Happy thanksgiving, everyone!
Recently, I needed a grow light for a relatively small grow area (the plastic container shown above). COB LEDs are great for a large area with enough vertical space. I could have used smaller COB LEDs, but I thought something like Philips XF-3535L (previous post) would be great. After comparing quite a few LED linear modules, I determined that Samsung H series has the best performance for the price at this moment. Indeed the efficacy is amazing, even higher than typical COB. But it does cost a bit more per light output than COB. So here is a brief report of this build.
Samsung H series was announced in summer 2016, and it became available in the US in October 2016 (link to data sheet). It is similar to Philips XF-3535L, which I mentioned previously in this post. However H series is newer, and the efficiency is quite a bit higher. In the previous XF-3535L post, I listed the advantages and disadvantages of the linear modules, and these apply to Samsung H series, too.
Comparisons: Samsung H series comes in 3 different length; about 1', 2', and 4'. Basically 2' version is same as 2x 1' version connected in parallel. Here are some relevant specs, and a comparison to XF-3535L:
|Model||size (mm)||luminous flux (lumen)||efficacy (lumen/W)||nominal current (mA)||Vf||watt||temp. Tc (C)||price($)|
H series, Digi-Key seems to be the only vendor in the US.
A couple things to note from the table above. The specification of Philips XF-3535L is measured at an unrealistically low temperature of 25C while H series is measured at a more reasonable Tc=50C. 25C is about the room temperature and most LEDs operate at much higher temperature. So actual output (luminous flux) and efficacy of XF-3535L is lower than the specified values in the table. The price per lumen as well as lumen per length is fairly comparable between H-series and XF-3535L. But due to much higher efficacy of H-series, the power consumption (watt) is much lower with H-series.
At this moment, there is not much reason to choose XF-3535L over H-series. I should note a couple differences between them. XF-3535L comes in the flexible tape form while the base of H-series is rigid. XF-3535L has double sided tape, so it is slightly easier to attach to heatsink. With H-series, I used thermal adhesive (a bit messy, but easy). Finally, the XF-3535L is narrower in width, so it may be good for some applications.
- LED: 4x Samsung LT-H282D 1-foot module, 4000K, 80CRI, SI-B8T05128HUS ($10.93 from Digi-Key)
- Driver: Meanwell APC-25-500 (data sheet, about $10.10, link to Octopart search)
- heatsink: Aluminum 3/4" C channel (about $13 for 8' from HomeDepot)
- FUJIK 50ml Silicone Thermal Adhesive (link1, link2 about $7, but you can find it cheaper in smaller volume on eBay).
- 2-prong AC-plug
- solid core 18-24AWG gauge wire (something like this: $14.99 for 100ft)
- Wago Connector, Wire-Nut (something like this), or soldering to connect the AC-plug to the driver.
Digi-Key gives volume discount ($7.84 ea for 25 pieces or more), so I got 30 LED modules. I'm going to make several fixtures including light for planted aquarium. For the drivers, I got 2 kinds: APC-25-500 to drive 4 modules, and APC-16-700 to drive 3 modules. I'm using this for Pygmy Drosera, so it requires fairly high amount of light and I'm using four modules for this build. I'll talk about the different driver options later.
|Arrival of components. The larger driver on the left is APC-25-500, and the right driver is APC-16-700.|
|The back and front of Samsung H series LT-H282D is shown below the ruler. The larger driver on the right is APC-25-500, and the left driver is APC-16-700.|
I cut the aluminum C-channel into an appropriate length with a hacksaw. Then I drilled 2 mounting holes at the ends. The LED module was attached to the C-channel by thermal adhesive. I spread the adhesive as thin as possible with my finger on the back of the LED module. This is not the epoxy kind, so the LED module can be removed. from the heatsink Thermal conductivity of the silicone thermal adhesive may not be as great as thermal compound, but I think it is sufficient. Each module is dissipating less than 2.5W of heat. Even without the heatsink, the LEDs become just warm and not super hot.
