Garage LED lighting


LED garage lightingThe garage-workshop was lit by four 200 watt incandescent lamps and two 4-foot fluorescents.   Other than the huge power draw, the light was quite yellow and produced a lot of shadows.

For some time the plan has bee to experiment with LED strip lighting for improved white light, fewer shadows and lower power draw.

Low-cost LED strip is now readily available and seems to be good enough.  Add some aluminium extrusion, low-voltage wiring, power supply and simple dimmers and it’s time to experiment.

LED Modules

To make the system easy to manufacture, install and maintain, I decided to make manageable standard modules.  Using 25×3 mm extrusion, eighteen 1.6M lengths attached to the upper roof timber covers the entire garage.  The LED strip is the standard non-waterproof, 5630 x 300 12V.  2-pole JST connectors allow easy connect-disconnect.

Each module consists of two strips of 48 (96 total) 5630 LEDs wired in series for 24V operation.  A 1.6A 30V PTC self resetting fuse provides over-current protection in the event of a failure or short.  All connections are at the centre of the module.

At 24V each module draws about 1.7A, but at 20V it drops to 1.15A and the light output does not reduce by much.  So running at about 10 watts per module is produces less heat, almost as much light and the LEDs should last longer.

Failures – Warnings

There are two main problems with this low cost Chinese LED strip, both relating to the sticky tape on the back.

  1. it does not reliably stick to most surfaces, even clean smooth aluminium.
  2. it is not an effective insulator when stuck to a conductive surface – aluminium.

LED termination with fuseThe sticky backing does not reliably stick to hold the strip in place.  Especially when the strip has been in stock unused for a while.

I found that when the LED strip was attached directly to aluminium extrusion, short circuits between the exposed traces on the back of  the strip and the extrusion were not uncommon.  Two opposing shorts on one module and the LED was shorted.  The extrusion could also be live, connected to +ve or -ve of the main supply.  With two strips series connected,  a short on one  strip could applied 24V to the other 12V strip – causing LED failure and serious overheating.  The sticky backing on the LED strip can not be trusted as an insulator.

Another issue was the dodgy manufacturers soldering connecting LED segment on the reel.  This must be checked and tested and improved where necessary.

A Hot Garage Roof – another story

While installing the lights I noticed that the roof space is very hot.  It’s summer now and the roof is painted a red-brown and attracts a lot of heat.  So I did experiment with an extractor fan to vent the roof space.

With a darkish redwood colour on the roof and summer sun, even a reasonably substantial extractor fan can only drop the inside temperature by 2-3 deg-C – 41 down to 38 on a not-so-hot day.