A3977 Woes

[jcdillin]

Hello everyone,

First post here, i've spent quite a while planning and lurking but now i'm at the phase of building my controllers and i'm having some serious problems. I was hoping maybe someone that has used these 3977 controllers from allergo might be able to help.

I have followed both the schematics from allergo and the schematics from pminmo.com just to be sure i'm using all the correct values. The only thing I changed from the pminmo design is that mine is all SMD and double sided. I am using all the same values for parts. The problem I am having is this, when I apply power and pull the enable pin low the motor stiffens up just like it is supposed to. But when you try to step the motor it kind of just jumps in place and after a couple times trying to step it will just start humming and the chip will get very hot very fast. Now I double checked my vref and it is set at 2.8V for 2A current limiting. I also tried it in full step and microstep with similar results. I am running this all off of a 15V 10A supply so I dont think it's a lack of power. I also tried swapping phases on the stepper just to be sure I didnt have something backwards.

Also I just want to mention that I just have this stepper out in the open and not attached to anything.


Thanks for any ideas that you can give

[pminmo]

Physical layout problems in all probability. Just because the components and the schematic the same, physical layout is just as important.