Hello all, These questions might seem very silly but it is my first time purchasing electrical components and I want to make sure I buy the correct ones based on my OWN LOGIC. I do not just want to blindly follow directions to build this motor controller without knowing the logic behind the parts that I need. A few weeks back I made a post about constructing a circuit to control the speed and direction of a DC motor. The link to what I have in mind is below. http://www.electronics-project-design.com/DCMotorDriver.html [Broken] Now, I know they have the components listed to buy, but my question is, how would I go about figuring out what to buy myself? What I mean by that is, if I was making this circuit from scratch without the aid of the website, how would I know what types of components to buy? I ask this because I want to have some insight into the design aspect of the circuit instead of just buying the parts blindly. My guess would be this.. -Find a potentiometer From that potentiometer determine the voltage ranges that will go into the Op-Amp. -Find an OpAmp and determine what is the maximum voltage the Op-Amp will put out based on the voltage ranges found. -Get two Transistors that have a base current requirement of the current coming from the Op-Amp. -Get an electric motor that will run on the current from the transistors. Does anyone have any good sites to purchases electronic components? Does Radio shack sell them? I found a site called http://www.mouser.com [Broken] it seems to be very good but I tried looked up potentiometers and they only had "digital potentiometers." I do not know about digital ones, the ones I had in mind were mechanical, meaning you turn a knob and it changes the resistance.