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« on: March 01, 2010, 08:46:04 AM »
Hi, It's not desirable to disconnect power from steppers at any time, position will be lost even just a small bit each time they are shut off eventually leading to
large errors.
Some drivers have an internal current limiting circuit to reduce power when not in motion so if you have one of these drivers, no worries.
If your driver doesn't have this circuit then you should set the current through the stepper to the steppers specs.
Current rule of thumb is if you wrap your hand round the stepper and then count 30secs before pain begins to set in. Then thats fine.
Saying that, A while back when cnc was new to me I built my own stepper drivers to power 3 Nema34 size steppers current at 4amps/phase to retrofit an old mill.
When the steppers arrived I found 8 wires "oh, 4 phases" I thought and then built the drivers to supply 4amps to the 4 phases. Little did I know that the steppers were 2 phase so my current calcs were way off.
So when I do the hold the stepper trick I can only count to 3, Strangely enough though, Until recently the mill had been used nearly every day for my business for nearly 10 years, Its only gathering dust now as I bought another mill and have converted to servo drive.
Cheers
John
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