I'm confused about stepper motor voltage

gnydick

@deckingman, so is it possible to run 1 PSU for the motors and 1 for everything else?

deckingman

@gnydick I don't see why not but someone more knowledgeable than me might say otherwise. I'm fairly sure that the Duet boards switch the 0v side of things like fans and heaters. So you'd connect one side of your 24V heater to the 24V PSU and the other side to the Duet heater -ve terminal while supplying the main board with the higher voltage PSU.

dc42

@deckingman said in I'm confused about stepper motor voltage:

So you'd connect one side of your 24V heater to the 24V PSU and the other side to the Duet heater -ve terminal while supplying the main board with the higher voltage PSU.

Yes that's correct.

gnydick

@dc42 I don't have the confidence to wire things without foolproof instructions/diagrams.

For example, when I hear something like the fact that there's a common ground and I can use any of the negative terminals, makes my eyes water. I have 2-3 years of EE from high-school 30 years ago.

And I'm using tool distro board + 4 toolboards. Only heater directly connected is the bed.

jens55

@gnydick, Danger Will Robinson, Danger, Danger
Most of the outputs are SWITCHED on the ground side. They are NOT common !!!

deckingman

@gnydick In your OP you mention people using 48V to get "crazy speed and torque". If you are uncomfortable about making the necessary changes, then I guess the question you have to ask yourself is how badly you want that "crazy speed and torque". You can't print at "crazy speeds" due to restrictions imposed by the volumetric melt rate of the hot end. If your machine is for cutting metal, then you are restricted by how fast the cutter can remove material. So the only time you can use "crazy speeds" is for travel moves. How badly do you want to use higher travel speeds than those that you can get now? Torque is another matter. It is needed to accelerate the moving mass. So if you have a particularly heavy print head or cutting spindle, and you want to accelerate the gantry on which it sits faster than you are currently able, then you need more torque. But again, can you reasonably make use of that extra acceleration? If so, and given that you are uncomfortable with making the necessary wiring changes involved with using higher voltages, then there are other ways such as simply using bigger motors, or use remote drive shafts and asymmetric pulleys to get a gearing effect, or use two or more motors.

But you really need to do your own cost/benefit analysis (and for cost, I mean time as well as cash). Start with the benefits and look closely at how yould benefit from "crazy speeds and torque". Can you reasonably make use of them? How much would the printing or machining time be reduced? If yours is a commercial enterprise and the machine is running 24/7 then saving a few minutes out of every hour might be worth the cost. But if the machine sits idle for large parts of the time, then probably not.

gnydick

@deckingman that's all correct. My print head is heavy because it's the E3D tool changer setup on a RailCore II. I don't want crazy speed, just a bit more torque. I was merely referring to what happens at higher voltage to see if I could benefit.

I'm not uncomfortable making changes if I know what they are. The lingo is just too casually bandied about sometimes to be sure what people mean. Give me a diagram or explicit instructions, and I can do it.

It's when it comes to terms that aren't identical to what's in the duet docs that I'm not sure. Like, what's Ve? I remember VIN, VOUT, positive, ground, etc.

I just like to be careful. I have a literal pile of duet boards that are fried in one way or another because I carried on when I wasn't sure.

droftarts

@gnydick said in I'm confused about stepper motor voltage:

Like, what's Ve?

I think you are referring to where @deckingman said "... and the other side to the Duet heater -ve terminal ..."
"-ve" is negative. He means the negative terminal.

Ian

gnydick

@droftarts OMG, like i18n, but even slightly nerdier. Well done.

deckingman

@gnydick Yes, sorry. -ve is just shorthand for negative, and +ve is shorthand for positive. Unfortunately such shorthand terms are often used on circuit boards because there simply isn't room to fit the full length term in a legible font size. -ve could also be labelled "gnd" (short for "ground") and you might see vcc which generally means supply voltage (not sure what the "cc" part stands for), or 12v which means 12 volts. But being a nearly 70 year old, retired mechanical engineer, with little in the way of formal qualifications, I'm probably not the best person to advise you on electronics terminology. What I know is just what I've picked up over the years.

gnydick

@deckingman it's all perfectly reasonable. I'm the same, all self taught. I know the challenges.