Hi, I have completed printing and assembly of SP11, but am having a problem with the second hand taking about 1 min 17 seconds to complete one revolution. Similarly, watching the stepper gear rotate, it rotates slower than the 6.9 rpm the manual indicates it should (by eye and a stopwatch it appears to be closer to 5.4rpm). I am using the cnc shield, with arduino nano. I purchased a 1.8deg stepper motor (model #17HS15-1504S-X1) , and have the pin setup on the cnc shield set to option 5 [0101] as indicated in the manual. When I look at the debug info in serial monitor, it does appear to recognize that I have set option 5 for speed, and when it counts the seconds and logs each minute, they seem accurate to my stopwatch at 1 minute per debug line. It just seems to be my motor is not running at the expected RPM for the setting, and I am unsure what else to troubleshoot. Any suggestions are welcome, if there's any other info I can provide, please let me know. -J.
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Hi Jarret,
Your description is great. It appears that you have done all the right things.
A couple of questions:
What version of the algorithm are you using? Older releases were not set up for SP11.
Does the debug monitor show a mixture of + and -? That would indicate that the RTC is properly getting tracked. Each debug line taking 60 seconds is another good sign. The algorithm could be about 5% off if the RTC is not tracking. A 30% error likely indicates something else.
Stepper motors are very precise. Give them 200 full steps and they should rotate exactly one complete revolution. Are you losing steps? The motion might be a bit jumpy instead of smooth. Increasing the potentiometer setting slightly would help.
Did you build SP10 or SP11? They have different gear ratios and need different jumper settings. Try other settings.
The friction clutch is after the second hand, so it is not a likely source of the error.
That is all I can think of right now. Let us know if anything works.
Steve