So I have a question that I hope someone with more experience can help me out with. The machine is a minimill running GRBL 1.1 on an Arduino Uno and a Protoneer CNC shield (3.51). The mill is equipped with hand wheels on all three axis. This is important. The mill has been in use and working for quite sometime now. However, on occasion I have burned a Pololu style motor driver by using the hand wheels. I am pretty careful not to use them, but yesterday, with the machine off, I retracted the Z axis using the hand wheel. About 1/2 way through my intended movement, I noticed that all of a sudden it got very hard to turn the axis. I knew almost immediately that I had lost another motor driver as this was the same symptom as in the past. Here is where I screwed up. I should have simply changed the Z axis driver (remember the power was off). Instead, like a dummy, I applied power and was treated to a smoke show of the Z axis driver. I replaced the driver and still had problems. This time I lost the Arduino Uno as well. In fact, when I changed the Arduino, I decided to try moving the GRBL programmed chip so save myself reconfiguring the system. This actually sort of worked. I say sort of because after getting everything back together I could not get Y-. No matter what I tried, Y+ or Y- it always moved Y+. I have experienced this behaviour before and always tracked it down to a bad motor driver. I tried changing that first, but the problem persisted. I even tried reburning the chip with a new GRBL install. No luck. In the end, I put a new Atmega chip in with a new install of GRBL and finally resolved the issue. So, my question after all of that. Should I NOT use the hand wheels, or is there a safe way to use the hand wheels? It should be noted, I have used them lots for small slow movements. The problems always seems to be when I try to move an axis quickly or a long ways. Too much back EMF from the motors I suspect.
yup lesson learned. I knew right away too. Good thing I had some spares laying around. I have an Openbuilds Blackbox controller intended for another machine. Is this controller less susceptible to this problem or about the same? Thanks for the reply
It is less susceptable (Has TVS diodes across the output to clamp reverse voltage) but its still not recommended
if you have to use the handwheels, then SLOWLY. the faster the motors spin, the more voltage they produce, and that is what kills drivers.
