12 Volt LED lights are expensive. 12 Volt LED light strips are cheap. I bought a light strip and made my own custom light bar for camping. The materials cost about AUD$20.
LED light bar design
This project upgrades my previous 12 V LED camping light. The objective was to install a rugged LED light bar in the back of my ute (pick-up).
I bought a 5 m white LED (WLED) strip light roll and some switches on ebay. Here are the specifications for the strip:
|Specifications for ebay 5630 LED strip light. The intensity is more realistically about 290–320 lm/m at this current.|
I wasn’t sure that one strip would be sufficient, so I installed two side-by-side. Some basic soldering skills are needed for attaching new leads after cutting the strip. I have actually found one strip = 290 Lumens/m × 0.93 m = 270 Lumens quite sufficent.
Small diameter power cables can be used when currents are small. For my design, 1 A/m × 0.93 m × 2 strips = 1.86 A. The following table can be used for sizing power cables:
|American Wire Gauge (AWG) cable sizes for 4% (0.48 V) voltage drop, twin-core cable. Read the cable size at the intersection of current along the top row and cable length on the left column. Calculated from American Wire Gauge data on Wikipedia.|
Here’s the same table with ISO (mm2) sizes:
|Metric (mm2) cable sizes for 4% (0.48 V) voltage drop, twin-core cable. Read the cable size at the intersection of current along the top row and cable length on the left column. Derived from the previous table.|
For bigger strip lights there are two important points to consider:
- The maximum current rating of LED strips is low (typically 5 A) and maximum strip length is short (typically 5 m).
- There could be substantial voltage losses along the strip.
The basic solution for the above problems is to use short LED strips in parallel.
LED light bar assembly
The strip lights I bought are waterproof. However, I wanted better protection from shifting cargo in the back of my vehicle. I made a lighting fixture out of thin timber strips (10 mm deep), with a plywood backing (3 mm) and a clear polycarbonate plastic cover (2 mm). The timber I cut myself from scrap and the plywood was leftover from other projects. Polycarbonate and acrylic (‘perspex’) can be found at a fibreglass supplies shop.
The two LED strips in my light are wired in parallel, for equal voltage and equal intensity. Here are two different wiring diagrams including switches.
The self-adhesive backing on the strip lights did not hold for long. I re-glued the strips with contact glue and secured the strips with four cable ties (zip ties).
The thin, flexible plastic cover did not seal well against the timber. I made a gasket from foam tape to improve dust and insect resistance.
According to my solar regulator, this light bar draws 0.7 A at 12.4 V with one strip (design 0.93 A) and 1.4 A at 12.3 V with two strips (design 1.86 A). The intensity is overrated in the first table above.