Servo troubleshoot


 

Bryan Mayland

TVWBB Hall of Fame
Whoa what?! Do you not see this trace here?
kw3CLrb.jpg


Your voltages are perfect now, so is there no trace or has the pad become disconnected somehow?
 

SPDecoste

New member
Whoa what?! Do you not see this trace here?


Your voltages are perfect now, so is there no trace or has the pad become disconnected somehow?

yeah sorry I meant there's no scratches on the line from SVO to Q5... but I looked into it and I think I might have burnt the circuit from Q5 to SVO.

I don't have any continuity from SVO to Q5... that might be the problem though
 
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SPDecoste

New member
I actually had a bad time with the bs170. I installed them reversed at first, so trying to take them out I burnt the board around them. That's why I replaced them! Kind of ashamed of what the board looks like right now :(, but I thought if everything was booting correctly it wasn't damaged. I guess it is damaged around the right hole of Q5...

Q1 and Q2 seems fine, pin left and middle have continuity for both and I don't see any circuit for right pin..
 
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RalphTrimble

TVWBB Diamond Member
Just clean up the board where you have burned it, remove any fragmented pieces of the damaged traces so they do not short things out, then put jumper wires in place to replace any traces that are damaged. Easy to do and will work just fine.
 

SPDecoste

New member
Just clean up the board where you have burned it, remove any fragmented pieces of the damaged traces so they do not short things out, then put jumper wires in place to replace any traces that are damaged. Easy to do and will work just fine.

Hope this will work! What should I use to clean the board? The way you say it sounds really easy, but I actually have no idea what I'm doing. I don't want to mess things up even more!

Is there a little tutorial or guide I could refer to?

Thanks!
 

RalphTrimble

TVWBB Diamond Member
I'm sure youtube has a tutorial on this sort of thing. Basically if I have charred/burned board I usually scrape away the burned stuff with a blade or metal brush, common soldering tools experienced guys may have, but you can get the job done with any number of common tools. Next, install you parts, solder up the parts where the traces remain, then use some small gauge wire (solid core makes things easier) to solder a connection where the burned up traces would have gone. Cat5 or phone wire make good choices as they are thin and usually solid core. Try to cut the wires to precise lengths so they sit neatly on the board so they wont get disturbed when handling it.
The most simple solution would be to remove the transistor and the resistor and solder a wire directly from the ATMega SVO pin to the SERVO pin on the CAT5 jack. The servo will work without the servo booster which is what that transistor or resistor make up, though it does help stabilize the servo over longer cable runs. I personally would get the booster back in there, as it is a very simple circuit, easy to hand wire or repair.
 

SPDecoste

New member
I'm sure youtube has a tutorial on this sort of thing. Basically if I have charred/burned board I usually scrape away the burned stuff with a blade or metal brush, common soldering tools experienced guys may have, but you can get the job done with any number of common tools. Next, install you parts, solder up the parts where the traces remain, then use some small gauge wire (solid core makes things easier) to solder a connection where the burned up traces would have gone. Cat5 or phone wire make good choices as they are thin and usually solid core. Try to cut the wires to precise lengths so they sit neatly on the board so they wont get disturbed when handling it.
The most simple solution would be to remove the transistor and the resistor and solder a wire directly from the ATMega SVO pin to the SERVO pin on the CAT5 jack. The servo will work without the servo booster which is what that transistor or resistor make up, though it does help stabilize the servo over longer cable runs. I personally would get the booster back in there, as it is a very simple circuit, easy to hand wire or repair.

I'll try to clean things up today. Thanks for the advices!

I guess I could use a jump wire from SVO to Q5 bs170 right hole?
 
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SPDecoste

New member
Success Update!

Everything is working right now! I jumped wired from SVO to Q5.

The weird thing is that the left pin on Q5 is 0.70V @100%
middle is at 3.28V and right pin at 0.50V.

The 1k resistor goes from 5V to 0.70V to Q5... is that normal?

