluminium. The copper thickness will still be 105µm. This way I will validate the design and at the same time learn from the manufactures doing direct heat-transfer MCPCB pads.
Controller design done
Juan-Antonio Søren E.P. • 12/21/2020 at 23:38 • 0 comments

Added 6amp MOSFET next to the TMC2209 stepper pins (A+/-B+/-), tied to ground. X

Added text rCAN next to CAN termination resistor. Note: The two end-nodes in a CAN network must be terminated with 120ohm resistor.
Added AP2161W (active low) to cut USB power when VIN is applied.

Ready for prototypes!
Calculating power consumption
Juan-Antonio Søren E.P. • 12/15/2020 at 23:59 • 0 comments

With the below chart, you can se the voltage drop related to current consumption. If we stay well within the 12v, we can drive the leds to their max. The max current is controlled by dimming the LED´s while monitoring current consumption, temperature and PWM.

For a string of Photo Red´s from Cree Inc. 4 leds will produce a voltage drop of 10.4 v. (If there where 5 leds on the string, we would exceed the 12v by 1v. Using 5 Led´s on a string would max them out at 1000mA. 1amp times 2,4v is 2,4watt. Driving them to 1500mA gives (2.6v x 1.5A) 3,6watt. 3.6 x 4 LED´s = 14,4watt - 2.4 x 5 LED´s = 12watt. With the Blues there is a even greater gab, since they can be driven to 2amp. The luminus RED´s on the other hand can be driven to 2amp and has a max power dissipation a 5W. (depending on cooling). With a forward voltage at 700mA of 2.35(datasheet) the voltage drop at 2amp is 3.35, looking a below image (source). 3.35 x 5 = 16,75, so well above 12v limit. But then again, this is full on 2amp per LED, which will generate heat. Since this concept tries to explore on how to use this excess heat, the heat is somewhat welcome, but generating that heat, we might as well make the most of it. At 1.5amp the drop is around 3v, so on a 12v string with 4 LED´s, it will not go higher. Something to take into account when choosing LED´s.

Here is where it gets interesting. Below we have the radiant flux output of the Cree´s. This looks nice and well distributed over the 2amp area which is max for the Blue. So at 700mA the Luminus chart is 100% and the Cree´s is 100% at 350mA. That a pain in the blibinglyblib. How should we compare. The graph looks pretty linear in both cases....... hmm.

Cree red (XPGDPR-L1-0000-00G01) has a min 525 flux(mW) at 350mA. So at 700mA, looking at below graph, it should be 200% = 1050mW flux.

Luminus red (SST-20-DR) has depending on which flux bin up to 990mW @ 700mA. In the low end of their bin it is at 790mW, which is strange becouse that is also seen in the mouser part. Maybe that is why the SST-20 has a lower price tag. I guess the V in the product name implies the bin (SST-20-DR-B120-V660). If we say the V type is on avage 810mW at 700mA. That is quite the difference. 1050 for the cree top line and 810 for the Luminus low end @700mA. This difference is what the price reflects.

There is the calculated output difference in "brightness". But note it is relative.

Anyways, to sum it up. 14,4 watt @1500mA using 4 LED´s on a string. times 8 strings on each controller channel = 14,4*8 = 115.2 watt. 115.2 watt is around 10 amp @12v