After the adhesive dried over night, I mounted 4 modules to the lid of the plastic container with #6x1/2" machine screws.
Since I wanted to have some space between the lid and the heatsink for better cooling, I used three #6 washer per screw as the spacer.
Then I connected the modules with 18AWG wires. I happened to have 18AWG, but thinner 24AWG is good enough. The data sheet specifies solid core, so I'm not sure if stranded wires are usable with this connector.
After stripping 8mm of insulation from each wire end, I pushed the wire into the connector. If you make a mistake, you can remove the wire by pushing the right half of the connector (the side opposite to the wire entry) with a tip of a screw driver, and gently pulling the wire. Each module has 2 sets of connectors. At each end of the module, there is + and - connectors (see below). + connector of one end is connected to the other + connector of the other end within the LED module. - connectors are connected, too. This is convenient for parallel connection of LED modules.
From the photo above, it is probably difficult to understand how they are connected, so here is the simplified diagram of the connection. LED1 and 2 are connected in parallel, and LED3 and 4 are connected in parallel. Then these two parts are connected serially. For some basic info about connecting multiple LED modules to a single driver, take a look at my previous post.
I used the 2 screw holes of the driver to attach the driver to the top side of the lid of the plastic container. The driver does generate a little bit of heat. So it is better to put it outside of the grow space. Then I connected the AC plug to the AC input of the driver. Brown wire of the driver is connected to live (hot), which is the smaller blade of the AC plug, and blue is connected to neutral, which is the larger blade. This driver doesn't require the connection of the ground (the stick/pole of the AC plug).
That's all, it is super simple! Time to test out. The C-channel acts as a reflector, and the narrower beam angle is achieve. The photo below shows the beam pattern.
Now the lid fixture is put on top of the container. Just to see how much heat accumulate inside, I kept the lid completely closed for a while. Surprisingly, the inside temperature was raised only 5F above the ambient temperature. This backs up the claim of super high efficiency. I made a spacer (not shown in the photo) so there is a bit of space (about 1-2cm) between the lid and container for air exchange.
|This container is Hefty 66qt. 23.9"Wx16.8"Dx13"H.|
This is one of the pygmy Drosera inside the container. Those have been growing under very weak light, and I hope that they will do better with the much stronger light.
|Drosera dichrosepala ssp. enodes from Scott River. Catalogue #10a of Drosera Gemmae.|
I measured photosynthetic photon flux density (PPFD) at 30 cm (1') from the LED. For the measurement of 4x Samsung H, I measured at the very middle of the fixture, so it wasn't directly below one of the module. For the others, I measured PPFD directly below the middle point of the linear LED module. For the 1x Samsung H, I measured each of the four modules, and took the average (only a small variation among 4 modules). For the watt, I measured it with 3 International P4460 Kill A Watt EZ. So it include the electricity wasted by the driver. For the wattage of 1x Samsung H, I simply divided the total watt (27W) from the fixture with 4 modules by 4.
|model||PPFD (µmol m-2 s-1) at 1'||footcandle||watt||power factor|
|4x Samsung H, 4000K, CRI 80, SI-B8T05128HUS||155||1010||27||0.58|
|1x Samsung H, 4000K, CRI 80, SI-B8T05128HUS||52||333||6.8||0.58|
|1x Philips XF-3535L, 4000K, CRI 80, L235-4080AMLF5WAD0||110||655||22.7||not measured|
In the plastic container above (Hefty 66qt, 23.9"Wx16.8"Dx13"H), the plant is about 10" from the LEDs. It is getting 200 µmol m-2 s-1 in the center and 170 µmol m-2 s-1 near the edge (1439-1050 footcandles). For the high light carnivorous plants, it could use a bit more, but I'll see how the pygmy Drosera will do. In the last year, I was using less than half of this, and they grew ok.
