47 replies to this topic

[Marcus B]

mobile, on 17th February 2011 - 22:22 PM, said:

Still looks too anaerobic to me. I personally would have added more drainage material. However, I wouldn't risk repotting again - just cut back on the watering to keep them damp rather than wet.

Just one little thing that I would like to clarify.  Cephs naturally grow in very anaerobic substrate.  I am told that it is extremely smelly when distrubed, such as when you wade through it get to the plants growing in those soils.  So the issue with potting mixes is not so much that they are anaerobic.  The issue is that they need the movement of water through the substrate to keep roots healthy.  

As we don't all have flowing water through our pots, increasing the movement of air helps with this issue as well, so increasing the aerobic nature of the mix is therefore necessary if the plant is to remain in those conditions long term.   Giving it plenty of water poured through the pot and low humidity will also work, but it is easier to just improve the air flow in the mix.

However, as you are in winter, reducing the watering is clearily the best option.  I tend to leave my pots sitting out of trays or in dry trays in winter so any water that they get runs straight through the pot.

[storm]

I have a question to those who grow Cephalotus of artificial light, in particular LED light.
What is the duration of illumination?
24/24 or 16 / 8 (16 light / 8 night) or some other period?

[jesse]

storm, on 18th February 2011 - 09:14 AM, said:

I have a question to those who grow Cephalotus of artificial light, in particular LED light.
What is the duration of illumination?
24/24 or 16 / 8 (16 light / 8 night) or some other period?

In summer half-year (May-Nov) I'm growing my Cephalotus outdoors.

And in winter it is growing at a 12/12 photoperiod under LEDs in a chilly room.

[storm]

Just the two of you use LEDs as lighting?
Anyone else?

[mobile]

Mine are on 13 hours/day all year round. This is for practical reasons. I know that other growers use LED lights, I think mostly the red/blue ones. I still think it's far more practical to use fluorescents at the moment. I tend to use the 3 or 6W GU10 LED lamps to spotlight 'special' plants, as it's practical to purchase these from eBay; however, building LED arrays is too much hassle for many growers who simply want to purchase something ready made, i.e. a linear fluorescent light fitting or a gullwing reflector with Envirolite type lamp.

[pmatil]

I use a couple if 5 W LED spots for my cephas. The LEDs are "cool white" and the plants love them. They color up nicely.

[mobile]

pmatil, on 20th February 2011 - 10:20 AM, said:

I use a couple if 5 W LED spots for my cephas. The LEDs are "cool white" and the plants love them. They color up nicely.

Mine colour up nicely under LED too, but they don't grow very fast.

[storm]

I think it matters what exactly are diodes.
Diodes are not cover the entire spectrum of light, they are divided into groups:


Basically, to grow plants better and to simulate as close as the light from the sun, we need three basic types of diodes - Cool White, Neutral White and Warm White.
Cool White ~4500 - 10000nm
Neutral White ~3500 - 4500nm
Warm White ~2700 - 3500nm


Unfortunately I could not find Neutral White LEDs (normal price).

[jesse]

storm, on 20th February 2011 - 15:07 PM, said:

Basically, to grow plants better and to simulate as close as the light from the sun, we need three basic types of diodes - Cool White, Neutral White and Warm White.

My Cephalotus grows with sun in my garden from mid of May until mid of November.
And it grows with two high-power LEDs in my cellar for the other 6 months.

The two LEDs are:
Cree XR-E cool-white @350 mA
Cree XR-E red @350 mA
Total lighting power = 2 watt
Lighting distance ~ 12 cm
Daily photo period: 12 hours

And this is the plant as of today (image was taken using daylight, not LED lighting):

[storm]

Have you noticed any difference in growth in the sunlight and growth in LED light?
For example, faster / slower growth?
Differences in color?

Edited by storm, 20 February 2011 - 18:14 PM.

[jesse]

storm, on 20th February 2011 - 19:11 PM, said:

Have you noticed any difference in growth in the sunlight and growth in LED light?
For example, faster / slower growth?
Differences in color?

