DRV8825 vs A4988. Star Wars - Imperial March...

(Michaël Memeteau) #1

DRV8825 vs A4988. Star Wars - Imperial March…
@Eclsnowman , What’s your favorite?#qr #drv8825 #a4988

(Eric Lien) #2

@Michael_Memeteau ​ you design such elagant parts with the K.I.S.S. method at its heart. That is one sharp looking printer. Great work.

(Michaël Memeteau) #3


(Eric Lien) #4

I feel the better sound is likely off the A4988. But I like the grunt my dvr8825 drivers have for actual printing. That being said I also really like these drivers http://www.panucatt.com/mobile/Product.aspx?ProductCode=SD6128

(Ryan Carlyle) #5

SD6128s are brilliant. Unlike 8825s, they can handle any motor/PSU combo you can come up with and won’t cause low-speed ripples.

(Daniel Kruger) #6

Is that heavy fishing line?

(Mauro Manco) #7

Daniel on qr we use 2mm dyneema cord , generally not for fishing (not arrive to this size) for other sports like kite,alpinism ecc . on printed pulley or directly on 5x5 coupuling.

(Mauro Manco) #8

Ops Michael drv for printing a4988 for sound…

(Michaël Memeteau) #9

@Daniel_Kruger @Mauro_Manco Those are actually 1 mm Dyneema (Same as Spectra but different commercial name). They are rated for 130 kg and don’t stretch, but since the spindle is totally parametric, putting any other combination (different dyneema diameter or different course) is a snap with onshape. Try it for yourself:

(Michaël Memeteau) #10

@Ryan_Carlyle Thanks for the tip, Ryan… I didn’t start printing and this was already a concern.

(Michaël Memeteau) #11

@Ryan_Carlyle @Eclsnowman Do you know of any tip that could trick the 8825 into a quieter mode (slow decay or something?). Also, I’m not sure the SD6128 are compatible with AZSMZ Mini. For some reason, the vendor only recommend either the 8825 or A4988.

(Ryan Carlyle) #12

@Michael_Memeteau is your noise concern motor humming when they move, or hissing noises when the motors are stationary? The motion humming is helped by lower drive current, finer microstepping and using good stepper dampers (eg http://www.ultibots.com/nema-17-damper-astrosyn-my17rmdamp/). The hissing comes from the awful fixed-frequency chopping algorithm the 8825 uses, and the fact that it’s not intended for driving the low-inductance motors we use for 3DP. Dropping PSU voltage, changing motors, or switched decay mode MAY help. But you may also screw up performance… Slow decay is basically garbage with the 8825.

The SD6128 will work with any board that uses a standard Pololu style socket. It’s quite new though, most people haven’t heard of it.

(Michaël Memeteau) #13

Ok… Actually it’s more like @Eclsnowman is saying. It’s more like grunt, there’s something harsh to hit and inducting some nasty vibrations, especially at low speed.
I was able to get rid of the audible part of the hissing, but my cats are still about it.
I already have some flexifil/ninjaflex thingy between the stepper and the structure. That helps a little for sure. Not like the original stuff, but also not that expensive anyway.
I may play also with the diameter of the spindle, but I’m already on the low side of it (small diameter).
I think I’ll order the SD6128 (can only find them from the US).
Also great work at https://github.com/rcarlyle/StepperSim

(Michaël Memeteau) #14

… and I’m already on quite low on current (Each axis has a 2 stepper, so that’s 1.2A divided by two). In theory, would I gain something connecting them in serie?

(Ryan Carlyle) #15

If you put the motors in series, that would help with the low speed / low inductance issues for the 8825. Would be a good thing to try. No promises though. Should also reduce your top speed a lot, so do some good testing.

I am not positive about the pinout being compatible with your board, but the RAPS128 is available in Europe and uses the same driver chip as the SD6128. It’s designed for RADDS and is quite popular in Germany.

(Michaël Memeteau) #16

@Ryan_Carlyle I’ll try and let you know. Thanks for the valuable advices.

(Michaël Memeteau) #17

@Ryan_Carlyle I followed your advice and bought the SD6128 (from Panucatt) but I think that I may have fried them by misinterpreting the documentation. Is there a simple way to tell (just have a multimeter). I was also thinking that my board wasn’t supporting the 1/128 microstep, so I unweld the MS1 pin to get back to a more comfortable 1/32 as the DRV8825 were configured. Basically when plugged correctly, the stepper just doesn’t move nor is energized. Any hint?

(Ryan Carlyle) #18

@Michael_Memeteau should be a drop-fit replacement for 8825s. What board are you using? I wouldn’t go over 1/32 for 8bit boards or 1/64 for 32bit boards. (That’s for typical 16-20tooth GT2 size pulleys.)

First thing to check, are you getting ground on ground pins, logic voltage to the VCC and EN pins and PSU voltage to the VMOT pin?

(Ryan Carlyle) #19

And what voltage do you have from the vref check point (little hole next to the wiper and pins) to ground? Should be vref*2=amps.

(Michaël Memeteau) #20

The board is an AZSMZ Mini (32 bits). I’ll check the values you’re suggesting and report back. Thanks!