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Author Topic: Beginner's Robot HELP  (Read 895 times)

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Offline edwarricTopic starter

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Beginner's Robot HELP
« on: July 20, 2013, 10:41:14 AM »
Hi, I'm new to the world of robotics and wish to build my first robot. I've followed the guide to purchase basic equipment creating a BASIC robot, as it is my first.
My equipment would be this:
60 x 8mm pair of pololu wheels   (x2)
9.7:1 metal gearometer 25d x 48l mm (6V)   (x2)
6.0vdc 1600mAh NiMH battery pack
arduino uno
miniphotocell (x2)
a chassis, any advice?

Would this work, any advice, any more equipment?
Thank you for you time  :)

Offline waltr

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Re: Beginner's Robot HELP
« Reply #1 on: July 20, 2013, 02:45:56 PM »
Should work but you do need a motor driver circuit, Dual H-bridge.


Posting a link to each part you are thinking of buying is a great help so that we know exactly which part it is. Are these the parts:
http://www.pololu.com/catalog/product/1420
http://www.pololu.com/catalog/product/2271
With or without the encoder? Get the encoder if you can afford it since it can be used as feed-back to maintain speed and other uses in a Bot.
The 9.7:1 gear ratio give a maximum of 1000 RPM. With 60mm diameter wheels the Bots top speed is:
2 * Pi * 60 * RPM = 6.28 m/sec which is pretty fast for a small Bot.
This motor:
http://www.pololu.com/catalog/product/2273
has a max of 285 RPM so the Bot's top speed = 1.79 m/s which is better for your first Bot and the Torque will be higher.
These motors have a 6A Stall current so an H-bridge that can handle more is recommended. Like this one:
http://www.pololu.com/catalog/product/2502
or this one
http://www.pololu.com/catalog/product/707

« Last Edit: July 21, 2013, 08:27:04 AM by waltr »

Offline jwatte

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Re: Beginner's Robot HELP
« Reply #2 on: July 20, 2013, 07:22:57 PM »
I think the 9.7:1 doesn't give you enough gearing. The bot may have a hard time starting/stopping because the torque is low. I'd suggest a 25:1 or higher gearing instead.

You also need a motor controller of some kind. A "dual motor controller" or "dual motor shield" would be best, as it's easier to hook up, but a "single motor controller" times two also works. Just make sure it's rated for more than the voltage you use and more than the current draw (stall amp rating) of your motors.

When it comes to chassis, if you're not getting a kit (like the 3pi, Zumo, or another such kit) then the "best" chassis is simply a plastic plate (or plywood) that you can screw things into. Get mounting brackets for the motors to screw them into the plate, and make sure you screw them in straight!

Finally, with only two wheels, you will need some kind of follower wheel/caster. Unless the bot is specifically made to balance on two wheels like a Segway, in which case you will need an IMU of some sort (accelerometer and gyro, perhaps with compass.)

Offline MrWizard

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Re: Beginner's Robot HELP
« Reply #3 on: July 20, 2013, 11:52:09 PM »
Perhaps you have some Lego. That's how I made my first "pigeon-style" robot icw the $50 robot tutorial and some photovore "eyes". Lego is easy to experiment with. Integration with normal hardware is sometimes a bit difficult, but it is flexible and quick to prototyle with. Did I mention lightweight ?

Offline edwarricTopic starter

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Offline edwarricTopic starter

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Re: Beginner's Robot HELP
« Reply #5 on: July 21, 2013, 01:34:49 AM »
also, i do not have any lego, sorry.
my aim is to build the robot from the ' how to build a robot tutorial'.
autonomous, two-wheeled...
here's the link :   http://www.societyofrobots.com/robot_tutorial.shtml
thank you all again

Offline ROBOT420

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Re: Beginner's Robot HELP
« Reply #6 on: July 21, 2013, 09:10:48 AM »
So this will be a "self balancing" segwey style bot?
Don't know jack, but want to know it ALL....let the journey begin!

Offline edwarricTopic starter

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Re: Beginner's Robot HELP
« Reply #7 on: July 21, 2013, 10:00:25 AM »
that doesn't sound right.... hmmmm....  what ever is easiest as this will be my first robot

Offline jwatte

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Re: Beginner's Robot HELP
« Reply #8 on: July 21, 2013, 11:30:55 AM »
chasis : ???
any other equipment ?

thank you all for your time!  ;)

The time seems kind-of wasted when you didn't actually read the advice we gave you. You're missing something important, mentioned by at least two people above.

Offline edwarricTopic starter

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Re: Beginner's Robot HELP
« Reply #9 on: July 21, 2013, 03:04:13 PM »
sorry, but my reply was aimed at the first response where the user asked for my parts list, i had not read the other comments from that point :D

Offline edwarricTopic starter

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Re: Beginner's Robot HELP
« Reply #10 on: July 21, 2013, 03:05:24 PM »
thank you jwatte for your advice!   ;) Really helping out

Offline civrays

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Re: Beginner's Robot HELP
« Reply #11 on: July 27, 2013, 01:53:39 AM »
As mentioned above, you also need a motor controler, a dual H-bridge. This is the dual H-bridge that I used http://civrays.com/myrobot/components/motorcontroller

I too am from the UK and purchased this from ActiveRobots. It requires soldering, so if you are not confident to do that then you'll need to find a pre-assembled alternative.

Offline jkerns

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Re: Beginner's Robot HELP
« Reply #12 on: July 27, 2013, 06:29:58 AM »
So this will be a "self balancing" segwey style bot?
The $50 robot uses a skid instead of a third wheel
I get paid to play with robots - can't beat that with a stick.

http://www.ltu.edu/engineering/mechanical/bachelor-science-robotics-engineering.asp

 


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