Tuesday, May 28, 2013

Reconstruction: A New Beginning

I know it's been a while since the last update but, you know, finals and the ends of the semester. However the summer semester for RCOS started a week ago (today was the second meeting) and I'm starting to get back into rhythm. And yes, I will be the only one up here of the group so we'll see how it goes.

Now to get you guys updated:
After careful analysis of possible issues that may have occurred during the Night of Transistor Smoke, I may have come to a conclusion. When designing the H-bridge, we rated our MOSFETs for 2.7 amps, the free current rating of the motors we bought. However, the actual current that the components need to be rated for is the stall current, which is the maximum current the motor will take when it's applying it's maximum torque given the load it is under. This is 133 amps. But as much as I would love to say I solved the problem, the motors weren't given a load when we were testing so I'm kind of hoping these new 150 amp MOSFETs do the trick, and yes, you heard right, new MOSFETs from Newark. These guys were even nice enough to give me a personal call to make sure I got everything okay. Classy. Check it out:

http://www.newark.com/international-rectifier/irl7833pbf/n-ch-mosfet-30v-150a-to-220ab/dp/19K8397?in_merch=Featured%20Products

I also decided to buy a couple inverter ICs just so everything can run off the same pin from the Arduino. Now, ladies and gentlemen, for the moment you've all been waiting for *cue drum roll*:


I know, it looks sketchy, but perfboards really hate 14 gauge wire and i just wanted to be safe this time. Anyways, I just need to solder on some battery leads and we're good to go (for now). I do in fact plan to get a custom board printed because when I say perfboards hate 14 gauge wire I mean they really REALLY hate 14 gauge wire. Plus I don't trust the fine traces with up to 133 amps so I soldered them thicker as well. So I guess that's all in the world of motor controllers for now.

Other things to be done in the not too distant future:
-Find suitable base-plate for Alfred
-Tune drink dispensing system

These items are planned to be done by the end of this week so stay tuned. For all you RCOS folks, I apologize for all the hardware but when this is done there will be a lot of Arduino code and Java coming your way.

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