Let's Make Robots!

Need help with starting arduino robot.

I got an arduino for christmas and been learning to do stuff with LED and buttons.  So now I want to do a robot.  So what I wanted to know is what all would I need to do it.  I know a sharp analogue sensor, 1 servo to mount it on, and two grear motors with wheels.  So is there something else I need.  Like a motor controller or something. 

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also it have no ball bearing so didn't know if that will make a different, thanks

Airtronics 94102 Servos be any good to move a simple robot.  I'm thinking about going to pick a couple up here just a little bit when the store open up.  They are only $11 so I figure it would be something to get started with and then I could upgrade later down the line when I get a lot better.  This is my first robot so want to keep it very simple so here the specs on the servo:     1.59 oz weight    1.54 x 0.79 x 1.42 

4.8v  42 oz torque   0.20sec 60degree

6v   53 oz torque    0.16sec  60degree

 I just want to check if that will be strong enough to get my robot to go.  I'm not planning on making it really heavy. Just enough to hold the Arduino, sharp sensor and a servo.

Sounds like it could work, but will need modification to be turn beyond the small arc servos normally cover. As Frits has shown here with a GWS servo to modify.  HiTec servos are known to be easily modifiable too. I can't recall seeing an Airtronics being modified, but it is likely to be ok.  The HiTec HS-311 has been shown to be 360 modifiable at ServoCity and costs $8.99. It has a little less torque than the Airtronics above, but still should be fine to move the small robot described.
I already know how to modify that servo thats why I'm wanting to get it.  I just wanted to make sure if it would be strong enough or if I should look for something that have more torque.

or try ladyada's motor contorl sheild here


i have had some good luck with that shield and my arduino.....

do you know of any good motor controller you can build for cheap.  I do know there is one on here, but didn't know if you were able to build one that hold up pretty well with the arduino.  I have looked at the arduino site for servos and it seem you can just plug it up but in that case you would have to modify the servo I would imagine to get full forward and backward motion.  Thanks for your help.  I'm trying to get stuff rounded up so I can get it order.

That link that I posted in my last comment has a schematic for a cheap and robust motor driver. Like I said, that's what I use all the time, you can control speed and direction with only 2 pins. As far as your servo research went, your right. If you want to use a servo in place of a motor, you have to modify them for contiuous rotation. There is plenty of documention on modifying servos, but it's irreverable. 


Yeah, your going to need a motor controller, cause you can't connect the motors directly into the arduino because that would be unsafe and you'd likely damage the arduino. You can either buy one or build on your self using a SN754410 or equivalent. I use the same one for all of my builds, the information for the one I use can be found here: http://www.societyofrobots.com/member_tutorials/node/160


Now more on the general idea of building a robot with the arduino. You basically know everything you need to build a basic robot. Just hook everything up and code it. For coding information visit the arduino website at www.arduino.cc