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PSU rating

cnc CNC_Router laser power_supply PSU

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Hi everybody !

I'm building a little CNC router (and laser) for fun and learning more about CNC. Im currently using GRBL, arduino, TMC2100 and nema 17 for the hardware. To run all this, I bought a 12V 30 amps 360 watt PSU out of amazon, and I have a question about it ! My PSU has a potentiometer to set the desire voltage value, if my system draw about 10 amps, can I take the voltage up to about 20 volts ?

To recap my question: is the output rating voltage important to respect, or the wattage is more important ?

Thx for all the suggestions guy's. My hissing problem is now solve. I bought a CNC shield out of amazon and i put my TMC on it. All the sound is gone and I have plenty of torque ! Looks like I made a mistake in my initial wiring !!

Thx again !

If this is kind of power supply I got on my mind (cheap rectangular with lots of holes) then this potentiometer will allow you only finely tune voltage by 1-2 volts.

Speaking of hissing noise you experience with steppers, this might be obvious solution but did you try to lower current on TMC2100 potentiometer?

Yess, I have lower the vref, but the torq is then not enough for my usage. I also tried spreadcycle with the lower current but the hissing noise reappers since this mode is less quiet...I dont know what else to do...the hissing is worst with 3 drivers connected

If you have to run your stepper drivers on highest current in order to move your axis that means your motors don't have enough torque. Your axis should move smoothly and have plenty of power. In this case the best solution would be to gear down your stepper motors, easiest way to do it is to buy nema17 planetary gear:


What I forgot to tell you is that i need tu put the vref to 0.25V(0.2A) for the motor to stop hissing. normaly they run on 1.2V(0.85A). Thats why they dont have enough torque. The TMC's also heat pretty quickly if I ask them all to hold their position.. Im out of idea, and I just bought a GRBL shield to test other drivers and see if the shield could work with my TMC...

That's weird, they should work fine at 12v supply, there must be something else in your setup. TMC2100 gets hot very quickly have you got heatsinks attached to them?
I have lv8729 dirvers and they are very quiet, my printer is powered by desktop 12v PSU:


Yeah they have the heatsink attach to them ! Like you said, it might be my wiring setup...I'll have my mind set about that when i'll receive my grbl shield on monday. If everything is fine with the shield, then my wiring is wrong :P

Something to try for making the steppers quieter (and being gentler on the drive electronics) is increasing the inductance by connecting a coil in series with the motor windings. The drive relies on motor inductance to operate properly and if the motor is 'screaming' (can sound like hissing) one thing to change is the inductance.

(I used to build stepper driven stages for scientific equipment.)

I'll keep that in mind in my resolution process ! can you draw me a quick sketch of what you just described to me ?

I mean, it's really simple but here you go? If this doesn't make sense let me know where you're confused and I'll fill in details as you need them.

A possible inductor could be: https://www.digikey.com/product-detail/en/bourns-inc/PM3340-150M-RC/M8584CT-ND/775652

Or you could simply wind 20 or so turns of some reasonably heavy wire (say, 20AWG?) around a nail.

It also could be faulty stepper drivers, I received 2 faulty ones when I ordered my 3d printer board - motors were struggling to run and there was weird noise. Most drivers you see on ebay are chinese copies and quite often not working. Fortunately other 2 were working and I could troubleshoot it.

This is kinda OT, but to follow that up I will remind folks that TMC drivers should always be purchased from a legit retailer like Digikey... same prices as the ebayzon clonesium, but for legit parts.

In general, no you won't be able to run your power supply up to 20V.

There are some power supplies rated by the total wattage, but they are fairly specialized (like a Keysight benchtop supply).

If the power supply was capable of running at 20V you can be sure the manufacturer would put that on the label and raise the price accordingly.

If the PSU is rated for 12v then no, don't crank up the voltage. You have to keep in mind ohm's law. Your parts are probably rated for 12v so you should use 12v. If you go, say doubling the voltage, you quadruple the power. Power is a function of the voltage and current, P=VI.

P= U*I ... ;)

And above all you should not forget that the board logic probably does not run with 12V but with 5V/3.3V. That's why you usually have a so-called voltage divider on the board that "burns" the excess 7V in the true sense of the word! You can kill it if you go too high with the voltage!


To power the TMC i'm using the arduino(5v), but to power the motor (power goes into TMC and then to the motor like a normal stepper driver) im using my PSU, so no chance to burn the board :P

My real question is : Can I turn up my PSU voltage if I respect the wattage rating of the psu or I MUST respect the voltage that is written on the box ?

That's what I said wanker. If you want to get into it, it's an e.

Calling a linear regulator a voltage divider... I can tell you don't know what you're talking about.

The thing is that the TMC2100 use 12v to 36v to work and now when a wire only one stepper every thing is alright and quiet, but as soon as I plug the second one the motors start to make a hissing noise. I seen on other forum that the TMC2100 run better with higher voltage than 12v. That's why im wondering about pushing my PSU voltage up.

And from your formula, I understand this:

Pmax = VI ---> 360 = 12(V)30(I)

in my case im using less than 10 amps so :
200 = 20(V)*10(I)

and it would be less than the Pmax of 360.
Does it work that way ?

What is the rest of the hardware you're using? Like the limits on the spindle itself and the control board? I'd be worried about some wun hung-lo brand PSU not using decent(nichicon, rubycon, nippon chemi-con) polarized bulk decoupling smoothing caps rated high enough. If your output caps are only rated for 16v (a good bet) then you're taking away the overhead added for safety. Best case if you exceed the output cap rating would be shortened life. Worst case, they fail short and explode.

My PSU is a NEWSTYLE model S-360-12. I dont think its a chinesse brand. So what yout are saying is that i need to look to my output caps to see their rating and keep a security factor from there ?

the spindle is a dremel connected directly to the wall. and the laser (power by the PSU) is a 3.5 watt laser that take 12-36 volts

I've just look into my PSU and the output caps are 25V ! is that a good news for me ? :P can i cranck up the PSU to something like 20v ? :D

No you can't! Phisterbutt gave you the correct answer...


Been down this road many times designing my own curcuits... there is a lot more that goes in to proper cap specs than the voltage. Yes brand does count big time these days, but even with decent caps temperature and frequency of ripple can really serve to derate caps. In general output ripple caps are usually 2x the expected voltage, but add in temps and most cheap psus are way under spec with their caps. I wouldn't push a 25V cap over 12V if I were you... and if it was an off brand unknown cap even 12V may be pushing it.

No, but out of curiosity what's the brand on them? I'm guessing sam young. 25V is better than 16v but if they're some shit brand it's like ordering pop tarts at a steak house.

I keep forgetting to say to make sure that the 12v is around but not under 12v.

The brand is "yungli" is that a shit brand ? hahah ! :P

That is the epitome of Chinesium grade PSU. Yeah, that's exactly what I'm saying. That pot is meant for fine tune of the 12v, not meant to over drive the supply.

haaaaaa to bad then, i'll live with the hissing sound :(

Gotta do what ya gotta do... hissing, not printing, or spending big... one or the other.