From the DIY drawer: Pogo pin module prototype
Back when I was looking at new phones, the Galaxy S II and Galaxy Nexus were the two identically priced devices that made it to the final selection. The Nexus has a bigger, higher resolution screen, NFC, pogo pin contacts on the side, and a higher version of Android from the factory. The S II only has a better version of AMOLED technology for its smaller, lower resolution screen, as well as a microSD slot. That microSD slot is why I now have a Galaxy S II, and every time I start to wonder if I should have bought the Nexus, I just have to look at the storage statistics for my 16GB S II with 32GB microSDHC card to see that I did indeed make the right choice.
I do wish I had some of the features from the Nexus though, and NFC and pogo pin support is higher on that list than the screen resolution. Aaron has shown us the potential of pogo pins, and the timing of that article fit rather well with my latest DIY project, a prototype pogo pin module.
The idea behind this module is based on my first tests with magnet based power. The magnets I used back then were too strong and interfered with the compass, and the fault of that design was that I wanted the phone to not just be magnetically attached to a holder, but actually be secure enough that the nightly fumbling of a contact lens-dependent me wouldn’t send it crashing to the floor. This new revision still incorporates a magnetic feature, but uses much smaller contact points, similar to pogo pin contact points, and still needs a dock to hold it.
The module itself consists of five magnets with wires going to them, soldered to a prototyping PCB and covered in Sugru. The idea is that should I ever decide to start using a module like this, I would simple merge it with one of those $1.30 cases of mine (and now Aaron’s) using more Sugru. This would allow me more flexibility with soldering both magnets and wires compared to making holes in the case that the magnets would have to fit through perfectly. The wires will have to go down underneath the case and out the bottom, into a microUSB connector and connected to the phone that way. This is basically the only way to make the connection to the phone, and the bulk it creates is why I haven’t gone ahead with it fully yet.
The reason why I’m using five contact point when USB has four and the Nexus has three pogo pin connectors is that microUSB actually has five. Four of those are used for normal USB, while the last one bridged to ground using various resistor values will trigger all sorts of things from USB host to car mode. Another reason to use smaller contact points is to allow for accessories to be created around the magnetic pogo pin connectors, and to do so I need that fifth connector. To elaborate, consider the system I created to automatically sync an MP3 player with my phone. If you could simply add the five pin magnet connector to an MP3 player and make it trigger USB host using pin four and five, you would essentially have an MP3 player you could magnetically attach to your phone using no additional wires, and have it automatically initiate sync when connected that way – without losing the normal USB functionality. Another use would be to make a flash drive that initiates host mode in order to transfer files, and a third would be a car or home dock that automatically initiates the appropriate mode when inserted in said dock.
While this is a working prototype that I could technically start making accessories for right now, I’m still on the edge regarding whether I should, and even if I do it will be another revision of the connector. This module is designed to go on the back, under the already lose rubber case I have. The problem with that is that the S2 is thicker at the bottom, even with an external battery as the case is made for the stock design, and creating a system that slides onto the connectors correctly while on the back is not easy, and would most likely require a system where you insert the phone like you do old music tapes. Ideally I would create a module that incorporates both the connector magnets and the microUSB connector in a single piece that inserts into the bottom of the device, but the problem with that is that the microphone is also on the bottom. A side-mounted system is not really an option due to the bulk it would add.
This whole magnetic connector thing is something I just can’t seem to leave be. On the one hand, it’s crazy to spend so much time designing and creating a system that doesn’t really save you much time or effort even in the long run. On the other hand, it would be incredibly fun to get this working.
