Simple electromagnet

Using Arduino Project Guidance
#1

Hello - I have a simple application that I am looking at, trying to turn a series of small electromagnets on in sequence (not very fast). The intent is to pull an object along a track. Any suggestions on:

  1. Where I can buy small electromagnets?
  2. How do I interface them with the Arduino? Do I need to use a controller of some kind to provide the necessary current voltage? How many electromagnets can I control with one Arduino board? I would like to control 6 electromagnets.
  3. Are there any products out there that interface directly with the Arduino? One I have found is the Grove electromagnet.
    http://www.seeedstudio.com/wiki/Grove_-_Electromagnet
    Is there anything on the sparkfun site that is similar?
    Thanks for any suggestions.
    -Gaurav
#2
  1. Don't know. Can wind your own, iron nail and magnet wire.2
  2. Use a transistor to control current going thru the magnet wire. Use the 6 PWM pins, 3,5,6,9,10,11, so you can control the amount of magnetism with analogWrite( ).
    You also create PWM in software, so I would say 20 magnets without resorting to additional external logic.
  3. Transistors interface directly with Arduino. AOI510 has very low on-resistance (Rds).
    Q1 on the Grove electromagnet does the same.
#3

Be careful with electromagnets around your hard drive.
I don't get any hits for electromagnet products at sparkfun,com

#4