Introduction: 5 Dollar LED Lantern
I love our Coleman white gas lantern. It has been a reliable companion for many years. Never needing anything except an occasional mantel or pump rebuild to stay in tip-top shape. I do not like the heat it generates or the flammable fuel it needs to operate. I always worry that a poorly thrown football or a drunken wobble by Uncle Bubba will result in a nasty burn, or even worse, igniting a massive fire in our tinder dry forests. I stupidly made the comment that I could build a not-so-bright, but super safe lantern for 5 dollars. This was met by a chorus of laughter and the comment of "you can't even buy a McDonalds Big Mac meal for 5 bucks" Well that set the bar pretty low. The challenge was on.
Step 1: Parts
6 ea 1/2" SSS PVC T Home Depot 0.21 ea $1.26
3 ft 1/2" schedule 40 PVC Home Depot 0.20 ft $0.60
4 ea 38 mm beer pong/ ping pong balls Dollar Store $1.00
4 ea 8 mm 0.5 Watt straw hat LED ebay 0.30 ea $1.20
4 ea 1/4 Watt resistors (10 ohm for warm white LEDs. 22 ohm for blue-white LEDs) $0.25
4 ea 12 inch pieces of scrap twisted pair wire. (I salvaged mine from a discarded parallel printer cable) Free
1ea discarded USB cable. (Don't lie, I know you have a box full of these) Free
1 stick hot glue and a small amount of solder $0.50
For a grand total of $4.71
Step 2: Part Preparation
Cut the PVC pipe into three 1 foot sections. Cut up one section into four pieces 1/2" long and 3 pieces 1-1/4" long. If you wish to paint your lantern, now is the time to do it. Dry assemble the lantern pieces to form the basic final shape. Cut the leftover 1/2" PVC into 4 pieces and use as masking caps where the LED assemblies will be installed. You do not want any paint on the inside of the "T" pieces. Spray per can instructions and let dry.
I built a ball holder out of a scrap of 2X4 with a 1-3/8" hole drilled in it. Not required, but it will make your life easier. Drilling the LED hole in the ball is a little tricky. I found two ways that work fairly well. The best is to use a 5/16 brad point drill bit at a fairly high speed (3000rpm) This will make a clean hole and the drill waste can be removed with a small pair of needle nose pliers. A Unibit also works well, but the hole may need some trimming with an Xacto knife. You want the LED to fit snuggly in the hole. If it does not seal the hole completely, hot glue will seep in and ruin your lamp.
A third hand jig is very handy for the following steps. Solder your current limiting resistor to the LED Anode (positive connection) This will be the longer LED lead. Solder a 12 inch twisted pair wire to the LED / resistor assembly. Make a note of the color code for positive and negative connections. Inspect carefully for shorts.
We are going to use hot glue to encapsulate the lamp parts. This will provide an air tight seal for the ball which will help it maintain its shape if it is bumped. This also provides insulation for our connections and will act as a strain relief for our wire pigtail as well as mechanicaly connecting the mounting ring to the ball.
Insert the LED assembly into the hole in the ball. Make sure you have a tight fit. If you have any gaps, they can be filled with a gel type super glue. Slide a 1/2" piece of PVC pipe over the wires and rest it on the ball with the LED centered in the middle. Try to support the ball, LED, and wires so they maintain a centered alignment. Gently hold the 1/2" pipe mounting ring in place and fill the interior with hot glue. Continue to gently hold the pipe ring in place until the glue begins to set. Do not press down on the pipe ring. This will force air out of the ball and after the glue sets you will have a lamp with a flat spot.
I like to test the lamp assemblies at this point. If you have a bench supply with metering this is very easy. Set your supply to 5 Volts, connect the wires and verify the unit is drawing around 100mA. You can use any 5 Volt source and a DMM set to measure milliamps to do the same thing.
Step 3: Final Assembly
Drill a 1/4" hole where the two lower "T's" connect together. Make sure the 1-1/4" connector pipe is installed, you want to drill through it also.
Prep the USB cable by cutting off the non type A end and striping the outer sheath back about an 1-1/2" Carefully remove the shield braid and foil to expose the 4 internal wires. You should have red, black, green, and white conductors. Red is positive 5V and Black is negative 5V. Green and white are data connections and will not be used. Make sure the green and white connections do not short to themselves, other conductors, or the ground braid. I use aTy-Rap to hold the data wires out of the way and to provide a strain relief so the USB cable can not be pulled out of the lantern.
Layout all the pieces as shown. Thread the wiring through the "T" connectors. Strip all the wire ends and connect the positive wires to the red USB wire and negative wires to the black USB wire. Solder and insulate the connections.
Gently push the excess wire into the "T" connectors and assemble the pieces. You can use glue if you wish but it is not really needed. Do not press on the ball to seat the LED assembly. Use a scrap of wood like a popsicle stick to press down on the mounting ring while working from side to side to seat it. Install the legs and feet and you are done!
Step 4: Power Sources and Comments
You can power your lantern from many common power supplies. We tend to use the 5 Volt back up batteries that are popular for phone and tablet charging. Since the lantern only draws 400mA, even the smallest of these will run your lantern for 3 to 4 hours. A large pack (10000mA) can run multiple lanterns for 2 to 4 evenings before requiring a recharge. A laptop also works well, or you can build my LED Floodlight Power Station for a really long lasting solution.
Warm white vs. Cool white
For me, neither of these two are ideal. The warm is too green-yellow and the cool is too blue. I have tried building LED assemblies with one of each and the color is more pleasing to my eye but the fabrication is much more difficult. Also be aware that the forward voltage drop varies tremendously between the different color families, the warm white were almost 4 Volts while the cool white were around 3 Volts. This makes a huge difference in resistor selection with the warm white needing a 10 ohm resistor as compared to 22 ohms for the cool white. As far as usage goes, the cool white is better for task lighting and the warm for sitting around and shooting the breeze. Choose appropriately. One of each color is shown, with the tall lantern being the warm white and the short lantern being the cool.
This project was inspired by the PVC creations of George Blatchford(1930-2010) His PVC pipe palace awed and amused us. George was struck down by ALS (Lou Gehrig's disease) at far too young an age. Yet even in the grip of this terrible affliction, he never lost his sense of humor. I hope you find this instructable of use, and if so, please consider a small donation to the ALS Association.