Collection of supplies

[gamefreak]

Alright well im planning on building a fairly big robot(i figure it will be simplier then a small one), now as i was recently trashing much of the junk in my garage i took apart a shelf made out of a failry heavy wood, now this comes with the fact that the only motors i have: are a small stepper motor, 3 continous rotation servos, and 2 180 servos

Where would be the be the best place to get better electronic motors for this project, my robot "brain" is going to be a Basic Stamp on a professional development board made by Parallax, i also figure im going to need a motor controller since these bigger motors require more current then 5 volts and anymore then 5 volts will damage my board

[Brandon121233]

Whats your price range? I would look at Banebot gearheads http://www.banebots.com/c/GEARMOTOR

[gamefreak]

well im rolling in about 100$+ a week, and i have a small amount of support from my parents,

so as long as the total price is under 750 $ i'll probably be fine

[Brandon121233]

I'm not sure how heavy your bot is but I would look at something like these http://www.banebots.com/c/MP-28XXX-385 or http://www.banebots.com/c/MP-42XXX-550, just find what ever speed you want the bot to go and with what diameter wheels, and pick out the gearmotor with the closest RPM. And by the way if your robot is not too heavy, you might want to get even smaller ones, because those gearheads are monsters outputting lots of torque, and will gobble down small batteries in no time at all.

[gamefreak]

those could actually work, since my board's IO pins can survive up to 5 volts i could use those motors and hook up a resistor, this site has a resistance chart somewhere, right?

I think im going to go buy a lighter wood at Home Depot or something because the wood i salvaged from the shelf is heavy and thick.

[Brandon121233]

WOAH! are you talking about directly hooking up the motors to you microcontroller board? If you are, stop right there, you would need a pretty large motorcontroller (H-Bridge) to power those motors, and you would need a secondary power supply to feed them.

[gamefreak]

see im clueless

but those motors only require from 3 to 9 volts, my board can supply up to 5

im think im going to go for a simplier solution and just make the bot smaller for now, i'll probably need motor controllers still, got any links to cheap ones?

[Admin]

Alright well im planning on building a fairly big robot(i figure it will be simplier then a small one)

Just a word of advice, speaking from experience, big robots are harder than small ones

I have this rule: as you increase the size of a robot linearly, you increase both the complexity and cost exponentially.

I highly recommend calculating your required torque before spending $100+ on motors, and expected current before spending $150+ on a motor driver

[gamefreak]

so far i figure im going to go out to Home depot and buy a light, thin(ish) wood, cut that, weigh it, weigh my board, and then find the torque i'll need to carry it all(with some extra torque so i can add stuff later on)

does this make for a sound plan?

[hazzer123]

Your microcontroller may be able to supply 5 volts, but it wont be able to source enough current for the motor. I think the pins on a MCU can normally source about a couple of milliamps of current. Motors, especially big ones, take huge amounts of current (up to a few amps).

How big are you planning on making this thing?

[Admin]

so far i figure im going to go out to Home depot and buy a light, thin(ish) wood, cut that, weigh it, weigh my board, and then find the torque i'll need to carry it all(with some extra torque so i can add stuff later on)

does this make for a sound plan?

I usually design the entire thing before I spend a single penny . . . cause you gotta weigh in the heavy batteries and motors, too. Even wheel diameter is important when it comes to torque and robot velocity.

If you know the density of wood and the shape (volume) of the wood, you can get a good estimate of the weight without physically weighing it. My CAD program calculates the volume of everything, so I just enter in the part density and it gives me the weight of my robot. I tend to do most of my calculations and optimization in excel . . . it might take a while to understand it all and go through all that work, but believe me its worth it in the end. And after you understand the math, its much easier the second time.

What if you buy an expensive motor that didnt have enough torque after you built the entire robot? Thats why I do the math

[Brandon121233]

For a robot, wood is rarely a good building material as it tends to warp slightly and warping doesn't do a robot any good. I would consider getting at least acrylic and most likely polycarbonate (lexan) for your base, Lexan is about 100X better for making robots than any other material.

[Admin]

except that lexan is crazy expensive . . . I recommend HDPE or acrylic

[Radiken]

You can always do what I did:
Go to a culinary supply store and buy a plastic cutting board.

[Brandon121233]

I build my robots to survive a drop off the empire state building, or being shot at.

