Background : White LED Lighting
I developed these grow lights alongside the bike lighting systems as they have many parts in common. As i found a solution to the problem in one system it in turn solved a problem in the other.
Grow lights for seeds and seedlings allow a commercial grower and amateur gardener to germinate seeds and bring on seedlings much earlier than they would otherwise be able to using only natural light. Commercial grow lights use high power bulbs usually with a power consumption of around 400W. They provide a good spectral output but they are expensive to run and have to be handled carefully as they are known to shatter firing glass all around. They have one major disadvantage in that they also generate a lot of heat. There is a balance to be achieved setting them up. Too far from the seedlings and the light intensity is wasted and the operating cost is higher than it should be. Too close and the seedlings get burned from the excessive heat. Usually the manufacturers recommend that the lamp is at least 600mm from the seedlings.
With the availability of low cost high power LED lamps i decided to investigate the possibility of developing a grow light that would be less expensive to operate, was low heat output and would be modular in nature to allow it to be modified for different applications. e.g. large and small propagators, different sized seed trays etc. Assuming 5W LED bulbs produce the equivalent light output of a 25W of bulb, 16 LED bulbs would be required to produce the equivalent light output from a 400W grow light. However LED bulbs produce much less heat so can be positioned much closer to the seedlings. This in turn means that the number of LED lights required to obtain the same light intensity at the seedlings can be greatly reduced. The advantage of the LED lights is quite clear, reduced heat, reduced power consumption and thus operating cost and reduced operating space.
The modular system described below uses readily available low cost components. The LED Lamps are 12V AC/DC types readily available in shops or on-line. The LED lamps are housed in 40mm plastic plumbing parts which are a mixture of push and screw fit. The wiring and connectors are used in automotive electrical systems so are able to operate reliably in the extreme of temperatures and humidity present in a greenhouse. The plumbing parts and wiring can all be modified to meet custom needs but i have chosen some standard lengths to meet my needs in the greenhouse and with propagators.
The lights are powered from converted recycled ex-PC Power Supply Units. Click here for more details.
Grow lights for seeds and seedlings allow a commercial grower and amateur gardener to germinate seeds and bring on seedlings much earlier than they would otherwise be able to using only natural light. Commercial grow lights use high power bulbs usually with a power consumption of around 400W. They provide a good spectral output but they are expensive to run and have to be handled carefully as they are known to shatter firing glass all around. They have one major disadvantage in that they also generate a lot of heat. There is a balance to be achieved setting them up. Too far from the seedlings and the light intensity is wasted and the operating cost is higher than it should be. Too close and the seedlings get burned from the excessive heat. Usually the manufacturers recommend that the lamp is at least 600mm from the seedlings.
With the availability of low cost high power LED lamps i decided to investigate the possibility of developing a grow light that would be less expensive to operate, was low heat output and would be modular in nature to allow it to be modified for different applications. e.g. large and small propagators, different sized seed trays etc. Assuming 5W LED bulbs produce the equivalent light output of a 25W of bulb, 16 LED bulbs would be required to produce the equivalent light output from a 400W grow light. However LED bulbs produce much less heat so can be positioned much closer to the seedlings. This in turn means that the number of LED lights required to obtain the same light intensity at the seedlings can be greatly reduced. The advantage of the LED lights is quite clear, reduced heat, reduced power consumption and thus operating cost and reduced operating space.
The modular system described below uses readily available low cost components. The LED Lamps are 12V AC/DC types readily available in shops or on-line. The LED lamps are housed in 40mm plastic plumbing parts which are a mixture of push and screw fit. The wiring and connectors are used in automotive electrical systems so are able to operate reliably in the extreme of temperatures and humidity present in a greenhouse. The plumbing parts and wiring can all be modified to meet custom needs but i have chosen some standard lengths to meet my needs in the greenhouse and with propagators.
The lights are powered from converted recycled ex-PC Power Supply Units. Click here for more details.
The wires are made from automotive electrical wiring. The connectors at each end are 6mm male and female 'spade' connectors. The female connectors are fully insulated. There is one male and one female connector at each end of each wire.
Each bulb is connected to the supply via a GU5.3 MR11/MR16 bulb holder. At the end of each of its wires there is a fully insulated 'piggy back' spade connector. this allows a chain of lamps to be connected.
In an early prototype i used terminal block to wire the lamps together but i found this very 'fiddly' to connect together and the temperature variation tended to cause the terminal block screws to come loose.
This picture shows some individual wires with connectors before they were cable tied together to create the interconnect harnesses.. The middle group shows a collection of interconnect harnesses and at the bottom is a lamp bulb holder with the 'piggy back' connectors.
In this picture the top harness shows how the length of the wires can be extended by connecting two of the harnesses together. The lower harness shows two of the standard harnesses and an LED bulb connected together. This forms a basic 'T-Harness'.
Here a basic T-Harness has installed into a plumbing T-piece. The harness interconnections are inside the plastic body.
Here a 90 degree end piece has been added to end the chain, but one or more T-pieces could have been used.
This picture shows a larger assembly consisting of two T-pieces and and end piece with three LED bulbs installed.
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Here two lamps have been daisy chained. This can be repeated to form a chain of the required number of lamps.
Here a lamp has been installed into the body of the T-Piece , a spacing pipe has been added and the next T-Harness has been connected to the first.
Here the assembly has been completed. Two different bulbs have been used. One 4W bulb which consists of 3 high power LED's and another which is assembled from 30 SMD LED's.
The flexibility and adaptability of the system is demonstrated here. The joints between the sections can be easily rotated so that light can be directed to exactly where it is needed.
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Here a small chain of lamps was set up to sit on top of a propagator to help germinate begonia seeds that need light to do so. The lights are close to the seeds and they sit on top of the propagator. The lights can be moved so that they are directly above the seeds and seedlings that require it.
This is possible because the LED's generate very little heat compared to an equivalent halogen spot lamp. If halogen lamps had been used the plastic bodies housing the lamps and the propagator cover would melt due to the heat they generate!
Below are a number of pictures which show the lighting in use in the greenhouse over the past few years. Because the lighting is very light weight it can be suspended from the greenhouse frame above the plants that require the light.