MMM v3 BEC questions
 

So, a switching PSU for BEC is, basically, the reason I got the MMM. I want off the shelf ease and minimal components, and MMM gives me power for brains and for mechanics in one nice package.

The BEC appears to run at 5.84v which is damn near perfect for my needs :smile: and well within the range I can use for my robo-brain (Basically 5.5v to 9v with anything over 5.5v being spent in heat.)

My questions are:
1. Will voltage ever be programmable like the CC dedicated BEC?
2. What available amperages will the BEC provide at 8, 12, and 24 volts (or approximate voltages.)

My brains will use about 1a.

Picture of brains on slash, which is the PERFECT platform for junior robotics. It's the FIRST RC truck that has space for stuff so we can build OUT instead of UP (which makes most RC robots tippy.)

Not to mention, the slash is tough enough to survive going full speed during a stuck control loop! :yipi: I'm so happy with the slash.

http://www.coreyfro.com/rc10/zoom.jpg

Cue BrianG. action.

Looks like an interesting project! You're right; the Slash is about the only stock vehicle I know of with that much empty space on it.

1: As of right now, I would say no. The BEC also supplies at least part of the ESC brains with ~6v power, so any adjustments would have to be tolerated by those other components.

2: Not sure what the current output of the built-in BEC is, but judging by the components used, I'd say around 3A is a safe bet. And since it is a switching BEC, that available amperage is good for all voltages from ~7v up to the max of 25v. BEC efficiency doesn't change all that much with supply voltage - it's the load current that makes it fluctuate. And switchers tend to be most efficient at around 75% of their max current rating from what I've seen.

As far as getting stuck in control loops, you outta put in a manual override so you can use a remote (at least for the testing phase). I can just see people running after an out-of-control Slash trying to catch it! :smile:

I *think* Patrick once said that the MMM's BEC was good for up to 5A, but ran quite warm at that kind of drain. I could be remembering wrongly, though.

Looks like a cool project though! What are you planning to do with it?

Ahhhhhhhhh, makes total sense now. OK. if I have any requirements for higher voltage, then I'll use my CC BEC. I just want to keep the number of parts low and simple because this isn't for me, I'm trying to make a simple, standard, cookiecutter robot for RC nerds.

Yeah, I don't have a wireless kill switch yet.

I'm working on an off the shelf implementation of another project I (and about 20 of my friends) have worked on.

Orb Swarm is a network of 6 robotic orbs that communicate with each other and choreograph their own movement, music, and light show.

Each orb is about $6000 and MONTHS of work, not including the year and a half of software work...

...With this side project, I'm making swarmable robots accessible so we'll have more robots to swarm with.

I want to make it so any RC nerd unafraid of UNIX can make a swarmable robot out of any of their models, easily.

Imagine your local football field filled with 20 or more rc robots driving around in formation, blinking and chirping together.

Failing that, I'll at least have a software development platform for myself that roughly models the orbs because, at 80lbs and 30", they are a bit too large for my Corolla to haul. :neutral:

http://burningcam.com/2008/photo/pic...picture-49.jpg

Depending on the actual voltage you'll need, you can probably get away with using a linear regulator since you said you need ~1A. The loss in efficiency will be less and less as the regulator voltage approaches the supply voltage and/or the current goes down.

The losses is simple to calculate: power_loss = (supply_v - regulator_v) X current.

So, if you are running 4s and wanted 9v out, the loss at 1A would be 5.8w. A decent amount to be sure, but nothing that a medium heatsink couldn't handle. As a bonus, linear regulators can be "programmed" (via 2 resistors) to be at any voltage you want.

The disadvantage of linear regulators is power loss/inefficiency. The disadvantage to a swithing regulator (aside from cost) is the potential for it to go bad and send full supply voltage to your circuits. It doesn't happen very often, but is possible. I don't know how expensive that processor/circuit is, but something to think about. Linear regulators usually fail by thermaling, or going into overload shutdown. You have to really try to blow a linear regulator.

You peaked my interest, now need a video!

This video is from Sept 2007. It's the best video we have at night.

