A Detailed Look into the Mars Hydro MH-SP-250
Let’s take a look at Mars Hydro’s SP-250 LED Fixture. The following is divided into the following sections:
- Introduction
- Shipping and Delivery
- Specifications (OEM specification claims)
- Construction
- Our Measurements
- Discussion (comparing the supplied specification and marketing to our measurements)
Introduction
The LED lighting industry is something of a minefield with plenty of semi-accurate / semi-relevant information. It’s not entirely the manufacturer’s fault, mind you. Traditional lighting metrics were simply not designed to consider the needs of the horticulture industry and the industry standards associations have been slow to catch on. In many cases, the traditional metrics are next to useless. As such, metrics are evaluated under test conditions that when otherwise measured in the real world end-up showing a significant amount of variation and disappointment depending on the application. Or, metrics are provided that have little relevance towards horticulture that, rather, have been traditionally used for comparison purposes for lumenaires. The lumens, for example. To make things worse, because of this mish-mash of metrics and standards, some vendors in the space have opt’ed to conflate or mislead consumers by cherry picking metrics that look “good” or “go big”.
On the other-hand, the situation has been steadily improving over time with some vendors that specialize in the horticultural space doing their best to eliminate the cruft. Rather, they concentrate on the metrics that are most important to growers. Metrics that can be reliably reproduced even under varying conditions. This results in the customer knowing what they are getting. Rightfully so, these fixtures tend to be rather specialized and are typically pricey. The vendors that have followed this practice have become market leaders in their space.
Because of the confusing landscape of LED specifications and metrics, educated consumers have become something of LED lighting snobs and will carefully scrutinize any new vendor claims. Personally, in the past, I’ve preferred to concentrate on the ready-to-go “semi-pro” fixtures from the likes of Fluence Bioengineering, Heliospectra, P.L. Light, OSRAM, and their ilk. Their numbers tend to be reproducible on the ground. This builds trust.
And, for good reason. Light is a primary input into a plant and, as such, I have had little regret in ponying up a significant amount of coin to purchase reliable fixtures (well, maybe a little bit of regret). Fixtures from these vendors have been traditionally engineered and have proven to withstand the rigors of a growing environment. These fixtures have been designed for high efficiency through the utilization of the most modern LEDs available. They have been designed to safely operate for long periods around us ham-fisted personnel.
This brings us to Mars Hydro. Historically, Mars has produced fixtures in the “blurple” category of lights. “Blurple” being a nickname given to fixtures where the vast majority of the light output is concentrated in the blue and the red spectrum. This produces a very purple hue with little balance overall.
While plants may grow fine, such unbalanced spectra just doesn’t seem natural. Add to that the numerous studies that suggest there’s something much more to it than simply blue and red.
The newest offering from Mars, however, are broad spectrum with a radically different engineering effort when compared to their prior offerings. They’ve offered up interesting features and more thorough specifications to include information that tends to be useful in horticulture applications.
Night and day. They seem to be listening to their customers needs. I’m intrigued and have purchased a unit.
Let’s take a closer look at the MarsHydro MH-SP-250 and see how she stacks up.
Shipping and Delivery
The fixture was well packaged using expanded polypropylene foam all around. Wooden slats glued to the foam was included to protect the LED assembly.
They aren’t fooling around here. No styrofoam to be found anywhere:
Included in the package are a couple of captive hangers and ratcheting carabiners. While the hangers would be expected, the addition of carabiners are a nice touch:
Also included was a single page lamp specification.
I don’t know what it is. First perceptions matter I guess. They’ve taken some care in thinking about how this is important.
