I need help Correctly setting trim pots on pololus. I have some crazy stuff happening to my prints. I have stepping up to left (not a ramp but like a step is off). Other times it goes crazy and randomly places the zozzle somewhere for a layer. I have played with the pololu trim pots. I cant seem to get it right randomly. If I turn up too much the ddrives click - I can feel it in the belts and couplers. any advice - it is driving me nuts!!bloomingtonmike Posts: 77 Joined: Wed Dec 19, 2012 9:04 pm Private message https://reprap.org/forum/read.php?219,199995,199995#msg-199995 Sat, 08 Aug 2026 12:34:31 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?219,199995,201482#msg-201482 https://reprap.org/forum/read.php?219,199995,201482#msg-201482
instead of wiring series or parrallel

you could slightly mod it, draw out the logic pins DIR + EN + STEP, and "copy" this setup to another stepstick (out of ramps). so now using the same set of signals, use 2 stepstick to power 2 steppers. (i have not mod this myself yet, to do this you will need to prolly make it happen on a temp board outside the RAMPs PCB, like an external board)

and for VERY high current consumption steppers (more than 1A with ref to stepsticks), i found that adding larger capacitors do help in terms of stability. [3roomlabs.blogspot.sg]

then there is the micro stepping concerns due to use of correct Rsense on those stepsticks. and if you have good SMD skills, mod R4 to see if PWM frequency does improve stepping :D

[3roomlabs.blogspot.sg]
[3roomlabs.blogspot.sg]

my SMD skills are bad, i sacrificed a number of stepsticks lol

and of course the famous equation
Vref = A(stepper current) x 8 x Rsense

1.5volts = 2A x 8 x Rsense (=0.093ohms), i think you can use 0.1ohm Rsense if you use a Vmot voltage of 24-28v, cos when you use this voltage, Vref tends to go up to 1.65v. (or maybe this is an unintended flaw?)
it could be a good idea to know what Rsense values you have, like a certain stepstick i got, i assumed it was 0.05 ohm, but it wasnt, always good to check, you never know.]]> redreprap RAMPS Electronics Sat, 20 Apr 2013 20:42:27 -0400 https://reprap.org/forum/read.php?219,199995,201430#msg-201430 https://reprap.org/forum/read.php?219,199995,201430#msg-201430 akhlut RAMPS Electronics Sat, 20 Apr 2013 14:43:33 -0400 https://reprap.org/forum/read.php?219,199995,201420#msg-201420 https://reprap.org/forum/read.php?219,199995,201420#msg-201420 Maxx Mayhem RAMPS Electronics Sat, 20 Apr 2013 14:13:13 -0400 https://reprap.org/forum/read.php?219,199995,201405#msg-201405 https://reprap.org/forum/read.php?219,199995,201405#msg-201405
OSH park charged me like $5 for 6 boards.

If you want the files I'll post them to github. /EDIT/ The files are here.

[i.imgur.com]]]> akhlut RAMPS Electronics Sat, 20 Apr 2013 13:15:36 -0400 https://reprap.org/forum/read.php?219,199995,201279#msg-201279 https://reprap.org/forum/read.php?219,199995,201279#msg-201279 Maxx Mayhem RAMPS Electronics Fri, 19 Apr 2013 19:58:26 -0400 https://reprap.org/forum/read.php?219,199995,201276#msg-201276 https://reprap.org/forum/read.php?219,199995,201276#msg-201276 these a go, I've got to finish my mini CNC mill mechanics before I order one for an experiment though. :(

Hoeken has been working with the THB6064AH driver on his open source CNC mill electronics (which look pretty awesome BTW). His github is loaded with goodies.]]> akhlut RAMPS Electronics Fri, 19 Apr 2013 19:35:03 -0400 https://reprap.org/forum/read.php?219,199995,201274#msg-201274 https://reprap.org/forum/read.php?219,199995,201274#msg-201274 www.ecomorder.com]. I have ordered it, though it is back ordered to the supplier whom I believe is in England. Could be faster for you to get it direct? The page has no webstore accoutriments, but I ordered by paypal. They do host a large tech forum. As such I will keep you posted as to when it shows up. It is diy only, they do not sell it assembled.:P]]> Maxx Mayhem RAMPS Electronics Fri, 19 Apr 2013 19:16:13 -0400 https://reprap.org/forum/read.php?219,199995,200990#msg-200990 https://reprap.org/forum/read.php?219,199995,200990#msg-200990 akhlut RAMPS Electronics Thu, 18 Apr 2013 19:32:47 -0400 https://reprap.org/forum/read.php?219,199995,200975#msg-200975 https://reprap.org/forum/read.php?219,199995,200975#msg-200975 Maxx Mayhem RAMPS Electronics Thu, 18 Apr 2013 17:52:16 -0400 https://reprap.org/forum/read.php?219,199995,200788#msg-200788 https://reprap.org/forum/read.php?219,199995,200788#msg-200788
Just want to say THANKYOU to you guys for teaching me about my pololus!!! I have MUCH better setup pololus now.

