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LED Lamp Modification

A simple refit of the internals of the lamp housing can be undertaken to make use of LED lights, with significant power reduction, temperature rise and long term reliability.

 

Fig 6. LED strips

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 6 12V 12W LED Strips

 

Some 12V 12W LED strip lamps were purchased (http://www.dealextreme.com/p/12w-3500k-800lm-warm-white-led-emitter-metal-strip-12-14v-80310). These are operated from a 12V power source and are as bright as the 18W fluorescent tube. They emit a ‘warm white’ (3500K) light and are able to be bolted directly to the internal channel for heat sinking. One of these LED strips was used in place of each fluorescent lamp, each drawing only 700mA from a 12V switching power source. This is a total of 16.8W for two LED strips, less than half the power of the existing 2x18W fluorescent fitting.

 

Fig. 7 LED PSU

 

 

 

 

 

 

 

 

 

 

 

Fig. 7 LED Power Supply fits where the ballast was

 

The power supply used is a 12V 30W LED driver imported from China by Victoria ECO LED lighting. These fit neatly into the channel where the electronic ballast was previously fitted. Since there are also fewer wires going through the holes from the lights to the power supply, there is more ventilation for the centre channel.

The images in fig 8-9 show the internal refit for LED operation. Fig 10 shows the LED (right) and the fluorescent (left) in operation together, showing similar light brightness output.

 

Fig 8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig 8. LED strips fitted in place of 18W fluorescent lamps

 

Fig 9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 9 View of internal components with LED strips and LED PSU fitted

 

Fig 10

 

 

 

 

 

 

 

 

 

 

 

Fig. 10 Wall lamps using LED strips in place of fluorescent tubes


The same temperature measurements were taken as for the original fitting, ambient, external case and internal channel air temperatures and graphed over a 2 hour period. The graph is shown in fig 11.

Fig 11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 11. Graph showing significantly reduced temperature rise for LED fittings

 

The temperature rises are significantly lower, as shown in the table below.

Location

Rise above ambient (OC)

Outer front casing

11OC

Inner channel air temp

16OC

 

The power supply produces an insignificant amount of heat, and most of the heat is produced by the LED strips bolted to the internal channel, as can be seen by the small difference in temperature between the external case and the internal enclosure.

The cost of the LED strips ($15 each) and the power supply ($20) comes to $50 for the LED re-fit. As spares, the cost of the fluorescent lamps ($8 each) and the ballast ($30) comes to $46, so it is not significantly more expensive, however the anticipated lifetime of the LED wall lamp is significantly greater given the reduction in temperature and the longer lifespan of LED lamps.