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HTC Sensation Inductive Charging – Another Lunchtime Hack

by on Sep.06, 2012, under Electronics, Projects

Ever since the Palm Pre came out I’ve been in love with it’s inductive charging upgrade. Similarly to the Powermats, the charging base acts as a device stand with it’s integrated magnets in addition to charging your device without having to plug and unplug your device every time you need to use it. Once on the charger it outputs 5.50v. It’s a bit higher than other USB chargers I’ve used.

touchstone charger with back

Inductive charging back with base

“Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in proximity combine to form an electrical transformer.” -Wikipedia


After peeling off part of the backing you can see the coil and it’s output circuitry. You can also see the four magnets it uses to attach itself to the charging base. They do a good job of holding my heavy phone and case to the base.


After finally getting in the Touchstone base and replacement back I decided to get this working over some lunch. I was a bit uncertain at the time that the magnets would be able to hold my phone while it’s in it’s case. I also wanted to make sure that I wouldn’t experience any signal loss issues or suffer from any overheating while charging. I found the quickest way to make this work was to take the male end of a microUSB plug and wire it directly into the contacts off the inductive back. After taking apart the microUSB plug from a spare dead cable, you can use a 200 ohm resistor to short the D+ and D- pins on the plug. This allows the device to charge at a higher current, which will in turn charge a bit faster. After soldering it up I used some colored silicone to insulate the back of the plug.

Roughed in and adjusted the case to improve clearance


It works!


In order to clean this up and make it a bit more permanent and presentable, I have get away from using the charge port and get it through the housing. Unfortunately, the back housing of my phone has a nice metal frame right where I want to mount it. There are also a few antennas I need to avoid. The induction coil is going to have to stay on the back of the case, and somehow get passed thorough the metal housing into the board. I drilled through the back of the case near the sim card holder.

It took a bit of poking and prodding but I was able to find 2 test points that when the motherboard was plugged into a USB charger had +5v showing between the points and the ground plane. No magic smoke was released!


After a bit of soldering I was able to route the positive lead out of the phone housing and is now staged for the next step- going through the housing and into the case. The metal frame of the sim card holder is attached to the ground, so I can use that to complete the circuit. On a normal USB type charge port the ground pin attaches to the ground plane which is usually where all the shields are anchored into so I feel safe doing the same.


For the next stage of the project I’ll have to use some contacts or pogo plugs embedded within some silicone to go from the inside of the phone to the contact points on the induction charger. Ben had the good idea of using some thin copper PCB protoboard to act as thin traces.

To be continued!

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Adventures in Rapid Prototyping: Shaving Brush Stand

by on Apr.17, 2012, under Projects, Prusa

I have a badger-hair shaving brush that I’d like to keep for a while. I’ve read that the brush will last longer if it’s allowed to hang and dry versus being left sitting in the lather bowl. After looking around for a hanging stand I decided to make my own. My first model took over 6 hours to print at 60mm/sec.

Version 1 of my Badger-hair shaving brush stand

 It turns out I made the model quite a bit larger than necessary. After placing the brush and the razor on the stand, all the extra unused space is really evident.

Brush Stand V1 In Use

I decided to see how much time and material I could save on my next model so I tried to use circles and ellipses to minimize the printed area while still leaving enough structure. The new model has a hanger for the razor and a slot with drain holes for the extra razor blades.

Shaving Stand Version 2

This model printed much faster, it only took around two and a half hours at 60mm/sec.

Brush Stand V2

The stand works well enough, but I’m not happy with how tall and light it is, it’s too easy to knock over early in the morning.

Brush Stand V2 In Use

For the next iteration, I’m going to flare out the base a bit to prevent tipping and may increase the amount of material towards the bottom of the model. The blade storage slot needs to be deeper as well.

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Adventures in Rapid Prototyping: Banner Stand

by on Apr.17, 2012, under Projects, Prusa

We have a banner stand that is starting to fail at work. The plastic collar is starting to crack. Rather than simply replacing the whole stand, I figured I could make a quick replacement clamp. 10 minutes later thanks to TinkerCAD we have our replacement part model.

3D model for the replacement clamp

Once the stand was disassembled, I  switched out and replaced the collar. It’s a bit brighter than the stock part, but the stand is repaired!

Replacement rod clamp for collapsible banner stand

Once I saw how easy it was to create models in TinkerCad, I decided to get caught up with some of our other needs. This is a replacement clip for a hanging banner.

TinkerCad render of the replacement banner clip model

The original clip slides into a channel, the replacement slid right in!

Replacement clip for a hanging banner

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A Very Maker 3D Valentines Day

by on Feb.13, 2012, under Projects, Prusa

I’ve been wanting to print some of the geared items on Thingiverse for a while. With Valentines day coming up it seemed like an excellent opportunity to try out the Screwless Heart Gears by Thingiverse user Emmett. After reading the assembly instructions the heart came together quite nicely with the help of a hot air gun to help let the printed pins slide in easily.

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