input on a new driver board
February 22, 2011 11:13PM
I'm designing a driver board based around 4 A4983's (same driver as Pololu) and was wondering if anyone had an opinion as to what features should be included. I already am using as much ground plane/heat-sink as possible, and left a lot of room around the chips so a single 4" x 0.75" heat-sink could be placed over all 4 chips.

Do people usually play with the different micro stepping settings or just leave them at 16x, 8x, etc? Same with the sleep/enable.

Also, would it be nice to have a dip switch selectable current limit for the entire board, or is it better to just leave the existing pot-for-each-chip implementation?

Edited 1 time(s). Last edit at 02/28/2011 11:55PM by Andrew Diehl.
Re: New driver board "want" list
February 23, 2011 02:29AM
I like the trimpot, a more common cheaper model might be beter though.

Also I want the molex plug back as I am using a PC power supply tongue sticking out smiley




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Re: New driver board "want" list
February 23, 2011 04:54AM
Quote

Do people usually play with the different micro stepping settings or just leave them at 16x, 8x, etc? Same with the sleep/enable.

1/16 microstepping is a bit much for threaded rod axes like the Z carriage so yes, people expect to change this. One point of confusion is the different pullup/pulldown handling of MS1/MS2/MS3. All three should be equal and work with the connector left open.

Never seen a set of electronics enabling Sleep, but Enable is often used as a measure to bring down the waste of energy between prints. Others switch off the entire PSU, so be prepared for 5V and 12V to suddenly appear or disappear.

Having the current adjustable is mandatory, as many different motors are used.

The Pololu breakout board pretty much satisfies the demands of RepRap machines, so the room for impovement is probably limited to removing the few excess components.


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Re: New driver board "want" list
February 23, 2011 08:01AM
I heard [www.allegromicro.com] can run slightly smoother.
The a4983 current is rather low which makes it to have fewer applicabilities in my eyes.

About a3984, never actually tried one, but i think i would prefer it to a4983, if it would be a fresh start.
But again, that may be just me.

Edited 1 time(s). Last edit at 02/23/2011 08:04AM by NoobMan.
VDX
Re: New driver board "want" list
February 23, 2011 08:41AM
... be carefully with max. current!

Quote

2 A peak output current
The 2 A rating is 0.5 A above most competitors. Additional safety margin for high-reliability designs.

The '2Amps' is the peak current value, what's normally not meant for constant operation and only available with proper cooling!

My experience is, that you have a continuous current (with cooler) and you can have around 30% more for a short time, what's called 'peak current' - my 3Amps drivers can drive until 4Amps peak, but only for some seconds, then they have to cool down again ...

So my estimation for continuous current with the (cooled) chip is something below 1.6 Amps ...

Edited 1 time(s). Last edit at 02/23/2011 08:42AM by VDX.


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Re: New driver board "want" list
February 23, 2011 09:32AM
Check this out [forums.reprap.org]

Alot of ppls way smarter than me, which i respect, posted there so i just do like i usually do: save my brain the usual painful thinking process and take what is said there for granted. I have a bunch of 12 pololu boards but havent yet tried any, i plan to use them with G7 with a huxley and nema16 or 11 motors. Would get a better impression then than i do have now. Atm i am much more happy with some a3977 drivers i did myself and heatsinking them properly and they dont even break a sweat and are always much cooler than i would of expected (i think i could set vref up to actual 2A and they would work ok, but i dont need that much). Although the a3977 is rated like 2.5A and the a4983 says its 2A, i think the actual difference is very much more bigger than that. At least what i think.

The a3984 maybe could be somewhere in between, and if i am not mistaking it is somewhat newer than a3977 (which is rather old), so 3984 may have some newer features. Just trying to justify why i pointed at that instead, and again, its only my opinion -and not afraid to say i had a lot of bad ones over time hehe smileys with beer.
Re: New driver board "want" list
February 23, 2011 07:04PM
Note that the a4984 doesn't provide 1/8th stepping.