[gamefreak]

i've never done any shop work on anything other then wood, i recentyl bought a firaly decent Miter Saw at a garage sale that came with a metal blade and a wood blade, Admin what CAD do you use? i've worked with AUTOCAD for my whole school year(i didnt use 3D) and i dont think AutoCad has that.

I tried to find a good robot simulator so i could test out my "materials" before buying anything but the only one that everyone said i should use was for linux, when i try to partition linux to my system by resizing my C Drive i get a messsage that says i might lose data.

[Admin]

i've never done any shop work on anything other then wood, i recentyl bought a firaly decent Miter Saw at a garage sale that came with a metal blade and a wood blade, Admin what CAD do you use? i've worked with AUTOCAD for my whole school year(i didnt use 3D) and i dont think AutoCad has that.

I use AutoDesk Inventor 3D (made by the same company that made AutoCAD).
If you can work wood, then you can easily work plastics. Just pick a sheet up from home depot and play around with it.

I tried to find a good robot simulator so i could test out my "materials" before buying anything

?

[gamefreak]

Can i use autodesk to build and animate a physics enabled robot and see how it reacts in an environment? or does t just weigh it for me?

[Admin]

I use v7 which is a few years old, and it has no physics engine. It can calculate center of mass, center of volume, weight, etc. But no physics.

Im not sure if v11 can do physics, but I doubt it.

If you expect your robot to go slow, or weigh under like 3 pounds, dont worry about the physics stuff.

Microsuck Robotics CrashStudio (cause the software crashes too much on me) has a free 'powerful physics engine'
http://msdn2.microsoft.com/en-us/library/bb483076.aspx

If you use it, let me know your opinion of it cause I might try it again . . .

[gamefreak]

i was watching soem of the videos of Autodesk, and it appeared that it can calculate gears and how they work/mesh with each other, is this ture? or is it just a fancy animation?

edit: there is no free trial, and it costs 5000$, lol way out of my price range

[Admin]

oh, another physics engine you might like to try:
http://playerstage.sourceforge.net/index.php?src=gazebo

So v7 I think can do part collisions, but Ive never been able to do it successfully. What I normally do is just tell stuff to rotate over a set period of time, like I did here:
http://www.societyofrobots.com/robotforum/index.php?topic=1218.0
(no physics, just motions)
Simulating that was great cause I was able to figure out what the camera on the robot can and cant see before it collided with the chassis.

If you time it right, you can make gears appear to mesh together in an animation. But I wouldnt bother with gears, I see no reason to animate that when you can just calculate it with paper/pencil.

With my robot fish (which I cannot show), the side (pectoral) fins flap in tandem in my animations.

I was also once able to do a 4-bar linkage motion, but v7 was just really flakey when it came to handling part constraints.

[gamefreak]

yea i think that is for linux

hey is this:http://www.journeyed.com/itemDetail.asp?itmNo=22061123NF&pres_view=specs
The inventor?
on the autodesk website the only purchasing option is for 5000$ where as this is 500$

so what all does this program do besides modeling, weighing, and gear physics?

also with this:http://www.autodesk.com/us/inventorseries/streaming/ais_inventor_studio.html
is it that the hydrulic is affecting the other thing? or is it just an animation of turning?

[Admin]

hey is this: http://www.journeyed.com/itemDetail.asp?itmNo=22061123NF&pres_view=specs
The inventor?
on the autodesk website the only purchasing option is for 5000$ where as this is 500$

yeap, that is the newest version. newest because its dated in the future
its cheaper because that is the student version (as if students can afford $500 . . .)
i like how this version can do wires, cause v7 definitely cant

so what all does this program do besides modeling, weighing, and gear physics?

animations, measurement sheets
http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=8410468

also with this: http://www.autodesk.com/us/inventorseries/streaming/ais_inventor_studio.html
is it that the hydrulic is affecting the other thing? or is it just an animation of turning?

turning

[gamefreak]

whats the difference between the academic version and the real version?

[Admin]

Im not really sure . . . if you find out let me know, Im considering buying the newest version for work. I really really need those analysis and better animation features.

[hazzer123]

Is it not just the licence that you get?

If you use the student edition, it can be for education only. If a company plans to use it, and will make a profit etc, then the real version must be bought. Thats the only difference.

I think so...