LED Grow Lamps ? A Breakthrough or a Gimmick? Part 3

LED Grow Lights

PRAKASA 300W BULB UNIT - In parts 1 & 2 of this series we introduced our new Li-Cor Quantum meter and we talked a little bit about why this expensive but precision piece of kit is the correct one to use for grow lamp testing and comparisons.

With all that out of the way, we will now move on to introducing our test set-up and our experimental procedure:

For this test, we need an environment that is as close to a real-life set-up as we can get. We therefore decided to use a quality 1 metre x 1 metre grow tent which is a one of the popular choices for a hobby grower using grow lamps in the 250 Watt to 600 Watt range. Our shop staff would generally recommend a 1 metre square tent for someone wishing to use a 400 Watt HPS grow lamp. This size of tent is clearly a good choice given the range of lights that we plan to test. Easy Rolls were installed to make an easy job of raising and lowering the lights.

It would seem to be fairly obvious, even with just a casual glance, that the grow lamp is only producing a high intensity of light directly underneath the centre of it. This was a little surprising to me because the impression I got from just using my eyes was that the light intensity seemed to be much more even than this.

In fact, I thought I must have made some kind of error in my measurement taking. So much so that I ended up rechecking my results. However, I had made no mistakes, the results really were as shown in the above graph.

To decide on the next height, I experimented a little to try to find a good balance between spread and intensity. It was my intention to find that ideal height that gave enough intensity at the centre that would give good growth, while still illuminating the edges adequately.

I found that the best height that achieved the most even spread was 43cm.

At 43cm, the graph does look somewhat flatter. The peak in the middle is most definitely still there, however, the average spread across the tent is much better.

I would have to say, that despite my hopes for this lamp, the results are somewhat disappointing.

I spent quite some time testing to see if I could find a height at which the light intensity at the edges of the tent was satisfactory. In this 1m x 1m tent the maximum intensity I could find at any point the edges was 270µmol. This measurement was actually found at the 43cm height in the graph shown above.

270µmol would not generally be considered to be a fantastic intensity for excellent plant growth. It may be just about adequate for young or vegging plants. However, during the flowering/fruiting period you are going to need at least 2 to 3 times that for a really nice size crop.

Remember, this lamp consumes 300 Watts, and costs £300 or thereabouts. I seriously expected it to have a much better spread. The intensity of light directly underneath is fine but anywhere else in tent there is a definite shortcoming.

At the moment, I have not completed my experiments with other types of light source. In the following articles in this series I will be testing and measuring the following lights and producing similar graphs for comparison:

  1. 200 Watt CFL
  2. 216 Watt T5 Maxibright LightWave
  3. 300 Watt Gavita Plasma
  4. 400 Watt HPS
  5. 250 Watt and 400 Watt MH

It will be interesting to see how the Prakasa lamp stands up to comparison with these other types of light source. In particular, I will be very interested to find out how the spread of light stands up against the standard growers favourites: the Maxibright LightWave and HPS lights.

As always, the proof is in the pudding, and while I am spending time testing the other types of lamp, I shall also be growing an actual real, live plant under the Prakasa to see just what can be produced.

Watch this space.....!

Apart from that, the main other piece of equipment is a tape measure for accurate measurement of the distance between the lamp and the sensor. Armed with that and lots of paper and a pencil, we are ready for the actual testing which will we will be starting in the next part. We will begin our testing with the Prakasa 300 Watt LED grow lamp:

The Prakasa 300 Watt LED grow light is not a cheap piece of equipment. However, it is representative of what a serious hobby grower might consider buying rather than a 250 Watt or 400 Watt HPS grow lamp. Prakasa have certainly made a nice job of making it. It contains the following LEDs:

  •        Deep Red 660nm: 8 x 3w LEDs + 19 x 5w L
  •        Red 630nm: 13 x 3w LEDs + 33 x 5w LEDs
  •        Orange 610nm: 12 x 3w LEDs
  •        Blue 460nm: 8 x 5w LEDs
  •        White 15000-20000 Kelvin: 6 x 3w LEDs + 6 x 5w LEDs
  •        UV 410nm: 2 x 3w LEDs
  •        IR 740nm: 1 x 3w LEDs

The Prakasa emits a good range of different wavelengths and would seem to be well thought out. Cooling fans on the top of the unit ensure that the LEDs do not overheat which could affect their 50,000 hour lifespan. The manufacturer claims that this grow lamp can cover an area from 1 – 2.5 metres squared and gives out light equivalent to that from a 600 watt HPS. This is quite a claim and we shall enjoy finding out if they are right!

Before signing off this part, we switched the unit to show you the inside of the grow tent bathed in an eerie pinky-purple light!

In part 4 of this series we will be beginning the actual testing and bringing you some juicy data! 

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