DIY 12 Volt LED light strip bar

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).

My home made 12 V LED light bar in action with two LED strips, about 540 Lumens.

My home made 12 V LED light bar in action with two LED strips, about 540 Lumens.

I bought a 5 m white LED (WLED) strip light roll and some switches on ebay. Here are the specifications for the strip:

LED 5630 SMD
Colour temp. (K) 5000–5500
Viewing angle (deg.) 120
LED density (LEDs/m) 60
Intensity (lumens/m) 840–900
Current (A/m) 1
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:

AWG 2 A 4 A 8 A 16 A Current
1 m 22 22 18 16
2 m 22 18 16 12
5 m 18 14 12 8
10 m 14 12 8 6
15 m 12 10 6
20 m 12 8 6
Twin-core
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:

ISO 2 A 4 A 8 A 16 A Current
1 m 0.5 0.5 1 1.5
2 m 0.5 1 1.5 4
5 m 1 2.5 4 10
10 m 2.5 4 10 16
15 m 4 6 16
20 m 4 10 16
Twin-core
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:

  1. The maximum current rating of LED strips is low (typically 5 A) and maximum strip length is short (typically 5 m).
  2. 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.

Detail of home made LED light bar with wiring cover removed. This end is thicker to accommodate the diameter of the switch.The plastic cover has a foam gasket. The wiring cover has a rubber gasket (recycled bicyle tube, contact-glued on). I contact-glued aluminium foil inside the fixture to minimise reflection losses.

Detail of home made LED light bar with wiring cover removed. This end is thicker to accommodate the diameter of the switch.The plastic cover has a foam gasket. The wiring cover has a rubber gasket (recycled bicycle tube, contact-glued on). I contact-glued aluminium foil inside the fixture to minimise reflection losses.

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.

Wiring diagram for two parallel LED strip lights (only 3 LEDs shown in each strip). Switch 1 (master) controls both strips. The optional switch 2 (dimmer) controls the second strip. For electrical safety, there is an in-line fuse between the supply and switches (2A mini blade fuse in my case).

Wiring diagram for two parallel LED strip lights (only 3 LEDs shown in each strip). Switch 1 (master) controls both strips. The optional switch 2 (dimmer) controls the second strip. For electrical safety, there is an in-line fuse between the supply and switches (2A mini blade fuse in my case).

wiring2

Wiring diagram for two parallel, individually-switched LED strip lights (only 3 LEDs shown in each strip).

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.

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2 Responses to DIY 12 Volt LED light strip bar

  1. G sumo says:

    Consider centre feeding your strips or dual end feeding them. Works great! G

    • bulumakao says:

      I understand that “end-feeding” means to connect the positive and negative at opposite ends of the strip. This way the voltage doesn’t drop along the strip and all LEDs get the same voltage and shine with the same brightness. For long strips, end-feeding could result in a substantial increase in total light output.

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