You can go up to 36V, this will help you keep the moteors cool. The problem is the amps, you will need a power supply that can handle peaks up to ~ 3 times the nomal aperage of your steppers without giving in.
Which is nonsense I'm afraid. Its a 1.7A, 4 ohm motor, there is no voltage rating for these kinds of steppers.
the cnc sheild can handle 12 - 36V
can i go over 12 witout killing my steppers?
Yes, more voltage will give more top speed, not that you need that for an extruder I think.
Lets calculate the power the motor uses. 1.7 x 1.7 x 4.0 = 11.5W.
Three motors thus use 35W or so, not including the losses in the driver chips, which will be fairly
high at that current.
Something like a 50W supply would be the absolute minimum for 3 of these motors.
Note the A4988 CANNOT HANDLE 1.7A. Perhaps DRV8825 drivers would be better if you need the
full 1.7A, but they will still be struggling rather and need a fan to cool them.
If you don't use the full 1.7A, you can derate the supply power too.
Since they are currently working with the A4988 you must be running them at less then 1.7A already?
Rivindtre:
(still alitle confused about how it worked before with all 3 of them)
Maybe it did not. Grbl "can" deaktivate steppers if they are not stepping, which leads to interesting errors when the power supply ist to weak. Can't tell you how often I searched for an error with that configuration ...
1A? Better, yes, will it work, no. Get an old PC powersupply. ATX gives you 12V at ~ 50A for 20 € (new). That will work. (and you get 5V and 3.V and -12V etc. for "free")
i looked upp some of the specs for the motor driver the A4988, there it said "output drive capacity of up to 35 V and +/- 2 A."
and a few post further upp MarkT mentioned that "Note the A4988 CANNOT HANDLE 1.7A"
im very unknowledgeable when it comes to electric stuff so im sorry if im asking stupid questions.
(also if a 460mA is enugh to get 2 motors to move at a reliabel fast speed, why would i need such a jump in Amp to get the 3 to move? i dont need them to move very fast.)
again sorry if its a stupid question
No. Amperage is not Voltage. Your circut draws how many amps as it needs. If your power supply does not provide enough amps, then the voltage drops (that's what you observe right now).
The small Stepperdrivers as A4988 et al. are basicly toys. All have problems driving low resistance steppers at a low rates. But that's why they have the potentiometer on board: you can adjust the maximum current. Follow the instructions of your stepper driver on how to do that.
You do not have an oszilloscope, so you cannot observe what happens with your power source when driving 2 motors or 3 motors. If you want to dig deeper, there's a lot of literature out there. Or you simply use the biggest power supply you can get and be happy.
i looked upp some of the specs for the motor driver the A4988, there it said "output drive capacity of up to 35 V and +/- 2 A."
2A? Not on a tiny PCB it won't. It will melt! That 2A is with much more heatsinking, its the absolute maximum value, not a working rating anyway.
and a few post further upp MarkT mentioned that "Note the A4988 CANNOT HANDLE 1.7A"
im very unknowledgeable when it comes to electric stuff so im sorry if im asking stupid questions.
The A4988 datasheet gives the worst case on-resistances as 0.43 ohm + 0.43 ohm, so at 2A it will generate 3.5W of heat, too much for a tiny little PCB basically. The DRV8825 does better, worst case 0.32+0.32 ohm, so at 2A it generates 2.5W worst case. And at 1.7A it does 1.8W which is just managable.
(also if a 460mA is enugh to get 2 motors to move at a reliabel fast speed, why would i need such a jump in Amp to get the 3 to move? i dont need them to move very fast.)
again sorry if its a stupid question
Your supply does 12 x 0.46 = 5.5W, so its nowhere near what's needed for a single motor at 1.7A - clearly you are not using 1.7A or anything like it at the moment. A 12V 5A supply would be a choice capable of handling 3 motors running at their full rated current.
They might turn (which is a big improvement), do they have any torq? Can you stop them with your fingers easily? BTW, I would stay away from A4988. If they burn, they can take your arduino to their grave. DRV8825 are better decoupled, they do not need to be supplied with power form the arduino and have some extra resistors on the inputs.
And I would again suggest that you get a used PC ATX power supply. You can get it for free on the scrapyard and it's better than anything you can get on budget (and you will eleiminate most of your power supply problems in the first place).
