Hello all, I am looking to build a robot and was just wondering if everyone could look at my list and see what I am missing, even if it is something as simple as a wire I have missed, please tell me! I hopefully have most of the parts I will need, but I'm doubting myself which is why I'm asking on here. It is just a basic, obstacle avoiding robot however I hope to add extra things in the future.
Arduino Mega 2560
400 Points Solderless Bread Board
Wires (male to male/f-f/m-f)
Ultrasonic Module
TowerPro SG-90 SG90 9g Servos (for the Ultrasonic module)
Continuous Rotation Servo & Wheel x2
4x AA Battery Holder (with batteries)
Third wheel for balance, no motor
Chasis (Building myself)
Thanks all.
instead of a third wheel
use a caster.
also, if you can get a bracket to mount the us sensor it will make life easier. you can always fabricate something, but there’s a model for 3d printing. I just ordered this one from shapeways… http://www.shapeways.com/model/1340814/servo-mount-for-ultrasonic-sensor-hc-sr04.html?modelId=1340814&materialId=6
I haven’t gotten it yet, but I’ll let you know if it works when it gets here
Wheels for Servos…
I like these personally http://www.pololu.com/product/1191
I have 4 of them and have used them in the past.
You can get ones with optical encoders on them too.
You want inexpensive?
I have read that drawer knobs are inexpensive. 
http://www.alibaba.com/product-detail/Wood-Turning_598395374.html
Check out the you may also be interested in images.
I saw this during my search.
http://www.hardware-online-store.com/images/CrystalKnobs/D30mm-Free-shipping-K9-crystal-glass-pink-funiture-drawer-knob-crystal-glass-cabinet-knob-241.jpg
EDIT: for whatever reason the image doesn’t seem to want to appear inline
It looks like a perfect fit. Then I looked at the product page. It is over an inch in diameter (30mm). Smaller would be better, I think. The biggest issue is the $125 USD for one. 
