# A jam burnt the motor driver board?

**URL:** <https://forums.maslowcnc.com/t/a-jam-burnt-the-motor-driver-board/3106>\
**Category:** Troubleshooting\
**Created:** [April 3, 2018, 6:03am UTC](https://forums.maslowcnc.com/t/a-jam-burnt-the-motor-driver-board/3106 "2018-04-03T06:03:31Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![Keith](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/keith/32/1332_2.png) [@Keith](https://forums.maslowcnc.com/u/Keith)\
**Post date:** [April 3, 2018, 3:31pm UTC](https://forums.maslowcnc.com/t/a-jam-burnt-the-motor-driver-board/3106/7 "2018-04-03T15:31:51Z")

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> [@madgrizzle](#):
>
> incorporate a microswitch

That’s a cool idea. Might be tough to find an input on the arduino if you are implementing an auto z-axis zero.

A chain guide that is a close fit to the sprocket should also work to peel the chain off the sprocket before it wraps.  
Man I wish I had AutoCAD at my current job, but here goes:

 ![Untitled](https://canada1.discourse-cdn.com/flex031/uploads/maslowcnc/original/2X/1/172197ab822ba17066e08c5e418f5a86a59ee8ab.png)  
where the large grey circle would provide a backing for the chain to keep it feeding parallel with the sprocket.  
Mind you, I think that @mrfugu’s idea of putting [the roller right next to the sprocket](https://forums.maslowcnc.com/t/unistrut-frame-designs/1267/27) works to avoid skipping as well as keep the chain from wrapping. I have been fortunate to only have had the chain start to wrap once while I was right next to it an able to pull it off (this was before I implemented MrFugu’s roller placement), but I am pretty sure that the roller would keep it from wrapping on itself.

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