using the UCN5804B controller IC from Allegro.
http://margo.student.utwente.nl/el/misc/stepper2.zip
http://margo.student.utwente.nl/el/misc/stepper3.zip
http://www.edn.com/article/CA293242.html
An electronic speed control for an AC Motor can be designed with a Light Dimmer IC by limiting the minimum firing angle of the triac so that the motor won’t stall.
http://www.lsicsi.com/pdfs/AN304.pdf
Steve Bolt came up with an interesting smokeless 4-transistor H-bridge variant, i.e. no combination of inputs can cause the bridge to self-destruct.
http://www.solarbotics.net/library/circuits/driver_4varHbridge.html
Devoted to the theory and practice of building H-bridges for controlling brushed DC motors.
http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/index.html
A method to determine the Linear Transformer Model parameters of a Neon Sign Transformer
http://hot-streamer.com/TeslaCoils/OtherPapers/TeroRanta/CurrentLimitedTransformers/NSTModel.htm
http://www.spelektroniikka.fi/kuvat/triacd.pdf