DC Barrel Jack Magnetic Connection Modification


#1

I recently got a new laptop (Acer Switch Alpha 12) and it doesn’t have a magnetic connector like I would really love to have. I was thinking of adding one to it by getting a matching set of male and female connectors and adding a magnetic part to it. My idea was to keep a plug in the computer at all times and keeping the matching end on the charger at all times as well. So no permanent changes to either laptop or charger. I was wondering if anyone has done something similar and if you have thoughts on how best to do this.

Basically I’m looking for something like the old Macbook pro’s charger, but for DC barrel jacks. Sadly it’s only a 3.0 x 1.1mm jack (so quite small overall). I was looking at pogo/magnetic pins, but I want to see if someone has an idea in mind already.


#2

Just as an update to this (since I think I’ll use it as a pseudo build log), I’ve been looking into hacking a MagSafe 1 connector onto the computer. Not sure how I want to mount it, but it might make some things a little better. For one there are some features on the MagSafe charger which are attractive. The first one being a soft-start/low current check before providing full power. The second one would be the status LED, always nice to see when things are working. I’m still thinking that I’ll use the 3x1.1mm jacks and just attach either end of the MagSafe to the DC jacks.

There is a nice blog about the MagSafe connector and how it works here.

I found the internal connector on ebay, but here it is (for better pictures) on Aliexpress.

Few things that I’m not sure about though.

  • Does the MagSafe version matter for the output voltage? This has to do with the fact that the micro on the connector looks for a voltage drop before applying power.
  • The Switch Alpha 12 takes 19V @ 2.37A as an input (45W) and the MagSafes have a couple close contenders for the correct voltage range.
    • First one is the 18.5V (85W) and second is 20V (85W).
  • Does the Macbook do any communication with a microcontroller on the motherboard / or via the OS that isn’t on the small, little MagSafe board?
    • The connector uses a 1-wire protocol for the LED status, I might have to add in the smallest micro I can find to control the status if I want smart LED controls (as seen in the blog post).
    • I don’t see any chips on the internal connector, just that big black square on the top of the board. Have to say, I have no idea what it is. Looks like there is about 5 connections to it? Here is a great high quality image of the top. I think the identifier might be “L1”.
  • As I was writing this, I thought it might be a relay… But maybe not…
  • Last thing would be how to attach the board to the computer/DC jack with good strain relief. A 3D printed case would be nice, but still lacks a good semi-permanent mounting.

#3

Interesting. The magnetic stuff is definitely nice when a cord gets snagged, but I’m not sure I’d go quite this far. You will likely need to reverse engineer the 1 wire protocol (though maybe that’s part of the fun?).


#4

Yeah, I’m thinking I will get some of the parts and just play around with it. If it is too hard then I can rethink the idea. I could likely strip out the protection/1-wire if I pull the connector apart.

That being said, yes, that does seem hard. I’m still looking for other connectors too.


#5

Well you know you like the magnetic part, that’s good. The protections are there so there isn’t any sparking when you connect or disconnect the load (inductive load + quick disconnection = voltage spike / spark). So yeah, this could make for an interesting open source solution that others might enjoy. I have to say since switching to a macbook pro, I’ve lamented the USB C not having the quick disconnect option.


#6

Yeah, I’m thinking I will still try to make the MagSafe work. Do you think it matters which connection board I get? Since they have many different voltage/wattage ratings?

At least with the new Macs coming out there are magnetic USB-C cables being made. That is something that I could use to my advantage possibly, but I only have two ports on my computer. One USB-C and one USB 3.0. I’d rather keep my USB-C open for a dock at all times.