schematic error

I recall reading a message describing an error in the following schematic concerning resistors. http://arduino.cc/en/Reference/StepperUnipolarCircuit My controller chip is overheating. Any suggestions?

We're going to need more to go on than that! What is the current rating of your motors, to begin with?

Try this and the pages around it:- http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

The data sheet says nominal 24V, 30ohms. I have taken on a project well beyond my experience. Thanks for the help.

24V, 30 Ohms means that each winding will draw nearly one amp. You may need a bigger driver chip!

(I = V / R, by Ohm's Law)

Would you please suggest an alternative dirver chip?

Have a look at the L298, which will need external back-EMF protection diodes.

Is this the chip you are suggesting? http://mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMvHdo5hUx%2bJYj%2bwTDEc3W8U
Thanks again.

Yes, that's it. But looking at it again, it may not be the best chip for your application. You may need more outputs than the L298 can offer, and you may not need the full H-bridge function. The best solution might be to use a few discrete transistors or MOSFETs.