I may soon replace the nema17s with something better suited to the pololus!!]]> BloomingtonMike RAMPS Electronics Thu, 18 Apr 2013 00:23:18 -0400 https://reprap.org/forum/read.php?219,199995,200744#msg-200744 https://reprap.org/forum/read.php?219,199995,200744#msg-200744
Have you thought about wiring your Z motors in series (1x current, 2x voltage) rather than parallel as is the default (2x current, 1x voltage)? This MAY get around your current issue, though still at 2A draw, you might be pushing the pololu form factor (except maybe with the DRV8825's - I've not played with them yet so YMMV).

Other option is to buy a decent stand-alone stepper controller/driver and use that just for the Z. you'll have to pull Z Step, Dir and Enable out from the pololu header yourself to go to the stepper controller/driver.]]> Cefiar RAMPS Electronics Wed, 17 Apr 2013 19:01:44 -0400 https://reprap.org/forum/read.php?219,199995,200708#msg-200708 https://reprap.org/forum/read.php?219,199995,200708#msg-200708 0.685v - Z
0.689v - Y
0.744v - X

This gets me reliable 750mm/s/s acceleration and 180mm/s movement on my wantai 42byghw811 motors. It goes faster but will occasionally skip a step (probably a jerk setting, but my plastic wont lay down at 180mm/s and stick well, so my moves are the only 180mm/s that I do in daily printing.

I have heatsinks and a computer fan blowing directly on my RAMPS board.]]> mitchese RAMPS Electronics Wed, 17 Apr 2013 16:56:25 -0400 https://reprap.org/forum/read.php?219,199995,200678#msg-200678 https://reprap.org/forum/read.php?219,199995,200678#msg-200678 Maxx Mayhem RAMPS Electronics Wed, 17 Apr 2013 15:28:17 -0400 https://reprap.org/forum/read.php?219,199995,200610#msg-200610 https://reprap.org/forum/read.php?219,199995,200610#msg-200610 Maxx Mayhem RAMPS Electronics Wed, 17 Apr 2013 11:11:39 -0400 https://reprap.org/forum/read.php?219,199995,200237#msg-200237 https://reprap.org/forum/read.php?219,199995,200237#msg-200237 akhlut RAMPS Electronics Tue, 16 Apr 2013 07:53:18 -0400 https://reprap.org/forum/read.php?219,199995,200232#msg-200232 https://reprap.org/forum/read.php?219,199995,200232#msg-200232
They were not happy with the stepstick drivers, but the pololus drive them well.

I will take measurements of my current settings, I set the current via trial-and-error - I turned them up until the motors didnt stall, then gave an extra 15 degree turn up. Working well for over 1 year, heatsinks and fan are on my stepper drivers but the fan is just extra insurance (they run without the fan as well, though I havn't run more than an hour or two without the fan).]]> mitchese RAMPS Electronics Tue, 16 Apr 2013 07:26:28 -0400 https://reprap.org/forum/read.php?219,199995,200064#msg-200064 https://reprap.org/forum/read.php?219,199995,200064#msg-200064
1.) Step up to a different driver. You might need to go up to a high-end driver like a THB6064AH solution if you really want to keep the steppers (I've seen them interfaced to RAMPS before and it looks like they work pretty well). But at around $35 each that can get expensive. You might try a DRV8825 based chip. Pololu sells them. I'm running Panucatt's version on my X and Y now and I've been really pleased. Supposedly they can drive up to 2.5A with sufficient additional cooling. I haven't been able to verify that though.

2.) Get a different stepper. Just make sure the stepper doesn't draw more than 1.5 ~ 1.6A if you want to keep the 4988 Blacks.

As a stop-gap, do you have a fan blowing on the drivers? That may help a little bit. And no fast moves.]]> akhlut RAMPS Electronics Mon, 15 Apr 2013 16:46:52 -0400 https://reprap.org/forum/read.php?219,199995,200038#msg-200038 https://reprap.org/forum/read.php?219,199995,200038#msg-200038
I have the black A4988 pololus with small heatsinks on them.]]> BloomingtonMike RAMPS Electronics Mon, 15 Apr 2013 15:28:51 -0400 https://reprap.org/forum/read.php?219,199995,200033#msg-200033 https://reprap.org/forum/read.php?219,199995,200033#msg-200033
[reprap.org]
[www.pololu.com]]]> akhlut RAMPS Electronics Mon, 15 Apr 2013 15:12:57 -0400 https://reprap.org/forum/read.php?219,199995,199995#msg-199995 https://reprap.org/forum/read.php?219,199995,199995#msg-199995
I have stepping up to left (not a ramp but like a step is off). Other times it goes crazy and randomly places the zozzle somewhere for a layer.

I have played with the pololu trim pots. I cant seem to get it right randomly. If I turn up too much the ddrives click - I can feel it in the belts and couplers.

any advice - it is driving me nuts!!bloomingtonmike

Posts: 77
Joined: Wed Dec 19, 2012 9:04 pm
Private message]]> BloomingtonMike RAMPS Electronics Mon, 15 Apr 2013 13:39:13 -0400