We’ll be holding a second hackathon 2:00pm-9:00pm Saturday February 6th. A couple projects we’ll be working on are our big near space balloon event and some beer brewing and bottling. As always bring your projects, bring your Arduinos, and bring your excitement!

We’ll be holding it at Jay’s house again, if you’re interested in attending and did not come last time, please contact info@workshop88.com for the address.

Let us know if you’re coming and discuss potential projects on the forum post.

You DO NOT have to be a member to participate in the project or come to the Hack-a-thon. So please, tell your friends! The cost of the parts for each power supply ($11) you’d like to convert will be due to our treasurer at our next public meeting 01/04/2010. You are responsible for bringing your own power supply to the Hack-A-Thon to convert.

And as mentioned at the meeting if you want to bring another project to work on that’s great, just keep in mind Jay graciously volunteered his house, so let’s keep it reasonable. Those interested in attending will be given an address and directions at our next meeting (or upon request if you cannot make it).

Please stop by the forum thread for more details and let us know if you’ll be attending.

I own an old Braun Oral B electric toothbrush.  It was a gift, and I consider it a luxury I wouldn’t own otherwise, but I have grown accustomed to it.  Recently it’s decided to show it’s age by slowly charging less and less.  So, like any good maker who doesn’t like buy new things, I found the seal at the bottom and cracked it open.

Inside it’s pretty much just an on /off switch, the battery, which takes up the bulk of the internals, and a small charging circuit, which is the circuit board you see. Connected to the board at the very bottom is the induction coil, it’s used for the toothbrush’s contact less charging system.

It looked like the upper seal had failed and allowed water to seep in, there were small bits of corrosion on the motor and on the spring keeping the battery and coil in place at the bottom. First thing I did was check to see if the induction coil was still working by popping it on the charger and seeing if I started to get a decent current from it. And turns out, that’s where my problem was. Either the induction charger for the toothbrush, or the charging circuit itself were bad. Since the induction charger really needs to maintain it’s factory watertight seal to remain safe (it runs on household 110v), I decided not to venture into it. But I was interested in the coil and battery, and decided to have a look.

The coil, as you can see, is pretty tightly wound. So tight, in fact, that the photo I took makes it look almost like a solid metal ring. The entire thing is made from a very very thin wire you see sticking up in the photo, that wire is one of two leads that connect to the charging circuit.

The battery is actually made up of two individual cells. The cells are tied in series, and wrapped together, which is a pretty common practice.

Speaking of common, both cells were in fact a pretty standard 1.2v Ni-Cad cells. Which I just so happen to have on hand…

Well, not quite the same form factor, but readily available, and the exact same voltage. I just slapped them into a battery enclosure I had lying around, and voila, a working electric toothbrush. I left the old battery out and routed the wires through a freshly drilled hole in the bottom. It’s a little bit a of a kludge, but It works!

As part of our first public meeting this Monday, we handed out a bunch of :CueCats to everyone who attended, along with a challenge: tinker with them, see if you can get them to do something fun, and share it with everybody at the next meeting.

I’m planning on using mine to build a handheld barcode scanner based on an Arduino and the touch screen from a Nintendo DS that stopped working a while back.  It may be a bit ambitious, so I’ll probably need help along the way.  I thought it might be helpful for others to see what I’m doing in case they get stuck in their own projects.  The Arduino is in the mail, but while I wait on that, here’s the progress so far.

The devices we passed out were model #68-1965-A, rev. 06A00.  These are all PS/2 models, so there’s a bit more of a challenge involved if you don’t have a computer with a PS/2 port and a non-USB keyboard.

Upon removing the case (4 small Phillips screws in the base and 4 even smaller ones on the PCB), I discovered that these must have been late-model 06A00′s, since rather than the chip shown in most pictures online, there was a blob of epoxy more commonly seen on the 07A00 series devices.

The back of the board has a connector for the PS/2 plug, but unfortunately it isn’t removable, so for the moment, I left it alone. The variable resistor apparently adjusts the scanning speed, but I haven’t tried changing the setting yet.

After a bit of searching online, I found that even thought the IC in the center of the board may have changed, most of the other circuitry was the same as the old model, so disabling the serial number for this device was as simple as cutting a single trace so that one of the pins of the IC just below the U6 label on the board floats.  I just used a utility knife, it doesn’t really take much.

This is the output from the scanner, both before and after cutting the trace above.  I ran it through a simple perl decoder script because I haven’t wired up the device to do the decoding yet.  As you can see, after cutting the trace the serial number no longer appears in the output.

The next step for me is to get the device to decode the barcode string before it outputs it to the PS/2 line.  cexx.org indicates that by this can be accomplished by tying R6 high from any of the +5V lines on the board, so I’ll give that a shot.  (Thanks to Kevin R for pointing that out!)

Hopefully my Arduino will arrived in the next few days and I can start moving forward with the next stage of the project!