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So when i added a part cooling fan to my build, the signal noise started causing my servo to twitch relentlessly even with the servo cutoff set and it happened to burn up or the gears stripped out tonight.
Anyone have any ideas on how to isolate the servo from the noise?
http://3dprintboard.com/attachment.p...tid=4617&stc=1
Sorry it turned
I suggest the use of ferrite cores. Sounds like the new fan is throwing some serious electrical noise! Actually, I would change the fan.
If you keep the fan, wrap the wires in a ferrite core 3-5 turns. Also, investigate the quality of the power supply and how close to limits your new fan may have brought the situation...
Association of the servo jitter to installation of the print cooling fan is interesting. The servo signal is a time domain pulse width, where the rotation angle desired from the servo is set by the width of the digital signal. "Noise" on the servo signal has to be something that affects the timing of the edges on this pulse width. Noise coupled onto the signal line when it is logic high or a logic low would likely have little effect. It would have to be strong enough to be interpreted as new timing pulses by the servo - I would think it would take a strong noise source and pretty effective coupling to accomplish that. Some questions and thoughts come to mind -
1. Does the servo jitter occur only when the fan is on?
2. Does the servo jitter occur only when the fan is on, but only at speed setting(s) other than full speed? If so, this would confirm there is an association with the PWM speed control for the print fan. In addition to the electrical noise coupling possibility, it could also be that the timing of the servo pulse is being affected by processor loading or alterations in interrupt timing in support of the fan PWM signal.
3. If it is affected by the speed of the print fan, try toggling the state of the configuration.h #define for FAST_PWM_FAN. If you have it commented, uncomment it. If it is uncommented, comment it out. This will change the timing of the PWM signal for the print fan. What effect does this have? Note that leaving it uncommented should help minimize audible PWM whine from the fan.
4. Does the servo jitter occur when you do a print without ABL corrections? If not, that might suggest whatever is affecting the servo timing pulse is with the ABL processing, not the print fan.
I would use strands of cat5e cable, twist 3 seprate strands together and replace the wires on the servo. It should at least help with noise reduction. You can also use a ferrite core on the fan itself and wrap the fan header around it. There are also inline ferrite cores that are much heavier that should do the trick. Sounds like the fan is emitting quite a bit of noise.