Everything working perfect except...Servo twitching.


 
J

Justin F

New member
I have my RD build all done and working extremely well. But after about 10 min of operation, the servo started twitching at a very regular pace. This continued overnight for another 12 hours, with the servo still working. The servo continues to work fine, but I am sure it will burn out. I've tried two other servos and get the same thing. Help?

Attached is a video of what is happening also...

P.S. - thanks to Ralph for all the help - his stuff is amazing!
 
First you need to make sure the servo is fitting into the roto damper barrel snug but not tight where it needs to be forced in. If you force the servo into a tight hole it will make it bind and jitter. Next you need to make sure the servo isnt tightened down to the point that the barrel has resistance to turning, it should rotate as freely when assembled as it did before the screw went in. If not then loosen the screw a bit. Finally, you need to make sure the SPD settings in your HM config are not trying to push the servo beyond its operational range. To test this set the HM to 0% and then unplug the Roto Damper, you should be able to rotate the barrel toward the closed position a little bit, set the HM to 100% then unplug the RD, you should be able to rotate the barrel toward the open direction a little bit. If you found either direction you are at the end of your range then adjust that SPD setting appropriately to move that setting into the operational range. You may have to remove and reorient the barrel if you run across this situation.
 
Hey Ralph - thanks for the quick reply -

* Checked to make sure there was no forcing of the servo in - fits loosly
* Loosened the servo screw and make sure there is no friction between the two bodies.
* Tried many different SPD settings, starting with 800-2400. Even at this, I get the right rotation (a but short, but for testing good enough). At first in resting it will make no noise. Then in either open or close setting, it will do this. I tried manually helping the servo to see if it was stuck - wasn't went right back. I then tried different SPD settings 200-1000 on the low end and 2000-3200 on the high end - same thing.
* I tried with a brand new servo, same thing.

Note the rhythm of the twitches - very regular (usually the out-of-range SPD issues I have seen are more constant jamming or effort sound. Any other ideas? Perhaps some other jump or issue?
 
What version of the Heater Meter are you running? Do you have LinkMeterV12 and the latest firmware installed? I know the servo was much more twitchy with the older software.
 
also make sure the wires for the servo or blower aren't causing drag, it doesn't take much pull on the wires to make the servo twitch...
 
If you are running your probes through the CAT5 cable poor connections where you piggy backed the wires could cause the pit temp to fluctuate and thus make the servo over active. Noise on your probes in general could cause the same thing. And not all Tower Pro MG90 servo's are created equal, I've had strong ones and weak ones, noticed different printing, slightly different sizes, the shafts pull out on some but dont on others...

PS Again, what version HM are you running?
 
more info - interestingly enough, this only happens after I plug in the thermocouple. Doesn't do it until I do. Then, it will continue to do this even after unplugging the thermocouple, and even after unplugging the CAT5 unit. It also happens when plugging the thermocouple into the main plug on the HM (after flipping the switch). Guh - think this is gonna be hard.
 
I was following you until you said the servo was twitching after you unpluged the CAT5 unit? Don't think that is possible?

Try a different power supply if you can find one... Some can cause noise issues, noisy pit probes make for jittery servo's. Also, using a servo and the blower kinda pushes the 1A power supply a bit, I think that should be updated to a 2A model standard IMHO for just a buck or two or maybe even the same $....

I was also asking what version of the HM BOARD are you runing? HMv4.0/.1/.2?
 
RalphTrimble said:
I was following you until you said the servo was twitching after you unpluged the CAT5 unit? Don't think that is possible?
Click to expand...

Sorry - it stops when removed, but when plugged back in, starts again, even with the thermocouple removed.

RalphTrimble said:
Try a different power supply if you can find one... Some can cause noise issues, noisy pit probes make for jittery servo's. Also, using a servo and the blower kinda pushes the 1A power supply a bit, I think that should be updated to a 2A model standard IMHO for just a buck or two or maybe even the same $....
Click to expand...

Will do - will look for one on amazon.

RalphTrimble said:
I was also asking what version of the HM BOARD are you runing? HMv4.0/.1/.2?
Click to expand...

Sorry - 4.2.4
 
I tend to prefer the old school heavy wall wart power supplies over the modern lightweight switching mode units. Check around the house, you may have one, old answering machine, cordless phone, router etc... 12VDC Tip Positive, 2A or better is nice, but give anything your find at 1A or better a try...
 
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