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Topic: Power supply purchase, what do I need? (Read 617 times) previous topic - next topic

Zeuligan

Hi

I'm a total beginner, as my question will reveal, but I hope that is OK anyway.

I have started a project where I want to create my own cable cutter/stripper for small electronic wires (AWG17 and AWG15).

I bought 2xEasy Driver Shield stepping Stepper Motor Driver V44 A3967
2xNema17 stepper motors
The spec for the motors are
  • Rated current: 1,7A
  • Phase resistance (Ohm) 1.5
  • Phase inductance (mH) 2.8


What type of PSU should I get?

MarkT

Sounds like you don't need much speed for that task, so perhaps 12V supply will be fine.

The A3967's however are an issue with a 1.7A motors, since it can only handle an absolute
max of 0.7A or so and thus won't hack it at all.

DRV8825 is a better choice for higher current, probably set to 1.5A they would hold up
for that motor.

If you do the I-squared-R calculation for the motors you'll see each will dissipate around 4.5W,
so 9 in total at 1.7A (perhaps more like 7W if programmed at 1.5A).  Allow for losses in the
driver and the need to provide mechanical power as well as just heat the windings (!),
perhaps about 15 to 20W input power, so 1.25 to 1.8A at 12V  (or about half that for 24V
supply). 

It you do need high speed, 24V is better.  I'd therefore say 1.5 or 2A supply at 12V or
a 1.0 to 1.5A supply at 24V.

Rating supplies generously is a good thing, they run cooler and last longer, so don't be shy to
go for a somewhat higher current rating if the cost isn't dramatically different.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Zeuligan

#2
Nov 11, 2017, 12:55 am Last Edit: Nov 11, 2017, 01:10 am by Zeuligan
Sounds like you don't need much speed for that task, so perhaps 12V supply will be fine.

The A3967's however are an issue with a 1.7A motors, since it can only handle an absolute
max of 0.7A or so and thus won't hack it at all.

DRV8825 is a better choice for higher current, probably set to 1.5A they would hold up
for that motor.

If you do the I-squared-R calculation for the motors you'll see each will dissipate around 4.5W,
so 9 in total at 1.7A (perhaps more like 7W if programmed at 1.5A).  Allow for losses in the
driver and the need to provide mechanical power as well as just heat the windings (!),
perhaps about 15 to 20W input power, so 1.25 to 1.8A at 12V  (or about half that for 24V
supply). 

It you do need high speed, 24V is better.  I'd therefore say 1.5 or 2A supply at 12V or
a 1.0 to 1.5A supply at 24V.

Rating supplies generously is a good thing, they run cooler and last longer, so don't be shy to
go for a somewhat higher current rating if the cost isn't dramatically different.
Thx for the answer. So much to learn that I hardly know in what end to start.
Would A4988 be an OK choice or is the DRV8825 better?

To put it simpler, can I get a to powerful PSU? Lets say 36V or will that always down grade?
Basically do I need to match PSU exactly based on your calculation above or as long as I got more juice than needed, it will work? Not considering purchase aspect

Also, do I need to purchase anything else, while ordering that DRV8825 or A4988.
Like some other board than my Arduino? Found something called CNC Shield Board and someone referred to a ramp1.4

Zeuligan

I ordered a Original MeanWell Switching PSU LRS-350 36VDC 350W 36V 9.7A 30mm thickness
With a Keyestudio CNC kit for Arduino CNC Shield V3+UNO R3+ 4pcs DRV8825 driver /GRBL compatible

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