Hi from South Africa, a little help please

[Neale]

Something that I didn't find obvious when I first started looking at stepper motors is that their voltage rating is actually pretty much irrelevant. That's why, for example, my machine uses a 68V power supply to drive nominal 4V or so motors! What you are looking for is rapid motion and adequate torque, and in practice this comes from current. You are aiming to push something like the rated current through the motor during the whole of a drive pulse, and given their inductance that means a high voltage via a current-limited driver. If you look at the specs of a typical stepper driver, you will see that it has the ability to set max drive current but output voltage isn't mentioned. My concern with what you have built using a 5V power supply is that you won't have the current drive capability, that is, the ability to drive the rated current through the motor during the whole of a short pulse. You will be able to generate enough current to hold the motor in position but not enough to step it fast under load. I've never looked for published stepper driver designs but maybe that would be a source of more design info?

[edit] Just been taking a look at the L298 datasheet. Looks as if it can accept something like a 36V supply, and at least a couple of amps of motor current. That would probably be fine for the Nema17 motors in your machine. My 3D printer uses (from memory) Nema17 running off 12V but that's a pretty undemanding application in terms of speed and torque. The L298 actually has two supply voltage pins, one for the logic circuitry and one for the switched motor supply, so it's designed to work in that mode. (Hope I haven't misunderstood your original question and just told you a lot of things that you know already...)