The plant seems to recognize the 2-watt LED lighting as a weak winter light.

The plant stops developing new pitchers and develops winter leaves only.

[storm]

Have you measured the temperature of the body of the LED / spot?
Because the higher the temperature the less is the light.

[mobile]

My 6W GU10 LED spot has an aluminium vane heatsink surrounding it, which gets extremely hot if un-cooled. I have a fan blowing on the heatsink while the lamp is operating.

[jesse]

storm, on 21st February 2011 - 10:55 AM, said:

Have you measured the temperature of the body of the LED / spot?
Because the higher the temperature the less is the light.

Yes, LEDs give more light and live longer when operated at cooler temperatures.
So operating LEDs at cool temperatures is a very good idea.

But no, measuring the "junction temperature" of an LED is nothing that a hobbyist can do.
At least, I cannot.

As a hobbyist you just provide cool temperatures by operating high-power LEDs that way:
- no LED operation without proper cooling, not a single second!
- operation with "constant current" drivers, not with fixed voltage AC/DC adapters
- operation with somewhat less than the max. rated current
- purchase high-power LEDs only pre-mounted "with star" (a small hexagonal-star shaped mounting board for direct soldering)
- use a thermal compound (2-component glue, not grease-like) to fix the star mounting board on a cooling plate
- use aluminium cooling plate of about 16 cm^2 (4cm*4cm) per watt for passive cooling (without fan)
At least, this is what I do.

My Cree XR-E LEDs are rated:
cool-white ==> max. 1000 mA
red ==> max. 700 mA
I operate both at 350 mA only. But 700 mA should also be possible with just passive cooling.
If you stay below the max. current rating, LEDs keep cool even if you don't use the best type of heat sink. I.e. I glue the LEDs using thermal glue only on a simple aluminium plate for passive cooling and everything is fine. If you want to use max. current, you better use fancy heat sinks and active cooling by rotating fans to cool them, or the lifespan goes down.

The higher the temperature, the lower the light output per watt and the lower the lifespan of the LEDs.

[storm]

Would you share some pictures of LED's?

[jesse]

storm, on 21st February 2011 - 13:15 PM, said:

Would you share some pictures of LED's?

This is the my construction of the 2 Watt lighting hood for my Cephalotus:


http://www.cpukforum...a...si&img=2851

1 x Cree XR-E cool-white on star (the one on the black star plate)
1 x Cree XR-E red on star (the one on the white star plate)
Aluminium cooling plate 4x8 cm
Lighting hood = an old 1 litre icecream box

The aluminium plate is fixed to the hood with double-sided adhesive tape
The LED stars are glued to the aluminium plate with thermal compound glue (2-component).
Series connection by soldering some wires.
The unit is powered by a constant current driver @350 mA.

The twisting of the red and black wires through the holes are for strain relief, so that no force is on the solder points when pulling at the red/black wire.

This lighting hood is not an exhibition piece, it is just for overwintering the Cephalotus in my cellar.

[storm]

Why did you choose these two diodes, in particular the red one?

[jesse]

storm, on 21st February 2011 - 20:06 PM, said:

Why did you choose these two diodes, in particular the red one?

I choose LEDs "mounted on hex star" because these pre-mounted LEDs can be finally mounted with glue on a cooling plate and wired with a soldering iron by a hobbyist.

I have chosen Cree Diodes as they provide a good relation for "lumen per price" as well as for "lumen per watt".

The red one in addition to the white one is just an experiment.
All my LED lighting is experimental.

Most of my "LED plants" get light from cool-white LEDs only (no red added), but my Cephalotus gets red and white.

Edited by jesse, 21 February 2011 - 20:41 PM.

[mobile]

Red is one of the Chlorophyll absorption bands, so the plants should be able to use this more efficiently than a broad spectrum light, especially when combined with blue. My setup is somewhat simpler, using a pre-made GU10 6W LED. Note the fan used to keep things cool and efficient:





I also have a 7W Philips LED GU10 lamp, which I assume contains cree LEDs:

[storm]

This is my LED lighting...