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Old 12-30-2011, 04:11 PM
Timcallinan Timcallinan is offline
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Questions about batteries, motors, microcontroller

Hello all,
Im starting to teach a robotics class this January and I have a couple of questions. I really appreciate any assistance or advice.
Question 1: We bought 10 classroom kits and some extra bits and pieces we bought 10 large sears toolboxes to store each kit. My question is about keeping all the batteries charged. The plan is to have 10 groups of 2 students so I need to make sure all the batteries for the micro-controller and batteries for the vexnet joystick are fully charged. My plan is to have a corner of the class-room with the 10 chargers just sitting there and when the groups are finished for the day just to plug them in themselves. Does this sound OK? Or does anyone have an organized method for making sure the classes batteries are charged when they are needed?
Question 2: During the first few weeks of the class I want to do the gear exercise from the Carnegie mellon curriculum. Basically in this exercise you use a motor with different gear configurations to lift a load of different weights. Here is the link if im not explaining it too well
http://www.education.rec.ri.cmu.edu/..._cnstrctn.html
My limited experience would tell me that there is a chance of burning out the motors Im going to have 10 groups doing this at a time so there is a potential to damage a lot of motors in 1 go. Will the provided clutch stop the motor getting burned out? Is this exercise safe for the motors????
Questions 3: The class Im teaching is for a community college so I feel I need to go into a little more detail with certain areas of robotics. Im specifically looking for notes or a good tutorial that goes into more detail about the actual insides of the microcontroller. Maybe I need to find a good tutorial on general microcontrollers????
Thanks again for any help and happy new year...
-Tim
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Old 12-30-2011, 06:02 PM
bobsalive bobsalive is offline
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Re: Questions about batteries, motors, microcontroller

I'm working on starting up a class at the moment as well, so hopefully this can be of some help.

Q1: That sounds like a good plan, except you probably want some spare batteries. Since you're using the classroom kits, the robots won't be undergoing too much load and won't be drawing too much current, so you can probably run the batteries for a good hour and a bit (I'm assuming you have vexnet joysticks with AAA batteries and AA batteries for the robots). You definitely will need spares though, as having to tell the students that they can't use their robot because you ran out of batteries is pretty terrible.

Q2: Clutches can help if you're using 3-wire motors, but the classroom kit comes the protobot kit which comes with 2-wire motors now which supposedly don't need clutches. Given that the robots will be light, and driving a very small load, the risk of the motor burning out is going to be pretty small. The instructions in the link you gave also gear the motor right down, which takes the load off the motor so the risk of burning out the motor there is low. Personally, I wouldn't be too worried about it - just keep the weights low if you're worried about it. However, as with the batteries, it's probably a good idea to have at least a few spare motors, as occasionally if you're unlucky there might be a dud motor and at other times they can just inexplicably break (there is always a small, no matter how minute, chance of manufacturing defect).

Q3: Unfortunately you might have to write your own if you want to be specific to vex - I had a good look on the internet and didn't find anything that useful. As far as most teams are aware, it's just a magic box, that given the right inputs and outputs and with code (or in some cases with the default code), will make the robot move. That being said though, there is plenty of information available on the microcontrollers on the vex wiki website. Cortex: http://www.vexforum.com/wiki/index.p...icrocontroller. Otherwise, sections 1 and 2 of http://www.howstuffworks.com/microcontroller.htm are kind of useful for writing up a short tutorial as well.
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Old 01-15-2012, 08:19 PM
Timcallinan Timcallinan is offline
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Re: Questions about batteries, motors, microcontroller

Hi Andrew &co,
I'm starting a robotics class this semester. The first class has 20 students and will starts this Friday evening. I made a little video showing a bit of my setup.
If your interested, have a look. Thanks for your advice so far....
http://www.youtube.com/watch?v=0V1Iy...TDKACcdetTLId3

-Tim
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Old 01-17-2012, 04:54 PM
bobsalive bobsalive is offline
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Re: Questions about batteries, motors, microcontroller

Looks like a great setup! Good luck for your class!
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