Alternative driver configurations:
- For smaller fixture, 3 modules can be connected to a single APC-16-700 (about $6, data sheet). With 3 modules, it would be good for low to moderate light orchids. At 1' distance, I measured 44 µmol m-2 s-1 and 28fc from 1 module. It consumes 18.3W and power factor of 0.57. You can use parallel connection like this:
- APC-8-250 ($5) can drives 1 LED module. But it isn't an economical choice. The driver which can drive 3 modules is only $1 more expensive.
- APC-35-700 ($13.44) can drive 6 LED modules. You make 2 parallel circuits with 3 modules each (like the figure above), then connect the 2 circuits serially.
Update (Fall, 2019): Bridgelux EB-series Gen. 3 is available (data sheet for 24mm width version, data sheet for 12mm slim version). It achieves 200lm/W at the nominal current. It comes in 1', 2', and 4' versions. I used 5700K Gen. 2, which had 24mm width for my reef aquarium light. The 24mm width version can be attached to the outside of Aluminum C-channel, but I would prefer the slim version so the C-channel wall limits the light escaping to the side. This is probably the model I would use instead of Samsung at this moment.
Update (March, 2019): Samsung announced Horticultural Linear LED modules (data sheet). It achieves slightly higher photosynthetic photone efficacy (PPE, 2.74 μmol/J @1200mA, Tc=25C) by combining white and red LEDs. Red LEDs generally have the highest efficacy in terms of number of photons per given energy (i.e., PPE) although white and blue LEDs may have a higher efficiency in terms of emitted light watts per given electric watt (the former efficacy is more relevant for plants). This module finally became around summer/fall 2019, but it is fairly expensive ($50 for 2 feet model from Digi-Key). It comes in either 1ft or 2ft length. Also, the width (41mm) is wider than Samsung's F, Q, or H-series (18mm), so it does not fit in the cheap aluminum C-channel.
Update (Aug 25, 2017): Samsung announced Q-series (data sheet) with a slightly higher efficacy (Aug 25, 2017, see at the end of this post for the possible drivers). But softly driven F-series may be a better deal.
The efficiency appears to be about 10% higher than H-sereis Gen.3. Luminous efficacy is 203 lm/W for 4000K at the nominal current. It comes in four lengths: LT-Q282A (27.5cm), LT-Q562A (56cm), and LT-QB22A (112cm), roughly 1', 2', and 4', respectively. The nominal current are 450mA for all three models. At the nominal current, forward voltages are 11.9V, 21.9V, and 43.8V and they produce 1000, 2000, and 4000 lumen (for 4000K model), respectively.
The price is similar to H-series Gen.3. For 4000K model, the prices are $8.22, $13.26, $23.21 for 1', 2', and 4' modules respectively. The price is from Digi-key, which is the only supplier for hobbyist in the US, and the link provided is for the 4000K model. It comes in other color temperature (3000K, 3500K, 4000K, 5000K).
For the driver, 1x APC-25-500 (about $10) can drive 4x 1' modules connected serially, 2x 2' modules connected serially, or 1x 4' module. 500mA is 10% higher than the nominal current, so the efficacy will be slightly lower than the nominal 203 lm/W. But it is still amazing efficiency. 1x APC-35-500 (about $11) can drive 6x 1' modules connected serially. For a larger area, 1x LPC-100-500 (about $23) can drive 16x 1', 8x 2', or 4x 4' modules connected serially.
Update (Dec. 2016): Samsung F-series Gen 3 (data sheet) can be a better alternative. It uses the same diodes (LM561C) as H-series Gen. 3, but they are targeted for more powerful application. So each module has 1.5x diodes of H-series. The price is only slightly higher. Even though they are marketed for a higher output, you can still drive them at the lower current to gain efficiency. For the 1' length, F-series only has a fat linear module, so it doesn't work with the aluminum C-channel I use below. But for 2' and 4' lengths (LT-F562B and LTFB22B), F-series comes in the same 18mm width. If you drive F-series at the nominal current, I'm not sure if the aluminum C-channel is sufficient as a heatsink, so you should check it by yourself.