Also, the servo is making clicking noises when @ 5% to 95%... Not sure why, I'll try the 47uf capacitor a try
 

Bryan Mayland

TVWBB Hall of Fame
Great! That left pin voltage sounds fine, it should be 5/3.3 * the right pin voltage +/- a bit. If the servo is jittery, a capacitor on the far end of the output (closest to the servo) usually helps that. If it is just buzzing, make sure it isn't binding and unable to move.
 

SPDecoste

New member
Thanks for all the help Bryan and Ralph! Very happy that everything is sorting out.

The servo is shaky a bit, moving 1 degree and making a ticking sound like it wants to move (the screw is not too tight)... Is this what could fix it?

WUnTASy.jpg
 

Bryan Mayland

TVWBB Hall of Fame
That's the thing, yes. I found that even 0.1uF took out almost all the jitters but up to 100uF is good, 6.3V or more.
 

SPDecoste

New member
470uf 35V did not make any difference!

I'll go to the regular shop when it opens tomorrow and get 47uf and 100uf 10V and 25V.

If it doesn't work I'll try Ralph booster!
 

Bryan Mayland

TVWBB Hall of Fame
If the 470uF capacitor didn't make a difference, a lower value one probably isn't going to work any better. I'm not entirely sure why they vibrate though, so maybe there's more magic in a different cap that could be more beneficial.
 

SPDecoste

New member
If the 470uF capacitor didn't make a difference, a lower value one probably isn't going to work any better. I'm not entirely sure why they vibrate though, so maybe there's more magic in a different cap that could be more beneficial.

I'll try a different mg90 today and the bc337/10k booster.

Update later today...
 

SPDecoste

New member
The servo I was using was a MG90d (ordered from digikey, it said it was a mg90s, but they shipped the d)

I bought a MG90S at the shop near my place and it was moving randomly. I installed the capacitor and now it's working great!

Only problem is I think it's a counterfeit because it doesn't fit properly in my 3d printer damper. The mg90d was a perfect fit. The 3d print is made for mg90 and mg90s. So it should fit properly in it.

So everything except the fit is working perfectly!

Can't wait to give this a try in a month when there will be less snow out here!

Thanks again for helping me through all of this and creating this awesome tool.

Cheers
 

RyanMichael

New member
So I’m having this same issue. Instead of starting a new thread I figured I’d just add onto here. Built my heater meter with no real issues. Plug in the blower and my servo unit doesn’t seem to work at all. I do not have a micrometer at the moment so I’m going a bit blind on stuff. I’ve tried two different cat5 cables with no luck. I’ve attached photos of the back of my board. Just looking for good first steps to try to resolve this. I’m assuming getting a micrometer is going to be the first step.
 

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Bryan Mayland

TVWBB Hall of Fame
So I’m having this same issue. Instead of starting a new thread I figured I’d just add onto here. Built my heater meter with no real issues. Plug in the blower and my servo unit doesn’t seem to work at all. I do not have a micrometer at the moment so I’m going a bit blind on stuff. I’ve tried two different cat5 cables with no luck. I’ve attached photos of the back of my board. Just looking for good first steps to try to resolve this. I’m assuming getting a micrometer is going to be the first step.
Well the soldering looks nice, but I'm not sure what you can test without a multimeter. If you're using a keystone jack to connect the servo, I'd say the problem is most likely in the punchdown on the keystone given how nice your soldering looks.
 

RyanMichael

New member
Well the soldering looks nice, but I'm not sure what you can test without a multimeter. If you're using a keystone jack to connect the servo, I'd say the problem is most likely in the punchdown on the keystone given how nice your soldering looks.
Well thank you. I haven’t done soldering like this since high school.. so over 20 years ago now. It was fun to get back into it. I have a punchdown tool that I used for building some network runs and that’s what I used on the keystone jack. I re-punched the power and servo line, but not the negative. Since the blower is running and hooked up to the same negative line as the servo I assumed that was working just fine.

While typing this I thought hell.. just re-do the ground punch again because it costs me $0. That was it.. ground wire wasn’t punched down correctly.

Thanks Bryan!
 
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