Let's Make Robots!

List of good online shops for bot parts

I was wondering where online most of you go to shop for parts? Can we construct a master list of important websites here?

This list is from the URLs I've gathered from the various tutorials:

Picaxe 18 and Ping

I just picked up a Parallax Ping distance sensor from my local Radio Shack and am trying to figure out to how hook it into my Picaxe 18 project board.

The ping uses a single pin for both input and output.  It first requires a trigger pulse to be sent and then it responds with a variable length pulse that determines the distance.  Can a Picaxe pin be switched from output to input?  If not, can I connect 2 pins to the single Ping pin?  Normally I would jut go ahead and try it, but I don't want to fry my Picaxe or the sensor.

Where can I learn more about capacitors?

One of the things that still baffle me today is when to use and how to select the correct capacitor.

I've read through this chapter about capacitors: http://www.allaboutcircuits.com/vol_1/chpt_13/index.html

Afterwards I feel I undestand how they work, but still don't have the two most basic questions answered: 

Sharp Range Sensor gives inconsistent results

I'm trying to use a Sharp range sensor (http://www.pololu.com/catalog/product/136) on the Picaxe 18x project board but I seem to be getting bad results.  When the sensor is not facing anything within range, the analog input jumps around 95 - 110 in the debug window.  When an object gets closer the results seem to be more accurate, but still jumps around a little bit.

Not sure how to use the Picaxe 18x Project board

I just got my Pixaxe 18x starter pack in the mail (YAY http://www.sparkfun.com/commerce/product_info.php?products_id=8326) and the one thing that seems to be lacking is complete documentation. :)

All the output pins seem to go through the darlington driver and the pins coming from it are all negative (-) -- not positive (+).  Usually when you set a pin to "high" it goes positive, right?  This seems to reverse that.  I'm not exactly sure how to connect this to the motor driver or do serial output.   I hope this question makes sense.

Which Battery Pack for the PICAXE 8 Pin Proto Kit? (9 volt?)

I just received the PICAXE 8 Pin Proto Kit from Sparkfun (yay) and it comes with what looks like a 9v battery snap clip but the datasheet says that I cannot use a 9v battery.  The text states:

"ONLY USE A 4.5V or 5V battery pack, not a 9V PP3 battery, as the power supply."

So what kind of a 4.5v or 5v battery packs uses the snap type connectors?

How can I add Wifi to my robot?

I'm new to robotics but have dabbled in Microcontrollers the last few years and develop software for a living. One thing I've been dreaming of doing for awhile is builting a blimp robot that is controlled over wifi, but I can't seem to find information on is how to connect microcontrollers to some sort of wifi interface. I'm hoping there's some sort of module somewhere that I can interface with.

Here's the plan: