UE Boom 3 dock (USB-C socket)

The Boom 3 from Logitech/Ultimate Ears uses a charging docking mechanism on the bottom. A dock from Logitech/Ultimate Ears is available. It contains one LED (to show the charging status) and a micro USB connector. The “magic” behind the charger is that it simply connects the minus terminal of the USB cable to the two outer spring contact and the plus cable is connected to the middle spring contact. Some simple logic is added for the charging LED. With a recommended retail price of 39,99 € (available on amazon.de for about 20 €) it is heavily overpriced (the word rip-off comes to mind).

This is an update of my original post. A comparison to the original version by Logitech/Ultimate Ears:

* the first version I designed used a fixed USB cable and can be found here.

Note that this version is designed for very specific components:

• 1x USB-C female jack with a length of approx 14.5 mm (the ones I got: https://de.aliexpress.com/item/1005001900635444.html)
• 3x Spring contacts with dimensions in the image (the set of 100 I got:  https://www.amazon.de/gp/product/B07WP196KW; however the dimensions in the amazon listing are imprecise)
• 1x Crimp connectors with a hole that fits the “springy” part of the spring contacts and a width of 2.8 mm on the front part (the set I used, also see pictures: https://www.amazon.de/gp/product/B07VFGVLZC )
  Only one crimp connector is necessary, you could however also connect the other outer spring contact to the minus terminal of the USB connector. Either way, all three spring contacts should be utilized to facilitate a planar base for the speaker while charging
• 2 short wires
• optional: rubber feet sticker

Tools needed:

• Soldering iron
• Glue gun
• Crimping pliers (see image)
• Multimeter
• Superglue (or any other glue you use for PLA components)

Warning: 

• Please keep in mind that any errors (esp. re. the wiring) could result in you destroying your speaker and/or power bank (and/or an electrical short and potentially fire later). I highly recommend using a power bank as a power source for testing the dock instead of a charger plugged into mains voltage.

Detailed assembly instructions:

1. Print the two parts. I recommend using the ironing feature of PrusaSlicer for the top surface of the top part. You can also decrease the layer height for the nipple on the top part. The top part needs supports in the middle but only for the first 6.9 mm and also under the USB-C connector. The base does not need supports.
2. Clean the parts and check that the spring contacts fit in the three holes in the top piece.
3. Tricky: Insert the USB-C female jack into the hole from the inside. Make sure that the pins for VCC and GND are facing you. This might need several attempts as the fit is very tight. This tight fit is needed to secure the connector in place.
4. Tricky: Bend the crimp connector for the middle spring contact twice to fit into the hole and still make contact with the middle spring contact. See the close-up image for reference.
5. Crimp the connector to the cable designated for the middle pin.
6. Put the base of middle spring contact through the hole of the bent crimp connector. Solder the two parts together. Avoid solder getting any lower than the bottom of the spring contact.
7. Solder the second cable to one of the remaining two spring contacts.
8. Insert the spring contacts with the bent crimp connector in the middle hole of the top part. Insert the other two spring contacts to the outer holes.
9. Carefully solder VCC to the cable going to the middle spring contact. Also, solder GND to the cable going to the other connected spring contact. Make sure the cables move away to the sides of the connector (as the base contains a bump that will otherwise crush the cables, see the close-up picture for reference).
10. Check the connections using a multimeter. You can use the Ultimate Ears App to confirm that the speaker is charging. See steps 14 and 15 in my original post for details.
11. Use hot-glue to fix the cables and connections in place and to isolate the cables and connectors from one another.
12. Check that the base part still fits. While the top part is facing down, add super glue to it's inner rim and glue the base part in place.
13. Optional: Add rubber feet stickers.
     

Any feedback is appreciated. 

Happy printing from Munich, Germany!