Category Archives: Electrical Fascination

New Toy: Chumby!! (open source hardware!)

I get to play with a Chumby!  Chumby is an open source hardware “Window to the Internet”, or ambient information display, meaning it scrolls through a variety of information sources and presents the data for you to check out at a glance.  It does wi-fi, audio, photos, and videos, and has a touchscreen and an accelerometer.  I met Open Source Hardware superstars Bunnie Huang and Steve Tomlin at Foo Camp, and am getting to try one out via them.   Yesterday, it arrived in the mail, and I’m psyched make stuff on it!

 

chumby

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Electronics Update: My New Workbench

I’ve finally arrived in Cambridge: I built myself a work bench to do electronics on. That means I’ve finally arrived here!

I think it’s pretty sweet. Here are Star’s essentials:

star's new electronics workbench!

Stuff on the desk: my awesome weller soldering iron (I missed you while I was gone!), the world’s smallest/cutest single channel scope, AVR programmer, board etching stuff & copper clad FR4, toaster oven, The Art of Electronics, a couple of projects I’m working on: an OLPC that I need to make boot, a Meggy Jr to play with & program, some experiments with DIY plastic forming, and some various stuff on breadboards!

I’m looking for new Weller tips if anyone has any == I have an EC1002.  Also, feel free to come over and play!

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The Coolest Open Source Hardware Projects In The Land

The coolest open source hardware project I’ve seen to date is the TuxPhone + Open Cell Phone Project.

The Tux Phone is a GSM cell phone you can build from parts, originally developed by Surj Patel. Apparently he got into a Hulk-like Rage one day in 2005 and, fed up with the state of available cell phones, decided to make an open source hardware cell phone! It’s not sexy or tiny, but you can build it yourself.  And that means that if it doesn’t do what you want, you get to make it better!

The Open Cell Phone project is the other half of the project, and provides a Free operating system.  I’m not sure if the TuxPhone project is still alive today, unfortunately, but I think it’s pretty awesome!

I also just found out about the Open Cores and Open Graphics (as in graphics cards and drivers) projects, which are both way cool as well.

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Hack Tragedy!

In classic pre-deadline efficiency, I’ve spent the last two days finishing EVERYTHING before I travel home and can’t work on this stuff anymore. This push culminated, tonight, in my determined wiring up of the motor controller for what would be my electric Roman Chariot.  For now, it’s still just the electric roman chariot Project, and after tonight, it’s even further from getting done.

After two hours of careful soldering with the World’s Most Broken soldering iron, and only a few inches of solder to work with, I had it finished, everything connected as it ought to, and with that gleaming spark in my eye, I plugged in the last few connections and lightly brushed the +36V cable against the contact.  Now a real spark could be seen in my eye, reflected for a split second from the battery terminal.  I mean the batteries sparked, a whole lot at that brief connection, way more spark than I expected.  That meant a lot more current was flowing than I expected, and should have been a warning signal to me that my circuit was off.  

But after two days of COMPLETION I forged boldly forward because I had to see if the throttle worked.  This time I plugged the motor in fully, and twisted the throttle, and.. the motor didn’t change speed at all, but the throttle, in my hand, started smoking.  Not just a little, a whole hell of a lot.

I took several moments to observe my throttle, still smoking, in silence.  When something dies so spectacularly, it’s clear: there’s no going back.  My throttle is toast.

 I will have to wait a whole week until I get back and until I can find another throttle for this scooter, to make any more progress on this.  eit!!

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Electronic Scooter Hacking

I’m learning.  I’m converting an electric scooter I found to a horseless electric roman chariot, for personal transportation, of course, and I’m making the motor controller work today.

I was lead to believe that I could treat my scooter throttle like a big resistor, a big potentiometer.  TURNS OUT that mostly they’re hall effect sensors that give you a varying voltage (0-5V in, 1-4 out).  I didn’t find a lot of info on this on the internet, but thankfully Geo filled me in on some of the details, and I used my power supply and voltmeter to figure out the rest.

So, my circuit is getting modified (in the direction of simplicity, awesome) and will not involve a 555 to PWM the motors to the tune of a throttle’s varying resistance.  I think maybe this is helpful information to publish! More Roman Charioteering to come!

 

I also found this website informative: http://www.ebikes.ca/troubleshooting.shtml

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Today in Magnetism

Oh physicists, you’re always injecting so much personality into the way we think about the world.  Today brought the discovery that when a physicist talks about reluctance, they mean the magnetic version of electrical resistance.  A magnetic resistor, so to speak.

So, something with high reluctance blocks the flow of magnetic flux, and causes a ‘magneto-motive force drop’ across the region.  The whole construction lets you pretend that magnetic fields and magnetism act just like electric fields and so you can use electronics laws to figure out whacky things like “magnetic circuits”. 

I’m still getting a handle on the differences between magnetic “permeance”, “permitivity”, and “permeability” (and I’m grateful for any insight) — on the other hand, I now know that “coercivity” (imagine that) is the ease with which a material can be demagnetized.  Neodymium magnets have an especially high coercivity — it’s hard to [coerce them to] demagnetize.

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Magnetic Circuits and Permeability

New levels of understanding!  From the well-recommended text, “Electric Machinery”:

A magnetic circuit consists of a structure composed for the most part of high-permeability magnetic material. The presence of high-permeability material tends to cause magnetic flux to be confined to the paths defined by the structure, much as currents are confined to the conductors of an electric circuit.

So I can finally think of permeability in a clear way:  as an analogy for conductance, like copper conducts current, a high permeability allows for “conductance” of magnetic fields.  Way cool!

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