Custom DAI connectors

Experimenting with making my own durable connectors while re-using DAI pins from failed cables (2014-)

Similar projects worth following
This is a followup to my bluetooth headphones hack project.

The headphones are super reliable. The point of failure has been the custom length wires with DAI connectors. Inevitably the connection to the DAI pins fatigues and I have to remake connectors. To improve on this, I opted to make permanent DAI pin connectors, and attach new wires to these connectors, greatly simplifying the repair/replacement process.

My simple game plan would be to:

1) Use a mill to drill the holes in a piece of aluminum (actually probably into the edge of a 1/8" thick piece of aluminum)
2) Create an easy to disassemble "mold from more 1/8" aluminum
3) Fabricate pins with a lathe
4) Solder resistor/wire/pins (and put the heat shrink on in prep for the last step)
5) Put said parts into the mold
6) fill with epoxy.
7) Heatshrink

But there is a key improvement to make to this. The issue I've had for a while is that the epoxy-wire interface fatigues over time and necessitates replacement. Getting the DAI pins out of epoxy is not very easy.

So instead:

1) Create mold similar to above
2) wire the pins to a resistor and 2-pin connector (I have these; some tiny JST connector but I don't recall the part number)
3) Fill with epoxy

This would be a permanent (as in never have to remake it) connector to the hearing aids.

4) Hook up the male end of the JST connector to the wire going to the 3.5 mm jack. (solder, epoxy, etc; doesn't really need a mold)
5) Connect the two parts, hot glue them together, and shrink wrap.

So then when fatigue issues occur, remove the hot glue, and replace the wire portion. The wire and JST connectors are easy to buy!

The big question is what material to use for the pins. Brass is too soft (bends), unsurprisingly. Steel would need to be plated (ehh-effort).

Todo: investigate alternate copper alloys:

  • Overdue update

    Gertlex07/04/2015 at 06:35 0 comments

    I've now got a few of these connectors successfully made, and they work well. I never remade the mold; I continue to work with the one I have.

    The approach now is to use hot glue to hold the two mold halves together, put masking tape on one side, add epoxy. Then once the epoxy has set but is still slightly malleable, I pull the back half of the mold off, leaving the pins in the other half. I poke around, loosening the epoxy from the aluminum, and then let it harden fully before completely detaching from the mold. This preserves the spacing, while greatly easing removal of the pins. Grabbing the epoxy connector with vise grips in order to pull the snug pins from the mold works quite well, in fact.

    I never did further investigate making my own pins. I did just find some ~$35 DAI cables now being sold online, so I have a source of pins again... Ordered a pair just so I can assess the quality. (Answer: they're 2ft long, which is way too short for normal use, so they're going to be chopped up.)

  • Initial success

    Gertlex12/26/2014 at 18:09 0 comments

    I did a few weekends of work on this (summer 2014), which were successful and indicated ways to improve. Most importantly, I uploaded some pictures of this work!

    In particular, I made my mold smaller than necessary; it was tricky to remove the epoxied part. I also need to find a better epoxy that is both easy to mix in tiny amounts, and hardens well. I did not try using any mold release agents, though a coworker gave me some. I probably will try this in the future, but I suspect I'll get greater improvements by modifying my aluminum mold slightly (more tapers, for example).

    I am also thinking I will do an attempt with just hot glue. I suspect this will work, but due to softness, the tiny soldered connections will eventually break.

View all 2 project logs

Enjoy this project?



Similar Projects

Does this project spark your interest?

Become a member to follow this project and never miss any updates