Does anyone know of any simple circuits for driving stepper motors? I have both uni- & bi-polar and a little knowledge of electronics. Something very basic is all i want - something I can actually understand how it works. What are the best ICs? Can a simple transistor circuit be used with no ICs?
The simplest and cheapest way to drive a stepper is to use a dedicated IC.
L297 and L298 will allow you to plug and play about as cheaply and easily as possible. The days of using discretes to create a stepper driver ended once ASIC's such as 297/298 came into existance.
I have a "discreet" based stepper motor driver on one of my machines. The circuit board is rougly 6" x 9" and it has a quad op amp and 5 TTL IC's and a small gaggle of resistors, diodes and monitoring led's.
The whole mess is now incorporated into the footprint of the L287 and has more protection circuits and higher performance. IF you're trying to make a cheap driver, building your own may not be the most cost effective way to do it.
There is a DIY driver thread on this message board. Can't recall the link.... but the guy who made it trades the necessary stuff to run the card for beer and/or hot food (seriously)... Check it out.
There are no simple circuits that works well. You need a chopper drive. Unipolar drives are much more fool-proof than bipolar ones. Hobbycnc has some good kits. If you prefer, you could do your own board using the same allegro chip that they use.