Hi Peter, thanks for your reply, I guess I am looking for a yes it will work , or no it will not work kind of answer, can you elaborate on " it should work"
350W @ 24V is about 14A. 340oz-in or 2.4Nm motors take about 3.5A or so. Four of those is 14A. Wouldn't leave any power for drivers, etc! But all four motors are never gonna be maxed out 100% at all times. So... Should be fine. If in specific doubt, look at the current ratings of everything and add it all up. Get a bigger power supply if you're particularly concerned. But four 4A motors should run fine on the typical 350W 24V Mean Well.
Hi Rob, probably a silly question but I'm more of a woodworker than an electronics guy, will a higher watt power supply work with the Openbuilds Blackbox ? Can you recommend what wattage power supply would work even at all motors at peak? I don't mind spending a little more, thanks again, Mark.
The BlackBox only comes with 4A drivers, there's no point in going overboard on power availability because you'd already be close to maxing out the electronics anyway. Technically a higher wattage- say, I dunno, an LRS-600-24 or SE-600-24 or whatever their naming convention is these days- would work fine, you can't force current in that the motors aren't using, but it's gonna be running less than half capacity basically the entire time. 99.99% of people just get the 350W and have zero problems. The motors are never all going to be maxed out simultaneously, and if they are, you have much bigger problems than your power supply capacity. Or do what I did and get an RSP-1000-48 that you can stack four deep and current-share up to 84A. (Kidding, don't do that... If only because the BlackBox can only take up to 24V. Also I'm running five NEMA 24s and 34s with separate drivers, no BlackBox involved )
Note 4A @ coil voltage, not @24v. If its 3V coils for example: 3v *4A *2 coils = 24W per motor * 4 motors = 96w (add to that 20-50% for driver losses, heat, Inductive losses)
Drivers are still gonna chop it to hit an average current rating for thermal reasons regardless of voltage though, no? All it'll do is bounce around on the output caps of the PSU a bit, but should never actually overload it. But the drivers are presumably putting out the voltage being supplied to them, or else the linear-ish relationship between voltage supply and torque at a given RPM wouldn't exist. So there's still more power being used and dissipated through the motor coils somewhere. Microstepping is more of a concern current-wise with both coils more fully engaged, but I've still never seen it actually be an issue. Another one of those things that should be an FAQ, I'm sure.
Yes they do push the full supply voltage, but effectively, for planning purposes to all but the most nerdy of engineers, is more practical to calculate from the coil voltage rating (or rather resistance) Chopper drives use a high voltage to 'force' current into the motor. The motor never actually sees the higher voltage because it is 'chopped' as soon as internal feedback sensors detect that the voltage/current is rising. As such, we are both right and both wrong - most people dont dial in the Max rating anyway - overheating motors are no fun. So using that in the math (mine) adds some headroom for where I should account for Inductive losses too. - the average is closer to that sum, than yours, because the chopper doesnt keep the tap wide open - the math i use have been applied to practical use cases for a while without mishap (;
Got it. Makes sense, as an inductive system. Been a while since I needed to look at steppers in any great depth!
