Deck Post Cap LED Lights

Introduction: Deck Post Cap LED Lights

About: Retired Quality Engineering Professional

I replaced our wooden deck with composite decking and PVC rails. I was please with the finished product, but I really wanted to add some lighting to the deck. Looking online I found many solar powered lights to the fit the 4"X4" posts. I really did not want to use solar since the life expectancy is rather short. Low voltage lights were available, but outside of my budget. I decided to try my hand at a DIY light using the existing PVC caps and LEDs. I am using 18,5VDC power supply (I already had one) so you will need to recalculate the dropping resistors for the series LED strings we will be building if the voltage is diffrent. The LEDs I used have the following specs:

  1. Diameter: 5mm
  2. Emitted color: White
  3. Reverse voltage: 5V
  4. Forward current: 20mA
  5. Peak current: 100mA
  6. Power consumption: 120mW
  7. Angle: 45 degree
  8. Forward voltag: 3.0-3.2V
  9. Backward current: Max. 20mA
  10. Luminous intensity: 15000mcd

You can use the following web-site to calculate your resistor needs:


Each cap without the path light options used 10 LEDs and 2 resistors and 1 piece if 1-1/2" X 3/4" PVC pipe.

If you add the path lights you will need an additional 5 LEDs and 1 resistor.

1 post cap is required along with some aluminum foil and hot glue.

Step 1: Light Ring

Cut a 1-1/2" PVC pipe to 3/4" Length. 1-1/2" is about as small as you will want to use as it can cause problems getting the LEDs installed in the next step. Larger sizes should be OK as long as they don't fill-up to much of the post cap interior.

Step 2: Drilling the Light Ring

Mark and drill 5mm holes in the light ring. The circumference of the 1-1/2" PVC is about 6". Mark 5 locations on the "top" of the ring, and 5 at the "bottom" of the ring. The will be about 1-1/4" between the marks. Absolute precision is not required! Just make it even by eye!

Step 3: Installing LEDs in the Light Ring

The LEDs will have a long lead (positive) and a short lead (negative). I find it helpful to put a black mark on the short lead prior to loading the light ring. Put the LEDs in the ring with the black mark pointing in the same direction to facilitate the connections. Solder the positive lead on the first LED to the negative lead on the next LED making a series connection. Continue until the last connection, leave the positive lead on the "last" LED and the negative lead on the "first" un-soldered. These will be the connects to the dropping resistor (negative lead) and the positive supply lead, Turn the light ring over and repeat the process. It is easier to install and solder one side at a time as the leads form the structure to hold the LEDs in the ring. Solder the open positive leads for each side together to form the connection to attach the positive voltage wiring. Bend each of the negative leads to on side of the ring. See picture 3 above. Solder a resistor to each of the negative leads. Twist the open leads on the resistors together to form the connection for the negative voltage lead wire. Solder a Red lead wire to the positive leads that were soldered earlier. Solder a black wire to the common leads on the resistors. Apply your designed voltage to the ring to test the operation. Most common problem will be an LED installed in reverse, power supply voltage plus and minus not properly identified, open solder joint between LEDs.

After testing, hot glue resistors and wires to the inside of the ring to act as a strain relief for the wiring.

Step 4: Preparing the Post Cap (no Path Lighting)

The post caps I used are described in the first photo. I made a quick templet to use for marking the holes that will be drilled in the caps for the light to shine through. I used a 5mm drill bit for all holes as this is the size of the LED cap. This facilitated adding the path lighting if desired. Drill all 20 holes.

Step 5: Adding Path Lighting to Caps

If you want more light than the light ring provides, you can add more LEDs that are exposed through the caps. I used the same template to hold the LEDs for soldering as was used to make the location of the holes in the cap. Press the LEDs in to the holes you have drilled in the template and bend the leads on the LEDs at 90 degrees close to the body of the LED. Again assure you are connection plus to minus on the LEDs. The lead act as the "structure" to hold the LEDs in position, so make sure as much of the leads overlap as possible. Add the resistor to the open negative lead at the end of the string. Solder the black wire to the resistor, Solder the red wire to the open positive lead a the other end. The caps I used have a molded corner brace that needed modified to allow the path lights to be installed. Final image shows the LED string installed into the cap, Hot glue the leads on the LEDs and the wires to provide strain relief. Be carful to not short any of the leads.

Step 6:

I used aluminum foil to make a reflective surface in the cap and to avoid the lights showing through the top of the caps. Hot glue the foil in the corners and make 4 small holes in the foil in a spot that will intersect the light ring when installed. This provide a more stable mount for the light ring. Connect the light ring and the path light (if installed) to the power supply. Run the wires inside the PVC post cover and connect to your outdoor rated power supply. I also built a dusk to dawn circuit to turn the lights on and off. Just search the web for a TRIAC dusk to dawn schematic.

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    Elaina M
    Elaina M

    2 years ago

    This turned out awesome ! Way to be resourceful and thanks for sharing !!