Having distributors located at strategic locations seems to help Mars to get a unit to you quickly, in a matter of a week in my case. They even contacted to let me know that shipping would be delayed by a day due to the Labor Day holiday in the US. Can’t recall the last time that occurred… Very nice of them…
Specifications
The following are the manufacturer’s specification for the Mars Hydro SP-250 as taken from the included specification guide:
Dimensions and Weight (click to expand)
Length: 42.52 inches (1080 mm)
Width: 3.54 inches (90 mm)
Height: 3.15 inches (80 mm)
Weight: 8.68 lbs (3.935 Kg)
AC Power Consumption (click to expand)
Operating Voltage: 100-277 VAC
Typical Current Draw:
1.930A @ 120 VAC,
0.9578A @ 240 VAC,
0.8387A @ 277 VAC
Operating Environment (click to expand)
Temperature: 5 - 104 F (-15 - 40 C)
Orientation : LED emission facing down
Spectrum (click to expand)
Ultraviolet : 380 - 410nm
Blue
Red
Deep Red
IR : 730-740nm
White : 3000 - 3200K & 6000-6500Khttps://www.mars-hydro.com/media/wysiwyg/MarsHydro_SP250_2x4ft_coverage_full_spectrum_high_par_1.jpg
Lifetime (click to expand)
LED expected lifetime : > 50,000 hours
LED expected output : > 90% at 50,000 hours
Warranty : Limited 3 year
Construction
The heatsink design is impressive. They’ve opt’ed to utilize relatively heavy 22 gauge aluminum for the fins and a design where each fin interlocks with each other fin and to the outer casing. This creates a solid and rigid structure.
The gauge is at least as comparable to some of the other OEM designs that I’ve seen (and own) that utilize a similar heatsink form factor. The interlocking design of the Mars heatsink is much better on this design, though. No issues on the construction here. We’ll check the operating temperatures a bit later…
I don’t know how they bonded the fins to the base but it looks fairly skookum (thank you AvE). I’m not sure if that’s a paint or a galvanized coating on the base between the fins:
Cable ingress:
Nice and proper nylon washers in the right places:
Weather / Ingress protection / IP65
Mars Hydro claims this model has an IP65 rating. What this denotes is that the assembly has been tested for protection against and to safely operate in a specific environment. The two digit number “65” indicates the level of protection and follows the following format:
(6) No ingress of dust; complete protection against contact.
(5) Water projected by a nozzle (6.3mm) against enclosure from any direction shall have no harmful effects.
This is a nice feature potentially making this model useful in environments with hired personnel and greenhouse like conditions. The home hobbyist and DIY’er may scoff at this feature as being useless to them while others that have an eye towards safety will find this feature comforting against the occasional misdirected water spray.
Conformal Coating
The LED PWB has been conformally coated by Mars Hydro. Conformal coat simply means that a protective substance is layered onto the PCB and the components after assembly. This has several distinct advantages including the protection against moisture damaging the electronics.
This is what the coating looks like from an angle:
This is a nice coating and they’ve done a great job in application. Although, this is the first time I’ve come across a conformal coat quite like this. It is soft and elastic and has the feel of a silicone resin / siloxane material:
Liquid Tight Fittings
The interconnects between the mains supply and the interconnects between the power supply and LED arrays are all spliced using liquid tight fittings.
These are not socket/plug fittings but rather splice fittings where cable terminations are screw clamped into place.
These splice points will allow you to extend cabling with a similar diameter cable without having to cut into the OEM cable. The splice fittings are not waterproof but are instead “water tight”. This type of fitting should be more than sufficient to meet the manufacturer’s IP-65 specification. These are a nice feature.
FWIW, Mars Hydro did tin the wire termination with solder which shows good practice and attention to the details that are typically hidden from sight.
Here is a photo of a temporary splice extension that is easily undone for the DC power measurement detailed later:
Power Supply Ingress Rating
The included Meanwell ELG-240-36A is rated by the manufacturer to IP65.
Power Supply
The power supply utilized for the SP-250 is a Meanwell ELG-240-36A. Meanwell has been well vetted in this space.This would be considered a quality power supply.