While this shouldn't be an issue, it IS worth noting.
Re: New driver board "want" list
February 27, 2011 04:49PM
I got a proto up and running with the 4983 chip. Runs very nicely with my 30oz-in nema 17 motors without any forced cooling (on a single sided board with no ground plane). I'm breaking out the enable on all 4 chips and tying them together so if someone wants they can play with it.

I'm adding a 100k pull down on ms1 and am debating the best way to allow changing the stepping settings. I'm 50/50 split between a smt dip switch or solder jumper pads. I'm going to try and use both footprints so I can add the dip if I dislike the solder jumper, but if i can't make it work which would be preferred (cheap or easy?)

Does anybody use steppers with a shield on the cable?

I'd really like to use smt connectors for the steppers, optos, and maybe even power, since it will virtually eliminate any hand soldering required. Any suggestions for smt connectors which will be compatible with the current polarized molex?

Thanks!
Re: New driver board "want" list
February 27, 2011 11:59PM
Please consider designing an A4983-based stepper controller board to replace the Gen 3 stepper controller board. Most of the current designs rely on the Pololu carrier boards which seem to always be in short supply. In addition, there's a significant saving to be had by using the chips instead of the carrier boards even though it might make it harder to replace the chip if it goes bad. For this reason, it would be better if there are separate boards for each axis. Also, it probably makes sense to replace the X, Y and extruder stepper controllers with the A4983, leave the Z axis on the old Gen 3 stepper controllers.

Edited 1 time(s). Last edit at 02/28/2011 12:01AM by brnrd.
Re: New driver board "want" list
February 28, 2011 01:37AM
from allegro,s web site that talks about each stepper. A3984 does not support 1/8 but supports 1/16
step. description of the chip sets discuses on this page is below.
------------------
Leave the enable lines attached, that may be a good idea. there are many firmwares that enable and disable them, and z axis and e don't need to be enabled at the same time usually. Leaving those lines connected would improve power efficiency.

It would also be nice if there was a method for selecting voltage reference to motors as well as current with analog micro potentiometers.

you get more speed out of higher voltage. other than starting times, current draw of a stepper motor is really low. so allow the highest voltages to be handled by your 5v regulator. (for the 5v input logic power to the DMOS)
also external diode protection is a must. the led lights are nice to see on the h-bridge, and good for troubleshooting.




----------------
The A4984 is a complete micro stepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and eighth-step modes. Step modes are selectable by MSx logic inputs. It has an output drive capacity of up to 35 V and ±2 A. The A4984 includes a fixed off-time current regulator which has the ability to operate in Slow or Mixed decay modes.


The A4983 is a complete micro stepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, eighth, and sixteenth-step modes, with an output drive capacity of up to 35 V and ±2 A. The A4983 includes a fixed off-time current regulator which has the ability to operate in Slow or Mixed decay modes.

The A3984 is a complete micro stepping motor driver with built-in translator for easy operation. It is designed to operate bipolar stepper motors in full-, half-, quarter-, and sixteenth-step modes, with an output drive capacity of up to 35 V and ±2 A. The A3984 includes a fixed off-time current regulator which has the ability to operate in Slow or Mixed decay modes.
Re: New driver board "want" list
February 28, 2011 01:27PM
One more question:

Male or Female .1" headers for step, dir, and enable?
Re: New driver board "want" list
March 02, 2011 01:31AM
The gen3 documentation pinout setup is here. [reprap.org]. that pinout is what most people are using. I think those are 10pin mail headers on the board. Possible reasons for the pinout are for noise in wires, and power requirements.

Use what people are familiar with, make is so all they really need to do is plug it in, and you are sure to win customers.

I am just guessing here, but I assume about 80% of the population here uses some form of gen 3 device. And every week, someone smokes a stepper driver. Just the reason to buy a better one, possibly from you.
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