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.
“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.
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!
Recently Roy and I set out to build set out to build a better headphone amplifier for our higher end Sennheiser headphones. A headphone amp simply boosts the power to the headphones a bit, this results in better sound on the bigger headphones. The design is built around a know design over at Diy Audio Projects. It is a Class A amplifier with a 12AU7 tube. We ended up puting a spin on the project and added a PCM2704 USB DAC (sound card). Sweet glowing tube action pictures are below.
A friend of the group, Brandon Tice, will be coming back to teach another Cisco Networking Class. This class will build on the information learned in the first Cisco class but will still be easy enough to follow for entry level network skill. This will be a hands on demo where you will need to bring your own laptop. We will be providing a USB/Serial adapter for you to connect to a set of Cisco equipment and configure. You’ll be working with the Cisco IOS software to setup and configure your set of hardware in varying configurations. We’ll be doing small class sizes with multiple classes.
Class size is limited to 5 people. The class is going to last approximately 1 hour. Each of the 3 classes will cover the same content.
Where: The Space
When: Feb 18th Noon to 1:30 PM, 2:00 PM to 3:30 PM, and 4:00 PM to 5:30 PM (click link to book your seat)
Cost: $10 for Members $20 for Non Members
What you Need to bring: Laptop w/ at least 1 free USB port (We’ll provide USB/Serial Adapter and Cisco Hardware)
Space is limited. Please confirm your booking and pay via Paypal at your earliest convenience. All bookings are first come, first serve.
Direct Links to Each Event: (you don’t need an account to book your spot)
Noon to 1:30 PM: http://www.midsouthmakers.org/
2:00 PM to 3:30 PM: http://www.midsouthmakers.org/
4:00 to 5:30 PM: http://www.midsouthmakers.org/
To cancel or check the status of your booking: http://www.midsouthmakers.org/events/my-bookings/
Today a buddy at work got a new PowerBag, come to find out the micro usb cable would not charge his Galaxy Nexus. The .8 A that the micro USB port was putting out was not enough to charge the device. Luckily there was an apple port that was rated to charge devices at 1 amp. Since he doesn’t own any apple devices, a quick snip took care of the Apple plug. A little solder, and a donor micro USB cable the PowerBag had a brand new micro USB that would charge the Nexus!
We discussed briefly whether we would have a 4th Wednesday meeting in December (We WILL NOT have a 4th Wednesday meeting in November). As the 4th Wednesday falls in the holiday doldrums on December 28th it might be fine for an informal, project show and dream and tell meetup. Roy will be there no matter what.
Rick showed the programmable LED artwork he made with pool concrete, LEDs and film canisters.
Roy showed the LED t-shirt he screenprinted (his first) and lit with the knowledge he got from Rick’s LED class. Roy also showed my first steps with Arduino — a PWM sketch that faded in, then faded out an LED. Woo hoo!
Dru demonstrated us his excellent progress on the sewing machine that Judith had brought. After removing the rust on a few key components he had it cranking and sounding like a real live stitching machine.