One interesting item to note is the listed output power capacity for this supply. The label indicates that it is capable of delivering 180 Watts from 110VAC sources and ~240 Watts from > 200VAC. We’ll circle back and look at this in more detail in the discussion section.
Dimming
This supply has a manually adjustable dimmer control accessible from bottom side of supply.
LED PWB Construction
Without taking the unit apart, the PCB is likely an aluminum core laminate which would be typically used in high power applications (such as this). Aluminum core PCBs improves the movement of heat away from the LEDs and over to the heatsink. A white solder mask is applied to the finish which is a wise choice due to it’s relfectivity characteristics.
There are a few discrete passive components on the “top” side of the PCB. Namely, 0 ohm resistors. I do not know if there are any additional components located on the “bottom” side of the PCB at this time as I didn’t want to fully disassemble the fixture. It would be interesting to do a full tear down but I’d like to utilize this lamp. Perhaps in a future episode.
The amount of solder paste (solder) used to reflow the components is likely sufficient although, in this case, there is not enough solder applied to fully wet the copper pad. That doesn’t necessarily indicate a flaw as the science behind making a reliable joint can be counter-intuitive particularly for fixtures that undergo reoccurring hot/cold cycles (thermal stress). It takes a certain amount of tuning between the manufacturing process and stress testing to get the ratio dialed in. Too little or too much can result in stress cracks (eventually leading to intermittent connections). I’m assuming they’ve tuned their process for reliability.
Overall the PCB reflow looks clean and modern.
Let’s turn her on:
When looking to determine which Epistar LEDs were utilized, we can try to catch a glimpse of the individual die and compare this to the manufacturer’s data.
I didn’t spend much time looking through the datasheets comparing the die in the above color pallete photos and, as such, was not able to find exact matches for most of these on Epistar’s publically facing website. That doesn’t mean they don’t exist, that the datasheets show accurate die diagrams, or that these aren’t custom / unlisted. If anyone would like to dig in or if Mars would like to share the info, it would be interesting to know which of the various Epistar devices are being utilized.
Measurements
AC Power Consumption (no dimming)
Measurement Instrument : Fluke 43B Power Quality Analyzer (click for details)
Instrument : Fluke 43B
Type : Multi-meter
Measurement Range: Voltage 5.000V to 500.0V, Current 50.00A to 500.0kA
Accuracy: Voltage ±(1 % + 10 counts), Current ±(1 % + 10 counts)
Calibration Source : Manufacturer
Measurement Instrument : Pico TA189 Current Probe (click for details)
Instrument : Pico TA189
Type : Current Probe
Measurement Range: 0-30A
Accuracy: ± 1% of reading ± 2mA
Calibration Source : Built-In
DC Power Consumption (no dimming)
Measurement Instrument : Fluke 43B Power Quality Analyzer (click for details)
Instrument : Fluke 43B
Type : Multi-meter
Measurement Range: Voltage 5.000V to 500.0V, Current 50.00A to 500.0kA
Accuracy: Voltage ±(1 % + 10 counts), Current ±(1 % + 10 counts)
Calibration Source : Manufacturer
Measurement Instrument : Pico TA189 Current Probe (click for details)
Instrument : Pico TA189
Type : Current Probe
Measurement Range: 0-30A
Accuracy: ± 1% of reading ± 2mA
Calibration Source : Built-In
Power Consumption (click to expand)
As measured at the output of the Meanwell power supply:
Calculated Supply Conversion Efficiency: 92%
