Stepper driver

[billr]

What I am seeing on the MS2 schematic is a UDN2016. I can't find that listed anywhere, have looked on the web a bit in general, and at the Allegro site in specific. That would be an old Sprague P/N, of course, but Allegro seems to show other obsolete UDN devices. So, what is that chip on the MS2 and where can I find a data-sheet for it?

What is the stepper chip on the MS3? I can find it, of course, by opening my case, but please save me from that chore!

I believe the the chip in the MS3 is a true stepper-driver, with P&H type current limiting and maybe micro-stepping; whereas the chip in the MS2 is only an H-bridge. So, I'm wondering if there are some subtle differences in how those can control a stepper and how those may be causing a problem if there are other problems in the stepper circuit or its mechanical operation. Give me the chip numbers so I can muse on it some more, please.

[jsmcortina]

As I said in the other post, MS2 and MS3 are identical. The UDN2916 was superceded by a part that does exactly the same thing, but is lead free. They gave it different part number which causes confusion - A4970SLBT.

James

[billr]

Okay, I understand now that they both use the UDN2916 or modern equivalent. Does the CPU and code for both provide essentially the same current control available using that chip? Do they do half-stepping, or better? The schematics are just too blurry for me to read everything clearly; worse if I print them out as black-only, the colors become even fuzzier grays. I could (and do) believe that is a "9" on the schematic (UDN2x16), but it looks more like a 0. The 6 is also hard to read. I will do a screen-grab if you want to see what I'm seeing.

[jsmcortina]

Current limiting and half-stepping are not used.

The existing MS2/Extra and MS3 stepper code is mostly the same as the MS2/BG code except we fixed up some bugs and allowed the stepper motor to run backwards too. It's working ok on many many installs too !

James

[billr]

"Current limiting and half-stepping are not used."


That is while moving, correct? Doesn't the MS3 reduce current if "hold" is selected?

[jsmcortina]

"Current limiting and half-stepping are not used."


That is while moving, correct? Doesn't the MS3 reduce current if "hold" is selected?

It sends a 50% duty signal to the "select" wire of the chip to give lower current and reduce heating in the stepper motor.
With "always on" a stepper became too hot to touch, with "hold current" it is just warm.

James

[Six_Shooter]

The datasheet is available. I found it online a few months ago when I wanted more info on the stepper driver IC. Just type the part number into the Google machine and you'll find it.

[billr]

My problem there was that the schematic in the manual is too blurry to read some of those small details. I read it as "UDN2016", but it is actually a UDN2916.

[racingmini_mtl]

James gave you the replacement part number and the datasheet for that is easily available too.

Jean

[billr]

Again, I know what the device number is, where to get a datasheet, what to replace it with, and where to buy one.

Does nobody want to comment on my contention that the schematic in the manual is too blurry to be useful in some cases? I'll post a screen-shot of what I'm seeing, if you want.

[billr]

Here it is anyway. Yeah, I zoomed in, but it is even less readable a normal scale.

Understand, I am not eager to criticize the hard-working developers; but when I come across something that may need improving, I feel it is beneficial to all to point it out

[racingmini_mtl]

I do agree that the schematics are blurry and sometimes hard to read. And I also think it is unfortunate that it is not possible to have the same readable ones that were available before not even in the pdf version of the manuals.

Jean

[Six_Shooter]

I have not had any issues reading any of the MS schematics.

Try reading the wiring diagrams in any of the Nissan FSMs for the Datsun 240Zs. THOSE are blurry.