Hello, I am trying to create a PWM circuit but I need a couple controls with in it. I need to control frequency and pulse width (duty cycle)seperately with 2 pots. This is going to control a spring loaded electromagnet for oscillation. I need pulse width control because of the varying elctromagnets it will be connected to at times, and the loads they will pull differ also. Here is a site I have been looking at they mention a 556 and a FET. but he mentions it not absolute on/off. I think with what Im doing I would rather it be absolute on/off. http://casemods.pointofnoreturn.org/pwm/circuit3.html There is a example of a 555 w/ opamp. In this schematic can I just put a pot in place of RF? If so wouldnt the pot work in reverse? ie as it turns counter clockwise it speeds up? If so are there reverse resistance pots? Im just a car audio tech. I dont ever work with IC,s. Resistors caps and ,diodes is all I work with. Can someone recommend a way to learn basic electronics, I know a 555 is basic and I should know how it works and how to use it.Most of the stuff I learned is just past the MECP guide, ohms law, just figuring curent, voltage, resistance...No IC training. Is taking a class easiest or are there books out there that would work as well and quicker.recommendations?