MakerBot V3.0 Stepper Controller

Has anyone else spotted this at [www.thingiverse.com] ?

I'd personally greatly prefer the smaller connectors for end-stops, and the 1/8th stepping driver chip sounds excellent.

I'd also probably replace the motor connector with screw terminals, although a crimp connector might be more mechanically sound.

would be nice to see this up on the wiki somewhere too

Never noticed that before, though I don't like how they have decided against continual use of the ethernet connector, much like how in the Mendel assembly they have the USB cable going to the motherboard crossing over the same lines that control stepper motors, which is a big no no.

Personally, when my printer is up and running, I have to redesign these boards to be better EMC and kitable, using more ethernet connectors

the motherboard<->stepper channel in gen3 doesn't use rj45 which seems odd to me, maybe because 4 twisted pairs don't cut it?

However, I'm more interested in the chip with built-in 1/8th stepping and quieter current control than cabling concerns.

Zach Smith replied to my enquiry, saying:
"Good question. We're still ironing out the last few bugs on that
board (gotta tweak the r/c circuit for best performance) Once we get
that, we'll be releasing the boards and they will become the new
standard.

I'm terrible at estimating time, but it will probably be 1-2 months
before we launch them."

I don't think their current design is thoroughly thought out, lots of parts, smaller pitch SMD makes for serious problems for the novice.
Still no sign of better EMC.
Will you really use 1/8 or even 1/4 stepping?

I shall not be buying it, id rather use an L297/L298 combo, as its simpler and more than adequate, or the easyStep which local supplier [mindkits.co.nz] sells now.

apparently the easystep only goes to 750mA, which from what I've read doesn't quite cut it. However, a similar module with the A3977 (rated 2.5A) would be perfect

Not true, i've observed Mendel(ssohn) operating with said drivers, and it was running just fine, with less than 1/3 the footprint of the MakerBot boards.

I hope that Vik will have his going fully at the next Arduino Group next month, to see if he is still using these boards

Hmm... that Allegro A3977 chip is gonna cost the community quite a bit...
8.31$ Single unit price at digikey. The chip i wanted to use with pretty much the same specifications and functionality (Ti DRV8811) is listed for 4.05$. Okay, it's not available in a PLCC package, but i still perfer to go the Ti road.

And i have to agree with Grogyan about the EMC too. It's only a couple of footprints more that need to go on this board, so people who do have problems can add a varistor or capacitor to the critical signals and get rid of any EMC problems. Well, maybe next time...

(BTW: My own project with my Stepper Driver Board based on the DRV8811 was put on ice for some time because i just did not have as much time to work on it as i expected, but i will get there sooner or later and will keep you posted as soon as i make any significant progress)

looks like the DRV8811 and the A3977 TSSOP are pin-compatible with one another, which is awesome for both of us because I'm currently redesigning the v3 stepper board to accomodate the smaller and cheaper TSSOP package

Yes they look compatible but the TI part works at higher voltage and also has higher RDSon as a consequence.

It is hard to get the heat out of those TSSOP packages without 2oz copper and a 4 layer board, so higher RDS is not good if you want the full 2.5A. I note that the RapMan electronics needs a fan.

Edited 1 time(s). Last edit at 11/05/2009 10:30AM by nophead.

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[www.hydraraptor.blogspot.com]

ah, good point about the Rdson.. DRV8811 is about 30% higher

ever tried cutting a hole in the board and strapping a heatsink directly to the chip's thermal pad? or mounting the chip upside down for similar purpose?

No but I think Ian Adkins has done that.

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[www.hydraraptor.blogspot.com]

Is there any reason an L298 couldn't be combined with an ATTiny13 instead of a L297? It seems like this would be cheaper than these custom chips at $5+. As a bonus, with a firmware change the board could drive a DC motor or a heater and a fan.

I doubt the ATTiny13 could do the closed loop chopping and micro stepping.

The L298 is ancient technology. Out of the 12V you give it it wastes about 4V so needs a big heatsink and reduces the maximum speed you can get from 12V. When you add the price of the heatsink and extra PCB area it is more expensive.

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[www.hydraraptor.blogspot.com]

The L298/297 combo is a very reliable stepper driver and been in use for a long time, the reason for the move to a one chip solution is that along with less power wastage, smaller total footprint, that you will have a better choice of possible drive resolutions, currently the L297 only goes down to half step

Hello,

I am developing a stepper motor controller board based on DRV8811 for a open source project. Few images of the prototype are here:

[www.gadgetfactory.net]

The board is very small, 1.6x2.5 inches in double layer, fabricated with 1oz laminate. It has most settings and controls available. The board is designed with a conservative DRC, 8mil track width and 0.6mm drill size.

The results are encouraging for running a 24V/2A motor at 300 rpm at 1.5A, the upper part of the board get to 40°C (104°F) (apparently due to unequal distribution of thermal area), through the chip itself stays around 33°C (92°F), when measured at bottom side of PCB on the thermal pad. The lower part of the board with much larger area available stays at ambient of 28°C (83°F) in India.

I have increased the board length to 3 inches to equalize the thermal area, added a few more thermal vias, updated some footprint issues and will be making this board with 2oz laminate.

I reckon if the board does well with DRV8811, it should do much better with A3979 with almost half the Rds(on).

Will keep you guys of progress.

Girish

I'd be interested in seeing how you get on in comparison to A3979/A3977, as they appear to be less than half the price of the allegro parts here in the uk

Yes TI parts are ridiculously cheaper than Allegro parts, but are pin replacements. I have used both A3977 (in PLCC package) and A3979, but not in the same environment/board. I blew a lot of A3977s so I was a bit apprehensive with A3979, especially with its tiny package, but it worked perfectly on first try and doesn't heat up at all.

As for DRV8811, given enough copper area and proper layout + PCB (that A3979 requires as well) I don't think it would be much of a problem. In fact we are planning to switch to DRV8811s on the above mentioned board, if the tests turn out good. Will know for sure in a couple of weeks.

Regardless, I think DRV8811 could be derated to 1.5A or 2A for regular use, since it is cheaper than similarly rated Allegro parts, say A3982. Besides, its pin compatibility with A3979 makes it good choice since we can always switch to A3979 on the same board if needed.

Do TI have an A4983 replacement?

I don't think they have a replacement for A4983, maybe they will make one if it becomes popular. It would be fun to lay a board for QFN A4983 though.

I personally like the extra resolution this device potentially offers, with 1/4, 1/8, and 1/16 stepping modes.

I like the potentially microstepping feature although I think most people do not really need them (currently).

The thing I dislike most about v2.3 is the motor side connector with its really odd 0.156'' pitch (3.96mm). Maybe it would be better to use a e.g. 5.08mm pitch connector.

Another thing is that I would think about getting the Vref pin somehow hooked up to the uC, so one could control the maximum current by software.

Anyway, thanks for the work on all the boards and the various versions thereof.

microstepping would be awesome for the v2 extruder which needs high torque at low(ish) speeds