UE Boom 3 dock (fixed cable)

prusaprinters

The Boom 3 from Logitech/Ultimate Ears uses a proprietary charging 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).As I got my first 3D printer (an Original Prusa MINI+) a week ago I decided to build my own compatible charging dock as a first project. A small comparison of the result:OriginalThis Versioncharging indication LEDno LEDmicro USB jack (cable not included)fixed cable*too big for the Boom 3 as this dock is designed to also charge the Megaboom 3perfect fit for the Boom 3only available in whiteevery color imaginableimproves the gain of Logitechimproves maker skillsno assembly needed~ 1 hour for the first assembly, ~ 10 minutes for all further builds once you figured everything out~ 20-40 €~ 3 €* an updated version with a USB-C connector can be found here Note that this version is designed for very specific components:1x USB Cable with a diameter of ≤3.9mm (as the hole is 4mm in diameter)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)2x 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 two crimp connectors are 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 chargingTools needed:Soldering ironGlue gunCrimping pliers (see image)MultimeterUSB power bank for testingSuperglue (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:Print the two parts (I recommend 20+% infill, you might want to use the adaptive layer height function of PrusaSlicer to get a smooth finish on the nipple on the top part)Check that the spring contacts fit in the three holes in the top pieceCheck that the top piece can sit flush on the bottom piece without the spring contacts in placeCheck that the top piece can sit flush on the bottom piece with the contacts in place and be sure that the contacts stick out to the full extent of the “springy” partCut the USB cable to the desired length + ~8 cm and put it all the way through the hole of the bottom part (until the USB connector touches the bottom part from the outside, this will make assembly easier later)Strip ~ 8 cm of the outer protective plastic cover of the USB cableStrip ~ 3 cm of insulation of the plus and minus cables (red and black cable; you can cut the other cables, if any, as no data transmission will take place; see image for reference of 5-7)Add the heat shrink over the cables to protect the connectors from shorting laterTricky: The connector for the middle spring contact has to be bend twice to fit into the hole and still make contact to the middle spring contact. See the close-up image for reference.Crimp the two connectors on to the plus and minus cableSolder the spring contacts to the connectors (see picture).Using the multimeter double check that now both spring contacts connect to only one of the plus and minus terminal of the USB plug.Stick the three spring contacts with the soldered connectors into the top part: The spring contact connected to the minus terminal should be in either one of the outer holes, the spring contact connected to the plus terminal should be in the middle hole. Be sure that the two connectors do not touch (pull the heat shrink added in step 8 over them)!First test preparation: Turn your speaker on. Connect to it using Bluetooth and open the official Boom App. On the home screen, the battery percentage should be visible. Charge your speaker the ordinary way via micro USB cable using the power bank you will use in the next step for testing as a power source and wait for the icon next to the battery percentage to change to a lightning symbol (this takes up to 30 seconds, you can force a status update by entering and leaving the settings tab of the app; gear symbol in the top right corner).First test: Disconnect the charging cable. Be sure the App now does not display the lightning symbol anymore. Check your wiring once again (12.) as this is the step where you can destroy your speaker and/or power bank if any errors occurred in the process. Turn your speaker upside down. Push the top plate upside down onto the bottom of the speaker so that the two outer spring contacts touch the outer metal part of the speaker's connector and the middle contact reaches all the way down the middle of the speaker's connector. Be sure your crimped connectors still do not touch (see step 13). Do not touch any contacts/metal, only the plastic of the speaker and the top plate. While holding the top plate with the spring contacts firmly in place connect the USB connector of the cable to the USB power bank used in step 14. Force the Boom App to update the charging status by entering and leaving the settings menu (see step 14). If it does charge now: Congratulations, you are nearly there! You may unplug the cable from the power bank and proceed.If the box does not charge: Repeat step 14 to verify that the speaker and power bank are still working. Repeat step 12 to verify that the connections are solid.Move the USB cable so that ~ 2-4cm of the cable with all its protective layers are inside the bottom part. Use hot glue on this area of the cable to fix the cable to the bottom. Be sure that no hot glue sticks out above the inner rim of the bottom part as the top part will not sit flush otherwise.Tricky: Put the two halves together without glue and test everything again (see steps 14, 15). Be sure that the cables are neither squished nor pulled. When everything works, fix the connectors to the top part using your glue gun.Put the two halves together using super glue on the rim of the bottom. Wait for the super glue to dry according to its instructions. Congratulations, you are done! As this is my first post here any feedback is appreciated. Happy printing from Munich, Germany!