Anyone received their EDUs already?

[codeoftherobot]

Our EDU finally came today. I thought FIRST were supposed to ship the EDU's out a while ago but at least they came. We were actually supposed to receive the EDU yesterday but it arrived today. Wonder what went on?

[Sachiel7]

We were actually supposed to receive the EDU yesterday but it arrived today. Wonder what went on?

FIRST used ground shipping.

I FINALLY got to the point of being able to compile and upload to the new eduRC. Whew.
And, the results are really cool. While we still don't have our R/C controller yet, I programmed it to do a few things. First off, I'm using my crab-drive edubot that I built before we got the new controller. I've gotten it to basically strafe around in different shapes, circles, triangles, squares, etc.
I'm having a bit of a problem w. the servos though...
The Range of the pwmXX variables is still 0-255, right? For some reason, The HiTec Servos from last year's kit wont go all the way around to 0 when 0 is sent, and wont go all the way around to the other end at 255. They do center at 127, though. I tried a few different things, but I'm still having some issues getting them to go from 0 deg (0) to 90 (127) to 180 (255). And Yes, I know that the servos actually have over 180 degrees of rotation, so these numbers aren't 100% correct, but the problem is that they won't move enough. I'm not sure why. In all my previous work with servos, I haven't had this problem...

Anywho, I'm trying to find a small portion of free web space I can link to to post up some video of the bot in action. We're still in the process of getting our "new" domain set up.

[seanwitte]

Are you sure about the servo range? I had a HiTech servo that only had a range of about 100 degrees.

[Sachiel7]

Yeah, I'm pretty sure, but maybe you're right.
The servos I'm using are from last year's kit.
Hey, It's good enough for me to get it to do a few shapes, so I'm fine for now.
I really like the fact that it can be programmed to run without any special equipment. I already have tons of auto modes programmed within just one day! And, you can switch betwen them easily.
I'm still searching for some free web space to upload some videos of the MiniCrab in action...

[AsimC]

I really like the fact that it can be programmed to run without any special equipment. I already have tons of auto modes programmed within just one day! And, you can switch betwen them easily

nice...so do i... but how do you easily switch between them? i just have separate .hex files.

[Sachiel7]

I use this method:

F_Count > Function Counter. This counter is set at the beginning, and performs a task based on it's number.

T_Count > The number in seconds for each task (F_Count) to be performed. This could be turned into an array for separate times per function.

counter > A temporary Cycle counter. The Main User Routines (17ms) loops about 58 times/sec. So, the main loop thus contains:

counter ++;

if (counter > (T_Count * 58))
{
F_Count ++;
counter=0;
}

Then, we simply check the value of F_count to define the robot's Current Functions:

if (F_Count == 2)
{
pwm01 = pwm02 = 254;
pwm03 = 0;
pwm04 = 254;
}

Now, I could use a switch instead of a bunch of 'if's, but the last time I tried the compiler didn't like it...
So, F_Count 1-10 could be one function, 12-16 another, etc. You need to alot one extra value check for each main function to reset it, if you want it to loop:

if (F_Count == 11)
{
F_Count = 1;
}

etc.

The way I'm currently switching between them is in the programming. I just change the F_Count's Initial Value, and T_Count's value accordingly.
You could easily set up your digital i/o pins so that you can install a jumper on a set of pins and it will trigger a certain auto mode. I'm working on something like that now...

[AsimC]

Now, I could use a switch instead of a bunch of 'if's, but the last time I tried the compiler didn't like it...

haha..yea i had the same problem w/ switch


anyways..thanks for the info..

[Andrew]

I just installed the software, compiled a program, and down-loaded the code. The down load only took a few seconds (10-15) much like the previous year's controller.

I originally tried to install using Crossover Office (under Linux). No real success.

I then attempted Windoze ME. OK on the MPLAB stuff. No success on the IFI.

Finally, I installed under Windoze98. All went fine.

Thank goodness they supplied us with the EDU controller and compiler NOW. I cannot imagine trying to deal with these issues along with everything else in the build phase.

I anticipate many late nights loading code into the EDU controller before January.

[marlon_jbt]

And haven't had much time to do anything with it yet...it's just sitting there.

I was amazed at the small size of the new contolller compared with the one from last year! Reminds me of that Subway guy!

[Pat Fairbank]

Anyone here in Canada gotten their's yet? We haven't.

[KenWittlief]

our team hooked the new EDU controller to an R/C system we had from a few years back (that we used for older robots)

I think its an AirTronics 4 channel FM system (will check later)

it worked perfectly - students had our EDU bot running around in no time at all, using the default code in the controller.

Personally I like the new hobbie R/C transmitter setup - it lets you put the whole EDU kit into a container (from last years game) and carry it around - and we dont have to share the Operator Interface with the full sized robot anymore.

and, now we have two Robot controllers for the EDU kit, the new one and last years, so you could build two robots with the one EDU kit, and have mini competitions if you really wanted to.

[Argoth]

ours came in today anyone know what the coeffecint of friction is for the wheels, i am guessing 2 or 3

[KenWittlief]

I checked the radio system we used - its a HiTec, not airtronics.

BTW - for the post above ^ the coeffecient of friction is always less than 1 - you cant have a stonger fiction force than the normal force, unless the material hooks or glues itself to the mating surface.

[Tristan Lall]

Originally posted by KenWittlief
BTW - for the post above ^ the coeffecient of friction is always less than 1 - you cant have a stonger fiction force than the normal force, unless the material hooks or glues itself to the mating surface.

Off-topic, but what's the rationale behind stating that mu < 1? As examples, here's a potentially contradictory explanation (http://mathforum.org/library/drmath/view/51493.html), and here's a spec sheet for sorbothane (a plastic foam) that neither adheres nor hooks onto any other surface (http://www.sorbothane.com/PDF/sor_matprop.pdf). They report a static coefficient of friction of greater than 15 under certain conditions!

[Mike Betts]

Tristan,

A "sticky" subject indeed. All references are correct. For most all applications, mu is indeed less than one, however, it is not a physical requirement.

As an example, I ask that you consider one of nature's most amazing substances... Water.

When a skater is gliding across the ice, the weight of the blade of her skate causes the ice to melt and this lubricates the ice/blade boundary to a very small value of mu.

Now for an old fashioned dinner table experiment. Take a standard teaspoon, clean both the spoon and the end of your nose with a clean napkin (this gets rid of grease). Next, breathe heavily on the spoon to create a light layer of condensation. Now you can "hang" the spoon off the tip of your nose demonstrating a mu of > 1.0 for the very same substance (water).

In our first example, water is a "lubricant" and in the second it is a "glue". Both actions must be examined on an extremely small scale to be understood.

In general, Ken is correct. For mu > 1 there is usually a hook or glue mechanism at work. Just remember, the action might be taking place at the molecular level...