And here's our Media page

Did you stop and see Cyclovision while Castle was at Burning Man in 2007?

We did a 6 x 3 foot 3D projection system (picture 10,000 RGB LEDs rotating at 300 miles per hour creating a 1 million voxel viewing volume...) we called Cyclovision. It's still together, but we didn't make it to Burning Man for 2008 ('cause of the Monster issues...)

No! I tried to google you with no luck. Are you related to Cubatron?

I think I heard about Cyclovision, but I didn't get to see anything, I was busy working 4 F'N PROJECTS!

Steampunk tree house (I did a bunch of CNC plasma cutting for it, and helped with roll out but not setup)
Orb Swarm (I was the Playa Proof Puter/mothernode guru during the event)
Neverwas Haul (mainly my wife's project, but I hang out with them because they are serious about relaxing.)
Critically Single (Speed dating on wheels...don't ask)

I haven't simply ENJOYED the event in 4 years...and I've loved every minute of it.

Have you been to the Maker Faires? If not, you should go, especially since the sheer number of robotics nerds there is staggering and would probably be great bidness for CC.

I'm sure the voxel display would be great at maker faire, too.

I saw a bunch of CC signs at Robogames but I didn't see a booth.

Damn Monster!

Loved the Steampunk Treehouse! Richard and Jon and I look for the Orb Swarm the whole time we were there -- was one of the things we really wanted to see. . . but never caught it. My wife saw something similar (robot dogs that protected a camp area -- was pretty cool...) but I missed it...

Here's some pictures of Cyclovision (Sorry -- I don't mean to 'jack your thread!)

Cyclovision being put together on the Playa: (Look close and you can see the FPGAs and LEDs -- There is also 128GB of memory in the stack -- yes 128 GIGAbytes -- all the animation was stored in Flash)

http://i37.photobucket.com/albums/e9...t/IMG_3455.jpg

(The fat guy is me...)

http://i37.photobucket.com/albums/e9...t/IMG_3454.jpg

And some bad shots of some of the play: (1000 RPM rotation -- 3D images)

Synthia:

http://i37.photobucket.com/albums/e9...t/IMG_3495.jpg

Animated Fireworks:

http://i37.photobucket.com/albums/e9...t/IMG_3484.jpg

And BTW -- We will be at Burning Man in 2009.

So please, ask if you need any assistance for Burning Man projects.

That is awesome, and if I know anything about voxel displays, photos are several orders of magnitude less cool than seeing it in person!

I was lucky enough to learn about SPTH very early on and, when I first heard about it, I thought "That is EXACTLY the best platform from which to propose to Hallie!" I worked my rear off to make that happen.

That story is here. We got married at Maker Faire in May.

I'll let you know of Orb Swarm does gigs any time soon, we do travel nationally. I think we are all gigged out at the moment.

As far as how CC can help, I don't want to ask for hand outs, but if I think of anything, I'll let you know.

I will say that I envision the MMM and a low KV motor as the item to pick for the "Off The Shelf Swarm" and once I get further on this project, since we are totally open source, you are free and invited to bring your own swarmable bots to play with ours.

If I had to make a wish, however, if there was anyway to get an RPM count out of the MMM (for robo dead reckoning) it would be a huge boon for robo-nerds everywhere.

I've though about simple watching and counting the pulses off the motor leads, but I haven't played with that yet and it does go a little against the "off the shelf"ness of the project. I know that I cannot expect this project to be without work from the user, but I wanted to reduce that as much as possible.

Dead reckoning is one of about 6 of the inputs to our kalman filter for orb swarm. I know it's noisy, but it's very important for keeping our GPS readings sane.

If you are ever in SF, lemme know. Coreyfro@coreyfro.com

OH. So the theme this year is Evolution, and Flaming Lotus Girls had "Mutopia" last year. Big f'n plants that shoot fire. We're thinking Mutopia would be perfect for the Evolution theme, and we're brainstorming ways to make critters for Mutopia. Maybe 1/18th scale trucks disguised as cockroaches are in order! ;-)