Servo chatter/sporadic movements when changing %


 
J

Jeff.Ro

TVWBB Member
Just got my 3D prints back and put the servo and blower together. Just setting everything off of manual fan mode for now. Blower works fine, ramps up as it should. However, the servo with every change in percentage will jump and chatter and even move to wayyyy off where it should be. I've even tried taking the servo out of the blower housing to see if anything was bound up while mounting and got the same results.

I had done some searching and looks like the power supply is one potential problem area. I have been using one I found in my random electronics/wire box. Someone had success with this power supply fixing some servo problems in another thread so it will be here Monday. http://www.amazon.com/exec/obidos/ASIN/B00Q2E5IXW/tvwb-20

I should note that the servo does not make any noise/chatter/move sporadically except when the % output is changed. I'm uploading a video to YouTube and will post a link shortly.
 
Jeff.Ro said:
You having issues with chatter/jitteriness?
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Nah, I just need to replace my PSU because it's got some weak points in the wiring in areas I can't fix, and I accidentally melted some of it last year during a competition. I bought this HM from someone else originally and I cannot locate the PSU online. It's a 2amp so I'm of course looking for a 2A to replace it. I wanna make sure it has no noise issues.
 
Jeff.Ro said:
New power supply I listed above didn't help. What do you guys think? It's a Towerpro MG90S servo.
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Ya know, now that I think about it, WBegg was mentioning to me previously that the MG90S servos sometimes are crap, so you might get a bad one. I'm not sure what the exact symptoms were though, so Will, if you see this, perhaps it's a bad servo?
 
You might be thinking about me, not Will. I use SG90 servos exclusively with the MicroDamper because quality control on the MG90s is crap.
 
Oh I should also mention, that if you have it set "inverted" or vice versa from what it should be you can get some weird movement as well.
 
SteveCK said:
You might be thinking about me, not Will. I use SG90 servos exclusively with the MicroDamper because quality control on the MG90s is crap.
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Nah, it was def Will, in an email conversation we had outside of these forums. But I'm not surprised to see that others have the same issue. I've gotten lucky and the two I own have been flawless....so far.
 
NickMV said:
Ya know, now that I think about it, WBegg was mentioning to me previously that the MG90S servos sometimes are crap, so you might get a bad one. I'm not sure what the exact symptoms were though, so Will, if you see this, perhaps it's a bad servo?
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Yeah, that was me. The MG90 servos are pretty much the most copied (pirated) servos on the market. Just because it says "Tower Pro" doesn't mean it's the real deal. It's pretty much a toss up if purchased from places like E-bay (chinese vendors).

SteveCK made a very good point in one of his other posts in that although the MG90s has metal gears, and a bit more torque than the SG90, it's not really necessary for opening and closing a damper. After all, your not putting it in an RC airplane that's gonna get thrashed with bad landings and such. An SG90 ought to be more than sufficient for a damper.

I'm currently testing one of these from HobbyKing. It's supposed to be similar to the MG90 digital servo (greater precision). It is a bit noisier than the Tower Pro, but seems to be working as advertised thus far. The mounting dimensions are the same, but there is a slight variance in the measurement of the stem (for lack of a better word).
 
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WBegg said:
Yeah, that was me. The MG90 servos are pretty much the most copied (pirated) servos on the market. Just because it says "Tower Pro" doesn't mean it's the real deal. It's pretty much a toss up if purchased from places like E-bay (chinese vendors).
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I've noticed its more than ebay. I've even found Amazon doesn't source quality MG90 servos.
 
I have a very similar issue - haven't been able to fix it. Were you able to resolve this? Would *love* to get this fixed.
 
0s884G
Yeah, the fix was new servos. Got a MG90S four pack off amazon for not much more than double what I paid for the single one.

The two amp power supply didn't help with the chatter. Although I do appreciate the 8' cord it has.
 
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Can I ask about the behavior you were seeing when your servo chattered? I have built two HMs, a V4.2 and v4.3 and see the same behavior on both units. Sometimes, but not always, the servo chatters but when this happens I am seeing the display blinking and my raspberry pi is loosing power and restarting. I don't think I see this issue unless the raspberry pi is attached, so it has to be somewhat of a brown out issue. I am using the power adapter suggested on the wiki. I'm going to try rewiring my servo blower tonight to see if there is a short in the jack i made. I am using a micro damper.
 
Chris S (AsstroChris) said:
Can I ask about the behavior you were seeing when your servo chattered? I have built two HMs, a V4.2 and v4.3 and see the same behavior on both units. Sometimes, but not always, the servo chatters but when this happens I am seeing the display blinking and my raspberry pi is loosing power and restarting. I don't think I see this issue unless the raspberry pi is attached, so it has to be somewhat of a brown out issue. I am using the power adapter suggested on the wiki. I'm going to try rewiring my servo blower tonight to see if there is a short in the jack i made. I am using a micro damper.
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Sounds like you've either a short somewhere, or you just have a bad power adapter. These power adapters are known to be crap, if you have a spare 12v 1 or more Amp power adapter around your house give it try. Many electronics run off 12v so check them all - routers, modems, cordless phones, etc etc
 
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