Temperature (no dimming)
Measurement Instrument : Fluke 80T-150UA Universal Temperature Probe (click for details)
Instrument : Fluke 80T-150UA
Type : Temperature Probe
Measurement Range: -58 to +302 °F
Accuracy: ±1.8°F from +32 to +212°F
Calibration Source : Manufacturer
Measurement Instrument : Flir A35 Thermal Camera (click for details)
Instrument : Flir A35
Type : Thermal Camera
Measurement Range: -25°C to 135°C (-13 to 275°F) / –40°C to 550°C (-40 to 1022°F)
Accuracy: ±5°C (±9°F) or ±5% of reading
Calibration Source : Self / Manufacturer
Operating Temperature
Beginning Surface Probe Measurement: 77.4°F ()
Power supply case at 1.5 hours: Surface Probe 129.5°F ()
Heat sink fin at 1.5 hours: Surface Probe 116.3°F ()
Hotspots: Some regions of LEDs show hotspots (click to expand)
Hotspots, false color images, @1.5 hours non-dimmed
Thermal Image of Operating Assembly (click to expand)
Fixture thermal image, false color image, @1.5 hours non-dimmed
Lighting Metrics
Spectral Power Distribution (SPD)
Measurement Instrument : Stellarnet CXR-SR-100 (click for details)
Instrument : Stellarnet CXR-SR-100
Type : Spectrometer
Bandwidth : 220 to 1100 nm
Resolution : 4 nm
Optical Fiber : F600 VIS/IR
Sensing Head : Cosine Corrected Adapter CR1
Calibration Source : Stellarnet SL1-CAL (300-100nm) Tungsten-Halogen Lamp
18 inches from fixture, open air, center spot, 30 minutes to stabilize (click to expand)
Center Point, Open Air Measurement:
Spectrometer and Quantum Sensor Cosine Heads:
Spectrometer Electronics:
Spectral Distribution :
Blue(400 - 500nm): 15.4872% Green(500 - 600nm): 43.8039% Red(600 - 700nm): 40.7089% Total :100%
UVB(287-320nm): 0.00759645% UVA(320-400nm): 0.140558% Violet_Blue(400-475nm): 13.1032% Cyan_Green(475-550nm): 17.2152% Green_Yellow_Red(550-700nm): 65.0914% FarRed_NearIR(700-850nm): 4.44204% Total :100%
Radiant Energy and Ratios
The following metrics details the measured radiant energy 18 inches from the fixture, open air (no nearby reflective walls), center spot (at the center of the fixture), after allowing 30 minutes for the fixture to stabilize:
Integral radiant (400-700nm): 102.213 W/m^2
Integral radiant (350-840nm): 106.0 W/m^2
Lumens (m^2) : 33534.23
Spectrometer PAR (400-700nm): 484.463 umol / m^2 s
Quantum Sensor PAR : 451.6 umol / m^2 s
YPF (360-760nm) : 433.314 umol / m^2 s
YPF/PFD: 0.89
PSS: 0.85
DLI index [12 hours] : 20.93
PAR Max :1.34342 @595.073 nmOutput Stability
Output power as measured with the Apogee Quantum Sensor over an ~80 minute period from power-up shows a small amount of variation of ~2% as the unit heats up. Measured 18 inches from fixture, open air, center-point.
Color Quality
The following graphs details how the human eye will perceive colors that are illuminated by the fixture. This has little to do with the quality of light as perceived by the plant but rather how easy it is for humans to discern colors or how accurate the colors in a photograph under illumination will appear.
Chromaticity 3750K (click to expand)
CCT: 3750
Chromaticity Coordinates: (x=0.39079, y=0.37253)
Dominant Wavelength: 601.5nm
Purity: 29.49%
PAR Map
Measurement Instrument : Apogee Instruments SQ-250 (click for details)
Instrument : Apogee Instruments SQ-250
Type : Quantum Sensor
Bandwidth : 389 to 692 nm ±5 nm
Resolution : 0.1 µmol*s / m^2
Sensing Head : 2PI Cosine Corrected
Calibration Uncertainty : ±5%
Calibration Source : Manufacturer Calibration
Source Correction Table :
Not measured.
Manufacturer’s Warranty
Specification notes a limited 3 year warranty.
Number of LEDs
Radiant Energy
With Epistar, a PPE greater than two is still a very good number.
and bloom, turn “growth” or “growth” and 
“bloom” on for veg 
UNITED STATE:
