RAMPS 1.4 alternative stepper motor driver

I'm developing a conformal coating unit based on RepRap electronics and software. I already an extra RAMPS 1.4 and my host and firmware are heavily modified version of Printrun/Pronterface and Marlin, I'd like to stick with RAMPS 1.4. The stepper motors I have for my X,Z axes are rated 2.8A/phase (3VDC), and Pololu A4988 are clearly inadequate. Will RAMPS be able to handle a driver such as this: [forum.hobbycomponents.com]. As far as I can see, the inputs are the same if EN+, EN-, CW-, and CLK- are connected to ground. Will Marlin support this driver? or do I have to modify the firmware as well?

The 3V motors are limiting
Is this a true 3V motor or is the current rating at 3V
What type of motor is it?

I hope you don't need much power to drive your task
Low voltage --- high current
I think RAMPS designed for stepper motors 12 to 36 volts
The Pololu A4988 Black edition may help

The driver you posted is only 3A max ( voltage not given assume 10 to 24V)

I use Nema 17 and 23 with RAMPS with Pololu A4988 drivers at 12 and 24V to push around a 3d printer and CNC router
with no problem --- maybe motors get hot on long runs and holding current

Curious about those motors as well. Seems like it would just be easier overall to pick up 3 "normal" nema17 motors that operate with A4988 or DRV8825 polulu drivers that are out there. Normal meaning, matching the specs of the existing electronics. Does the machine you're designing require those specific motors? It's like this, spend $24 on 3 correct motors, or spend >$24 on replacement electronics...

... no, this 'low motor voltage' is normal for steppers - they are driven with max. current sensing and the 'over-voltage' is only good for fast changing the currents polarity.

I'm using 2A/2V steppers in my CNC-mill, with drivers that are specified with 70Volts and 6Amps max. - simply set the max. current for your motors, the efffective voltage is then simply a factor of Ohms law ...

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Viktor
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You've got it completely upside down. Though it doesn't seem to be done very often with regard to 3D printers, the torque needed to the job is calculated first, then the motor is selected to deliver that torque, then the electronics are matched to the motor.

3V (and less) steppers motors are quite normal and common even in 3D printing, and RAMPS would work poorly with 12V and higher motors. Steppers are typically driven by 8-20X their rated voltage. Driving them near their rated voltage will yield poor performance. Stepper motor current is rated based on temperature rise and designed torque. The voltage rating is just the winding resistance x the current and has nothing to do with driving the motor. When you set the current in the driver you're setting the average current as the instantaneous currents will normally be much higher than the rated current.

To answer the question, yes it would be possible to use these external drivers and you might have to invert one or more logic pins in Marlin.

this is the motor: [picpaste.com].

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the_digital_dentist
You've got it completely upside down. Though it doesn't seem to be done very often with regard to 3D printers, the torque needed to the job is calculated first, then the motor is selected to deliver that torque, then the electronics are matched to the motor.

3V (and less) steppers motors are quite normal and common even in 3D printing, and RAMPS would work poorly with 12V and higher motors. Steppers are typically driven by 8-20X their rated voltage. Driving them near their rated voltage will yield poor performance. Stepper motor current is rated based on temperature rise and designed torque. The voltage rating is just the winding resistance x the current and has nothing to do with driving the motor. When you set the current in the driver you're setting the average current as the instantaneous currents will normally be much higher than the rated current.

The main reason I want to use these motors, is their torque. I just wanted to make sure they'd be comparable with RAMPS, specially since I already few Arduino Megas and a couple of extra RAMPS. would rather not spend too much on microprocessor etc. However, I don't have any extra stepper motor drivers, and need to order a set. Just trying to find compatible ones.

Few month ago, for another project, I had to make my own custom shield (based on RAMPS). added relay switch boards for micro-step switching, among other small changes. (if anyone is interested, I can share pictures, designs etc.)

Are you aware, these are NEMA23 steppers with a different footprint than the common reprappers NEMA17?

You could also use drv8825 drivers, which fit on the stepstick port and deliver 2.5A max with cooling. Your steppers would loose only a small amount of torque then.
They also have 1/32 step capability, reducing the noise of the NEMA23 alot.
-Olaf

Then there is the common thought that microstepping reduces torque as well so...

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thetazzbot
Then there is the common thought that microstepping reduces torque as well so...

[OT]
We should start a stepper-weightlifting contest to verify this thesis.
-Olaf

I use a couple of these to drive the NEMA-23 X and Y axis motors in my printer with 32V power supplies. IRIC, they are set for 64:1 microstepping.

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o_lampe
Are you aware, these are NEMA23 steppers with a different footprint than the common reprappers NEMA17?

You could also use drv8825 drivers, which fit on the stepstick port and deliver 2.5A max with cooling. Your steppers would loose only a small amount of torque then.
They also have 1/32 step capability, reducing the noise of the NEMA23 alot.
-Olaf

Yes, I'm aware that they are Nema23 steppers. And my design is based on Nema 23 footprints.

regarding the drv8825 drivers, there is this slight limiting factor:

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The DRV8825 driver IC has a maximum current rating of 2.5 A per coil, but the current sense resistors further limit the maximum current to 2.2 A

These drivers are tempting to use, but I wonder how big of an impact it will have on the torque.

Edited 2 time(s). Last edit at 06/29/2015 09:55AM by _dreamer.

I'd worry less about the torque than the noise and vibration. 8825s are chopper drivers like the slightly lower current 4988s. DSP based drivers sense and modulate current around resonance and allow finer microstepping, both of which contribute to reduced noise and vibration.

You should not have any problems attaching the hobbycomponents drivers, you just need to locate the pins on the pololu socket on the ramps board, that has the 4 signals you need, a simple header with the wires soldered onto it would suffice. You may possibly have some issues with pulse width on the step and dir pulses, but i belive those are configurable on Marlin, as the there was a need to make them adjustable to support the drv8255 drivers, which in some cases needed slightly different timing.

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Tshawkins
You should not have any problems attaching the hobbycomponents drivers, you just need to locate the pins on the pololu socket on the ramps board, that has the 4 signals you need, a simple header with the wires soldered onto it would suffice. You may possibly have some issues with pulse width on the step and dir pulses, but i belive those are configurable on Marlin, as the there was a need to make them adjustable to support the drv8255 drivers, which in some cases needed slightly different timing.

that is what I ended up doing. And it works beautifully