DIY CNC 2

So much advice already but a coupe of pointers including from some gecko docs I read years ago.
1. Doubling the motor voltage almost quadruples available torque
2. Any power supply for CNC can be overrated by about 40% so for 3 or 4 x 2 amp motors a 5 amp power supply is plenty
3, If a drive does not have a max temperature spec, be guided by the temperature the windings start to melt which is typically around 130 deg C but your motors are silent on that too. 80-100 deg C is fine

I always run 48 volts and sometimes as high as 90 volts but on a small machine I might consider 36 volts depending on manufacturers recommendations. 24 volts leaves too much available torque on the table.
I would prefer you to use seperate power supplies with the 7i96
Meanwell MDR-10-5 for logic (5v)
Meanwell MDR-60-24 for field power (24v) MDR-40-24 is Ok too.
Meanwell NDR-240-48 (48 volts) for motors but a LRS-350-48 (7 amps) might be cheaper and is a popular choice.
 

I like the idea of using a capacitor. I would just put that capacitor in parallel between the positive and negative terminals and add a bleeder resistor also in parallel also between the two terminals, correct? And this would protect my PSU and stepper drivers?

 

I always run 48 volts and sometimes as high as 90 volts but on a small machine I might consider 36 volts depending on manufacturers recommendations. 24 volts leaves too much available torque on the table.
I would prefer you to use seperate power supplies with the 7i96
Meanwell MDR-10-5 for logic (5v)
Meanwell MDR-60-24 for field power (24v) MDR-40-24 is Ok too.
Meanwell NDR-240-48 (48 volts) for motors but a LRS-350-48 (7 amps) might be cheaper and is a popular choice.

I can spend that much but I feel like I'm already splurging with this card. I also feel that the NDR-240-48 might be tool little current. Just curious but why should I swap to a separate power supply for the 7i96.

I can't see where you mentioned how many drives you are using. For CNC all motors are almost never running in unison and requiring full current is rarely needed. 3 motors at 2 amps = 6 amps. 6/1.4 = 4.3 amp power supply required.As I said a 7 amp power supply is probably cheaper.

If you follow my advice and run a higher voltage power supply for motors, you need a seperate 24 volt power supply for field power. Whilst you could use a buck power supply for 5 volt logic but the power supply I suggested is only about $20. Given the number of issues I've seen where people have tried to use 5v plugpacks or phone chargers for mesa cards, the extra $10 is a small price to pay for reliability.
 

Certainly use separate PSU for motor drives vs other electronics. I had overlooked that detail. Most motor drives produce lots of electrical noise which will tend to interfere with the other electronics.

Yes, if you use a capacitor, connect direct to PSU output. A lot of these capacitors have only the -- terminal marked. Make sure you do not connect it backwards. I did by mistake one day, electrolytic capacitors burst when powered backwards. Connect capacitor+ to PSU+ and capacitor-- to PSU--

With your 20A PSU I would not bother, it already contains enough capacitors. Quality Delta and Mean Well PSUs 7A will certainly work. Cheap off-brand knockoffs 7A might work but be plenty small as they are built so light.

Given the number of issues I've seen where people have tried to use 5v plugpacks or phone chargers for mesa cards, the extra $10 is a small price to pay for reliability.

I will probably get that device then.

I can't see where you mentioned how many drives you are using.

I'm using three drives

If you follow my advice and run a higher voltage power supply for motors, you need a seperate 24 volt power supply for field power.

Is it really that significant? Using a 48V PSU vs a 24V psu. Unrelated, but I feel like you may be sponsored by meanwell.

Noted, I kind of like rodw's idea with the separate power supplies.

Logthor wrote:

Is it really that significant? Using a 48V PSU vs a 24V psu. Unrelated, but I feel like you may be sponsored by meanwell.


 

No, I can second most of rodw's numbers. I nearly said the same thing earlier and didn't bother, as your original list looked like a good start.

You will get much better speed from your steppers if you power the drives with 48V

The greatest improvement will be that the fast moves between cuts will be faster.