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View Full Version : [Discussion] My Roboard: First Thoughts



WGhost9
04-14-2009, 02:11 PM
Well I have had a week to play around with my Roboard, and I thought I ought to share my thoughts on it and get a discussion going.

Pros: A very small board with tons of IO and yet all the IO is easily accessible. The library functions and drivers make coding quick and easy. Well priced compared to the Pico-ITX and the gumstix. The low power draw allows me to run it for many hours off of a single battery.

Cons: At 256k ram, it runs very slowly. The uSD card doesnít always physically connect to the card reader correctly and often requires multiple reboots to remove and replace the uSD before the BIOS sees it.

The Roboard seems to run OpenCVís basic functions (Webcam display, drawing, IO support, etc) quite well, but crashes on the more advanced functions (such as Classifiers, Face and object tracking), which is probably due to the limited available RAM. Looking forward I hope to write a slimmed down version of the object tracking that will still run with the Roboardís specifications.

Having previously using a gumstix running uLinux, I particularly appreciate being able to run a native XP environment. I am very concerned about the voltage level for the servo power lines. The Roboard seems to run servos at 7.5V, which seems a lot to me (I donít know what maximum current output it has). Has anyone found their servos burning out at 7.5V?

DresnerRobotics
04-14-2009, 02:18 PM
I've noticed the same thing with the uSD slot, but one of my previous Gumstix did the same thing so it wasn't unexpected.

What are you using to power the board?

The servo power isn't regulated onboard from what I found, if I gave it 12v it gave the servos 12v. 6v input gave them 6v.

lnxfergy
04-14-2009, 02:32 PM
256M ram, right, not 256k?

Oh, and thanks for the review! What was it that ended up being the issue with installing XP?

-Fergs

ScuD
04-14-2009, 02:36 PM
I know from experience at my last job that for each project over 12 (!!!) different uSD sockets were thoroughly tested by the environmental and mechanical team before they found the least bad one that still had a dropout rate of about once every 20 insertions or so..
The SIM/uSD combo connectors were even worse. Depending on the connector ofcourse, our trick was to put a small patch of scotch tape on the top of the uSD card making it push down just a tad harder on the contacts which helped a lot.

But then this may not help your problem at all..

Azinman
04-14-2009, 04:52 PM
I've run servos unregulated at 9V before no harm done from what I've seen so 7.5V shouldn't be a problem.

lnxfergy
04-14-2009, 05:24 PM
I've run servos unregulated at 9V before no harm done from what I've seen so 7.5V shouldn't be a problem.

That's not gonna be true for all servos.... or even similar servos in different uses.

Also, depends on the load on the servo, if you are building a biped and over-volt the servos, because they are holding more load, they will be using more power. Power usage means you have to dissipate heat... thermal overload is probably the quickest way to kill a servo.

-Fergs

DresnerRobotics
04-14-2009, 06:44 PM
I've run servos unregulated at 9V before no harm done from what I've seen so 7.5V shouldn't be a problem.

I've also seen a good amount smoke at 7.2.

Adrenalynn
04-15-2009, 01:11 AM
Yeah, greatly depends upon the servo. You won't run a 322 or 475 @ 7.2v with any kind of measurable load for long before they smoke. 9v into a 322 or 475 is a good way to let the magic smoke out with NO load. Even the electronics are gonna be fryin'.

WGhost9
04-15-2009, 10:58 AM
Well that is what I thought about the servos and voltage; I guess I ought to start building a heavy duty regulator for 6V.

Thats good advice about the uSD Scud, I'll try it out.

As for the XP install problem, it was never really clear what was wrong. Deductively, I suspect the DVD drive may have been at fault but I cannot be certian.

By the way if anyone else has run OpenCV on the Roboard, I would love to learn how they managed, since I beleive they are RAM overflow issues in OpenCV that are killing apps that otherwise run fine on other systems.

Adrenalynn
04-15-2009, 02:04 PM
Why not just pick up a Castle BEC? I doubt you're going to build a programmable switching regulator for less than you can buy theirs for.

There's no way the Roboard is designed for vision applications, especially with that hog that is OpenCV. Aint gonna happen. You need a computer for that, not some little controller.

jes1510
04-15-2009, 03:30 PM
I'll second the Castle BEC. I started to do the same thing and design a custom power supply capable of a few amps and came to the conclusion that I can solve the problem by throwing one twenty dollar bill at it. The thing is small and works perfectly. It seems to be a great product.

ScuD
04-15-2009, 04:33 PM
One more second.

A while ago (little over a year actually..) I started designing a power supply based on the LM2677.
Built me a protoype thingamajig
http://users.telenet.be/svendecock/robot/Power%20supply/teaser.JPG
but the amount of design issues that comes into play at these currents at high frequencies (>1Mhz) insure that it saves a lot of headaches with just buying the things.

Don't get me wrong, I'm probably the world leader in re-inventing the hot water, but some things just aren't worth it. Most people here *cough*Lynn*cough*know me well enough by now that I tend to jump into a project head-first and get distracted halfway through because of wanting to build stuff myself that's readily available on the market and thus prematurely scrapping the entire project.

Pisses me off.. don't make the mistakes I do..:veryhappy:

Adrenalynn
04-15-2009, 05:02 PM
Hey, reinventing hot water can be fun. As long as you don't NEED a shower this week. :)

I'm getting old... Or more respectfully - my time has value. "When you can walk on water - take a boat" I don't _need_ to reinvent anything. If you feel you do - more power to you. Just don't plan on having it working before the sun cools.

If something is crazy expensive and I can build it from scratch for 50% or less, I probably will. If it's perfect for the task and way less expensive than I can build it for, count on me to just buy it.

WGhost9
04-15-2009, 06:18 PM
Spending time designing power supplies is on issue I am torn on really; for >20$ I can make a 6V 12A supply that is quiet enough for electronics, but it takes some time scrounging. The trick is that old computer power supplies are through away parts now adays, and with a with heavy duty op-amps, one can solder the perfect supply together easily.

Adrenalynn
04-15-2009, 06:45 PM
Sure. For five pounds versus a < 1/16th of a pound. 6x8" versus the 2/3 the size of my pinkie finger.