Alternative to A3949 SOIC motor driver? (Newbie!)

Hi all,

I'm a 2nd year engineering student and have decided upon building RepRap Mendel as a project.

It's going to be a pretty steep learning curve for me as I have had no previous experience in electronics, and I am going to be building the PCBs from components rather than buying the ready-made boards. The problem I'm having is in finding a source for the (2x) A3949 motor drivers on the extruder controller.

Does anyone know of a source for these chips please? Or, failing that, could anyone tell me if there is an alternative to the A3949?

I see newer model numbers on the Allegro Microsystems manufacturers website but I have no idea at this stage whether any of them are compatible or not.

Can anyone advise a (clueless) newbie?

TIA

Andy

Edited 1 time(s). Last edit at 11/03/2010 12:06PM by suncoss.

Following up on my own question...

I've read elsewhere on the board that another way around this would be to make a fourth stepper driver board and direct output from the motherboard to this instead, leaving the A3939 on the extruder board redundant. Have I understood this correctly?

Does this solution require any changes to either the motherboard or the extruder board?

Is using a fourth stepper board the simplest solution?

Sorry for all the questions, and I am trying to answer them myself, but not having anything physically in front of me makes it all a bit harder to envisage properly!

Edited 1 time(s). Last edit at 11/03/2010 12:16PM by suncoss.

Digikey have loads
A3949

Hey Suncoss

I guess you are looking at building the Gen 3 electronics as listed here?

I purchased these from Makerbot, and am having problems with them. They do a lot of things that are not strictly required for reprap... such as the extruder controller is in fact designed to drive DC motors rather than stepper motors and has been hacked to work with stepper motors.

If I was at the start of my electronics path, I personally would go for the pololu scheme. Other alternative electronics schemes can be found here.

Perhaps you should direct your questions to the electronics forum here rather than in this forum. I think on UK people look here, and not that often either.

hope this helps. You have an interesting (and somewhat expensive) path ahead of you...

annodomini2 Wrote:
-------------------------------------------------------
> Digikey have loads
> A3949


Thanks annodomini2,

Is that compatible though as it has a very slightly different model number (A3949SLBTR-T) as opposed to the one listed in the bill of materials on RepRap.org (A3949SLB-T). Forgive my ignorance, but I don't know if there is any significant difference in the two chip models, even if they are part of the same family?

If they are compatible then great!

AgeingHippy Wrote:
-------------------------------------------------------
> Hey Suncoss
>
> I guess you are looking at building the Gen 3
> electronics as listed here?
>

Yep, that was what I was aiming at...

> I purchased these from Makerbot, and am having
> problems with them. They do a lot of things that
> are not strictly required for reprap... such as
> the extruder controller is in fact designed to
> drive DC motors rather than stepper motors and has
> been hacked to work with stepper motors.
>
> If I was at the start of my electronics path, I
> personally would go for the pololu scheme. Other
> alternative electronics schemes can be found
> here.
>

Oh...I hadn't seen that part of the wiki before. Thanks for that I'll give it a closer look.

Do you know if many of the components from Gen3 are transferable to the pololu scheme?

I ask as I have already paid out for the Gen3 components all bar the A3949 which I'm having problems locating (hence this thread).

> Perhaps you should direct your questions to the
> electronics forum here rather than in this forum.
> I think on UK people look here, and not that often
> either.
>
> hope this helps. You have an interesting (and
> somewhat expensive) path ahead of you...

Thanks again, I appreciate the advice

I've already gone over my budget, but I'm having fun and I'm going to learn a great deal from this project so I think it will all be worth it in the end.

Please tell me I'm right!

I use a standard stepper motor board for my extruder after blowing up my A3949.

You just need to change the extruder::sStep() function in the extruder.h file in the motherboard firmware to ouput a standard pulse rather than a level change. My code is shown below.

#define STD_STPR_DRV_EXTRUDER // use a normal stepper 
inline  void extruder::sStep()
{
   //buildCommand(STEP);
   //talker.sendPacketAndCheckAcknowledgement(my_name, commandBuffer); 
#ifdef STD_STPR_DRV_EXTRUDER
  //NAL: Send a standard step pulse to the driver board.
	digitalWrite(E_STEP_PIN, HIGH);
	delayMicrosecondsInterruptible(5);
	digitalWrite(E_STEP_PIN, LOW);
#else
   stp = !stp;
   if(stp)
     digitalWrite(E_STEP_PIN, 1);
   else
     digitalWrite(E_STEP_PIN, 0);
#endif     
     
}

Edited 1 time(s). Last edit at 11/03/2010 05:08PM by brokentoaster.

OK, thanks for that, I'll save a copy of those lines for future reference if I go down that route.

Decisions, decisions...

Thanks guys for your advice.

suncoss Wrote:
-------------------------------------------------------
> annodomini2 Wrote:
> --------------------------------------------------
> -----
> > Digikey have loads
> > A3949
>
>
> Thanks annodomini2,
>
> Is that compatible though as it has a very
> slightly different model number (A3949SLBTR-T) as
> opposed to the one listed in the bill of materials
> on RepRap.org (A3949SLB-T). Forgive my ignorance,
> but I don't know if there is any significant
> difference in the two chip models, even if they
> are part of the same family?
>
> If they are compatible then great!

Same part different supplied packaging, as I doubt you are using a pick and place machine, its not going to make any difference

Datasheet

Thanks again, thats solved my problem then.

Cheers

edit: actually I just realised the datasheet you linked to explains the naming code; I had looked at the datasheet in the original link you gave to the digi-key stock, but never picked up on that. So thats something else I've learnt - slow down and properly read the bloody info before running off and asking questions!

Edited 1 time(s). Last edit at 11/05/2010 06:43AM by suncoss.

Rule1: Always read the instructions (if they exist)

Rule2: Measure, Measure, Mesure again and for Good measure, measure again. (The other being Measure twice, cut once!)