Saturday, January 29, 2011

XPWMShield V1.1: ...??

According to UPS tracking my Advanced Circuits order was delivered yesterday at 12:47pm and signed by a fellow named "WILSON." It's true, I could see the truck out my window! Regrettably, somewhere along the 100ft path from that truck to the front desk of South Campus Commons 1, the package was vaporized. It was never logged and nobody knows where it is. All I can say now is WIILLLSSSOOOOOOOOOOOOOOONNNNN!! And some four letter words which I already shared with the elevator and don't need to be shared here. I'll wait a few days before re-ordering, ugh.

Sunday, January 23, 2011

TOBL: Teaser

What happened to TOBL?? Well it's alive, better than alive. In an effort to actually finish the thing before returning to school I focused more on the building and less on the documenting. It was close but I had to take it back with me to school:

What's up TSA?

I used 1-1/2" Dubro tail wheels for the drivetrain, mainly because they have ridiculous grip and aluminum hubs. To my surprise, the smallest outer diameter of the hubs was ~0.401". To support the steel standoffs I bored them out to 3/8", so that's like 0.013" wall thickness or less at the very center. We're good though, the two halves didn't torque themselves apart on the lathe. The hub diameter just barely supported the gear-mounting holes as well, but they don't post these dimensions online so not my fault.

This just looks goofy.

Small snack for the mill.

After making those aluminum plates I thought lasering some out of acrylic would be cooler. It was good milling experience still, I guess? It took a few tries to adjust from the gears' theoretical to actual pitch diameter -in the end an extra 0.02" radius. The servo-gears are also not properly supported i.e.they are cantilevered off of the spline gear. So they wobble, just a little. Enough though that the servos stalled and stripped some teeth internally. This was actually a good wakeup call because the stronger HS-82MG motor wasn't designed with the HS-81 plastic gears in mind. New gears are on the way, enough to bring two HS-81s to life.

Not even including the set that actually made it to production.

Look for test footage next post! (waiting on parts in the meantime :/)

Monday, January 10, 2011

XPWMShield V1.0

After a long wait (it says 2010 on the board because it was sent out last year!) XPWMShield has arrived from AdvancedCircuits. And with a bag of microwave popcorn in the packaging? Awesome company.

XPWMShield V1.0

This revision of the board lived a short life. I only got it yesterday, soldered on all the components today, and just broke it five minutes ago. Before that though here's V1.0 in all its glory, running off a 1300mAh, 7.4V, 2-cell, LiPo battery I got off HobbyKing:

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She lives.

Need a better camera.

Just as I was going to test the wireless, one of the leads from the battery touched the bottom of the board, contacted a pin/via and blew up a trace coming out of the voltage regulator. Great. But at least the $34 Arduino Nano and $24 XBee are alright.

As it turns out the diode I put in between the XBee DOUT and Arduino RX was disabling radio communication. I put it there so that the software could be updated wirelessly without having to remove the XBee. So, I removed the diode and soldered a wire in its place -the same for the busted trace.

Ghetto wiring aside I can't complain, it works really well. With some minor revisions it's time to order more for future projects!

Saturday, January 1, 2011

TOBL: Quick Software Update

There was an issue controlling both servos at once. With one fader value being sent over to the Arduino one servo would work fine. With both, that same servo would tweak out. After isolating the error to the Processing side, it turns out the float defining the fader values was preventing the second fader from registering. With that cleared up the code finally works as intended*!

* The interface needs some work to be more user friendly. For example, a deadband at the neutral position so you don't have to land the fader on the exact pixel that corresponds to STOP. Also, there's a point - about halfway through the range - where there's no noticeable change in speed. Playing with the fader ranges in the touchOSC editor should fix that. My only other complaint is a little lag in feedback due to the speed of wifi. On the other hand, it can be controlled from anywhere in range of the network aka college campus, so we'll let that slide.