Carbon Lantern Stick

For the traditional lantern parades on St. Martins day in Germany you need a stick and a light-source. Back in the days we used candles, but this often lead to drama when it caught fire. Today, you often get cheap plastic sticks with an LED for a few bucks. The problem with these is that they are so cheaply made that now the drama starts even before the parade. Either the metal from the switch or the battery holder is bent, unable to close the contact, or the wires of the LED are already ripped off. And if that wasn't enough, the AA batteries might die too soon. This was just way too frustrating, so I decided to end this one and for all.

The goal of this project is, thus, to make a robust, lightweight (the kids have to hold it for some time, long-lasting lantern stick.

• Varta Powerpack 2600 (amazon)
• 14cm Carbon Fiber Tube with 27mm outer diameter and 25mm inner diameter. (eBay)
• 40cm Carbon Fiber Tube with 10mm outer diameter and roughly 1.2mm wall thickness (eBay)
• 1 USB panel plug, series A, angled (reichelt)
• copper wire (no high currents, 0,14mm2 is sufficient).
• 1 JST Pin Header 2pins, 90° (reichelt)
• 6mm MDF board (if you want to Lasercut the slices).

I wanted to be able to exchange the attached light source, e.g., from a white to a red LED. I opted for the JST connector because it ensures correct polarity. However, a micro-USB socket would also be an option.

Tools

• Soldering equipment
• Saw
• Laser cutter or a 3D Printer

Make sure the tubes are well-attached without applying too much force, otherwise the tube might break. Use a sharp saw and cut at a right angle. I used a WorkMate to fix the tubes and the outer side of the table as a guide for the saw.

I cut the smaller tube to 40cm because I wanted to make two sticks out of the 80cm tube. I wouldn't go much longer as depending on the weight of the lantern, it can become quite hard for the kids to hold it over a longer period of time.

The role of these disks and spacers is to create a block that firmly holds the smaller tube in the bigger one, and hold the USB connector that will be pushed into the USB socket of the powerbank. The four small holes are there to loop the wires as a pull relief before running them through the smaller tube.

Cut a small opening for JST connector roughly 2cm from the end of the smaller tube. This will house the JST connector (see step below).

Start by soldering two pieces of wire to the JST connector. Isolate them using shrinking heat-shrink tubing. Insert the cables into the opening and fasten the connector inside the tube using a glue-gun.

Insert the smaller tube through the five topmost disks ans spacers. Loop the wires through the small holes and solder the ends to the outer two pins of the USB connector. If unsure, check the polarity using a multimeter by inserting the USB connector into the powerbank.

After soldering, add the last two disks and glue the stack together. Also glue the disks to the carbon tube. While this makes it more complicated to access the components in case of failure, but under realistic conditions, the tube will probably be pulled out of the disks.

Insert the pack into the larger carbon tube until the top ends align. The press-fit should be strong enough to hold everything in place without glue, but fixating it does no harm.

To connect the powerbank, insert it into the carbon tube until you feel a resistance. Now, turn it carefully until the usb-connectors align and you can push it to the end. Only the handle of the powerbank stays outside the tube to be able to remove it.

You can now attach a light-source of your liking to the JST connector which now provides 5V.

To attach the lantern, I used the hooks from the broken cheap sticks.

I didn't try this, but theoretically it should be possible to print the spacers instead of laser-cutting them. It's probably a little tricky because of shrinkage etc., but in case you wanna try it out, here's an STL-File you can start with.