Stepper drivers

Hi everyone,

I’m thinking in build 3d Printer, but I don’t have money to buy every piece of hardware.
I already had Bridge H L298N to run my motors.

I want to know if it’s possible run the stepper motors with it or I need to buy the RAMP ?

RAMP = Arduino Shield to 3d printers (http://hobbyking.com/hobbyking/store/__46895__3D_Printer_RAMPS_1_4_Control_Board_Kingduino_Mega_Shield.html)

Independently the answer, what you guys think ? I should buy the RAMP ?

tks
Brunno

A requirement I'd say, you need chopper drivers for snappy high-torque performance from your stepper motors. You also get software compatibility out of the box, so to speak.

An L298 cannot give you chopper drive (current control) that's needed for low- impedance high performance stepper motors.

Still you can try using a high impedance motor and see how fast it goes - depends what top speed you need.

ok, I will try it, but maybe I'll need more control above my current, because 3D Printer are to sensitive to the speed. To do a good printing I'll need to control the speed at the minimum

thank you

brunnot: ok, I will try it, but maybe I'll need more control above my current, because 3D Printer are to sensitive to the speed. To do a good printing I'll need to control the speed at the minimum

thank you

I don't understand what you are trying to say here. Do you understand the principle of stepper motor systems?

Yes, I understood that the stepper motor need more accurate current that L298 can't give

That's it ?

No that's not it.

Steppers need active current control to perform at speed. Passive control (by using a supply voltage matched to the winding resistance) will work at stationary and low speeds just fine, but fails as the speed increases.

With a chopper drive circuit the winding current can be kept at the same value as the motor speed increases (and the various back-EMF's increase). With passive driver the back-EMFs eat into the supply voltage and reduce the current.

You have both motor back-EMF from the rotation (constant, speed dependent) and inductive back-EMF (transient on every step).

A chopper driver would typically feed, say 1.7A into a 2 ohm motor from a supply of anything from 24V to 120V. The chopper acts as a buck-regulator using the motor winding as the inductance, thus being very power efficient, yet allowing the back EMF to be very large (as it is at high speeds).

By itself, the L298 can't do what you want to do (well - it could - more on that in a bit). What you need to use in addition to the L298 is it's sister chip - the L297:

http://www.farnell.com/datasheets/1696835.pdf

It provides the current control via a chopper driver. As far as using the L298 by itself? Well - in theory you could monitor the current with a couple of the Arduino's analog input pins (additional circuitry in this stage will be needed - see the block diagram of the L297 in the datasheet), then vary the PWM output to the L298 controlling the windings - in short, you would be programmatically emulating the L297; there's enough information in the datasheet to get you started.

The upside (what bit there is) is that you could probably add modes and functions that the L297 doesn't offer.

All that said - there are more efficient drivers/boards available, based on MOSFET drivers. Look into what Pololu and similar companies offer.

Also - realize that RAMPS for the most part is a system (consisting of both hardware and software) meant for easily and in a standardized manner interfacing a particular set of stepper drivers to the Arduino Mega (along with other inputs and outputs, and other hardware designed for CNC, 3D printing in particular). The hardware acts as a carrier board for these drivers; one particular driver used is:

https://www.pololu.com/product/1182

There are others as well with the same footprint as that carrier board, but with other actual stepper driver ICs.

The Thread stepper motor basics may be helpful.

Use a specialized stepper motor driver rather than a h-bridge.

...R