Was about to get a toy- then I did some research...

[NeoMorph]

I keep meaning to ask, do you guys use surge protection or, better yet , run it through a UPS to clean the mains transients from glitching out the machine and computer. I’m wondering if a domestic surge protection device would freak out. I seem to have this memory of a computer with a beast of a psu that kept freaking out because of the surge protector (think it was 1200w psu because of all the extra stuff he was using including a crazy raid array and loads of RGB). Once he ditched the surge protection the machine worked fine.

That’s why I’m thinking a decent UPS would at least let you shut down safely. Or is my OCD going overboard again?

[Neale]

The fact that the drives are rated at "20V-70V" AC in is a pretty clear indication that they are very tolerant of input voltage variations. The only thing that really worries them is input overvoltage, which is why Jazz has suggested aiming at about 10% under the nominal maximum to give a bit of headroom for the odd spike, mains surge, etc. There is no point in cleaning up the raw AC input to the drives. These devices are power switching to motors, not audio amplifiers! I hung a 'scope off the DC supply to my drivers some time ago and saw something like a 10V 100Hz ripple across the smoothing caps and the drivers clearly weren't worried about that - they've been working for a few years now quite happily. There are things that need close attention, like good earthing techniques, keeping noise-producing high power cables away from low-level sensitive feeds to inputs, but the basic supply to the drivers can be pretty crude by comparison. In fact, a simple linear power supply will beat the pants off a switched-mode supply when it comes to feeding stepper drivers as you have to drastically over-spec the SMPS to cope with the odd peak load which causes it to go into shutdown or some other protective mode where the linear supply just dips a bit and carries on.

[JAZZCNC]

but the basic supply to the drivers can be pretty crude by comparison. In fact, a simple linear power supply will beat the pants off a switched-mode supply when it comes to feeding stepper drivers as you have to drastically over-spec the SMPS to cope with the odd peak load which causes it to go into shutdown or some other protective mode where the linear supply just dips a bit and carries on.

Neale is 100% spot on and using an SMPS is asking for trouble because at some point it will bite you when it goes into protection mode. KISS works for CNC no need for over complicating the job with Surge protectors or UPS, DHL, FedEx or any other courier service...

Now back to these drives and the Question of AC or DC. I've used these drives with both AC & DC and in terms of performance, I've seen no differences.
However, I've never run them on machines working in harsh conditions regards power fluctuations, etc but I suspect that if the mains supply was prone to fluctuations or was a little dirty then using a DC supply would be less stressful on the drives due to larger Caps being more capable of smoothing out the power than the little caps that will be used on the individual drives.

Now I'm not into electronics so I don't know if when using a DC supply the drives still use their onboard Caps as extra smoothing.? . . my gut says they probably do.!

But that said I would always go with the simple approach if normal conditions so AC is easier and cheaper. The machine doesn't care if you run it on Everyready battery's so long as it gets a nice supply of power when it asks for it.

[Kitwn]

Now I'm not into electronics so I don't know if when using a DC supply the drives still use their onboard Caps as extra smoothing.? . . my gut says they probably do.!

If they use the same input connections for DC as AC as I assume they do then the rectifier and capacitors must still be in the circuit.

One other thing to consider: If you add an additional rectifier and capacitors to make a DC supply for an AC driver you will also increase the inrush current to the transformer and increase the risk of trips. Adding more capacitance for the sake of it to any DC supply (making Neale's audio amp PSU instead of a motor driver one) will have the same effect.

[NeoMorph]

If they use the same input connections for DC as AC as I assume they do then the rectifier and capacitors must still be in the circuit.

One other thing to consider: If you add an additional rectifier and capacitors to make a DC supply for an AC driver you will also increase the inrush current to the transformer and increase the risk of trips. Adding more capacitance for the sake of it to any DC supply (making Neale's audio amp PSU instead of a motor driver one) will have the same effect.

Yup. My brain was in full “doped up on morphine mode”... which is why I did a facepalm. It’s the reason I had to quit work. Not asking for sympathy, just stating the way things are. I seriously do not know this tech, BUT I WANT TO LEARN. It’s better to ask questions and act a fool than profess to be an expert and tell people incorrect info because “Well it works for me so must be okay”. A lot of my expertise is 20 years out of date and worked with super delicate security systems that required strong, stable power sources to detect intrusions. These days you could build the same thing for lest than 50p with tech from Asia.

But I love making things which is why I got into CNC in the first place. Anyhoo... I’m going to shut up until I can reduce my meds come spring.

[NeoMorph]

From what Neale said made me do a facepalm... not at him, at me. Of course the driver will clean it up. I’m a moron.


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[Kitwn]

Don't fret mate!
My radio/TV background doesn't allow for much ripple on a DC power supply so I was expecting to see huge quantities of expensive smoothing capacitors on a linear supply of the sizes discussed here. For this application you don't need that much.

I'm not brainy enough to use Faraday's Law to work out the inrush for a given transformer, but I suspect you need a pretty chunky lump of iron for that to be the only significant contributor to the overall inrush.

[NeoMorph]

Don't fret mate!
My radio/TV background doesn't allow for much ripple on a DC power supply so I was expecting to see huge quantities of expensive smoothing capacitors on a linear supply of the sizes discussed here. For this application you don't need that much.

I'm not brainy enough to use Faraday's Law to work out the inrush for a given transformer, but I suspect you need a pretty chunky lump of iron for that to be the only significant contributor to the overall inrush.

Hah... try doing math when your head is on the equivalent of 10 pints of lager. I read some of the posts here and go, “Errr... what the heck? The drives can take AC direct from the transformer... that ripple is going to be awful!”, without thinking it through that the drive itself will do the cleaning.

This is the problem with someone who knows a little bit of knowledge and thinking they know what to do (that’s me btw). Unfortunately, microelectronics which is VERY pick about power stability and a CNC drive that is going to take 60v from an AC transformer is two very different things.

Unfortunately I won’t be able to get my kit for at least a month apparently... nobody appears to be working at the factory/distributors in China. They are talking 2 weeks to even start back up again and maybe longer.

[Kitwn]

The rated current of a stepper motor is the maximum permitted continuous current in each winding. This will flow in the windings when supplied at the rated fixed voltage, something you will never do in practice for the reasons Dean has outlined above.

[Boyan Silyavski]

Best would be if Spindle centre /the bit/ does not go further than than carriage, machine looked from side . But If not possible its not a problem . If square linear rail is used. Though for metal work i say better not, for a perfect finish i mean.

Red line shows the ideal, blue line the normal. I would say 250-260mm span for me is the minimum of the gantry legs/ bearings