How to make servo lives longer ?

Hi I am new to arduino and servos. :slight_smile: The servos die within 2 weeks in my toy project. I found some advice here in this forum, and changed a bit the circuit (figure). Sorry for the rough drawing.

Aim of my toy project is to let a servo drive a light rod up and down, which touches the fixed broads on both side and being blocked to a stop (figure). This movement has a period of a few seconds and runs 24/7. The servo is TP-SG90 continuous type.

How they die:
My first SG90 dies in 1 week and becomes hot when "dead". I was using my 1st circuit. The period is around 3 secs at this trial. I thought it was "dead" since the USB-powered arduino cannot drive it any longer. So I changed it and rewrite my program to a period of 10 sec. I increased the servo idle time and decrease speed in the servo program, so that the SG90 pushes less and lighter hard against the broads (afterwards I have an external power capable of high current output, and the SG90 moves again, but in some unpredictable manner and cannot be reused.)

My 2nd SG90 dies under the 1st circuit, too. The yellow arduino L-LED light flashes, and I suspect the driving current is not high enough. When I use an external power, the SG90 shakes lightly but does not move much. So I changed to another servo.

My 3rd SG90 is using the 2nd circuit and it moves fine at the moment.

I just know that the servo can be opened, and I shall open them to study what happened internally.

My question is : What should I do to make SG90 live longer ?? what have I done wrong driving it to death?? Do high loading / good power / polymer gear matters and any other things I missed ??

I know The gears are polymer but they should last longer than months with this very light loading. :o If this is impossible, may be I should consider some other servos type. May be metal gear could be better. Any suggestions?? Thanks ! :slight_smile:

I get a max of 100 continuous hours of operations out of plastic geared servos.

I have 3 metal geared servos going on 3 years of continuous operations.

Idahowalker:
I get a max of 100 continuous hours of operations out of plastic geared servos.

I have 3 metal geared servos going on 3 years of continuous operations.

Could you suggest some models so that I can try on ?? I saw some but they seems to be big and expensive... thanks

Metal geared servos are more costly than plastic geared servos but than count in replacement costs every 100 hours...

https://smile.amazon.com/gp/product/B073F92G2S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 is one kind of metal geared servo. I've had good luck sticking with the LewonSoul servos. I use 1 5V (7805) regulator to power 2 servos, has worked pretty good so far; with small loads.

The most obvious alternative to an SG90 is the MG90, same size and not much more expensive.

But from what you say ("being blocked to a stop") it sounds like you are stalling the servo at either end of its travel and no servo will stand that for very long. Stall is the worst case condition for the motor and the gears.

Steve

Idahowalker: Thanks :slight_smile: This metal servos seems cheap enough and I shall try it.

slipstick: Yeah my fixed broads altitude can be relocated manually, although not very frequently. So the servo program will press on the broads a little bit after touching. I have written margin allowance in the program to ensure the arm touches both broad, then the arm will stop and rest on the broad. If that leads to stalling, I shall try to shorten this stalling time as much as possible. However it seems I cannot avoid the stalling.

@tompuma

Consider limit switches in some form to hold the servo at the end points.
Also maybe add pictures as I have no idea what "broads" are in this context.

Could you also take a few moments to Learn How To Use The Forum.

Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

I’ve had MG996R servos last for > 1.5 years and still running.

Have had very poor success with MG90s.

ballscrewbob:
@tompuma

Consider limit switches in some form to hold the servo at the end points.
Also maybe add pictures as I have no idea what “broads” are in this context.

Could you also take a few moments to Learn How To Use The Forum.

Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

Thanks ballscrewbob for the advice and beginner guides :slight_smile:
I shall study them.

larryd:
I’ve had MG996R servos last for > 1.5 years and still running.

Have had very poor success with MG90s.

OIC, I shall check out MG996R :slight_smile: Thank you
After known the SG90 will only last for 100 hours, I've already switched it off and looked around for more durable servos. Your advice is very just-in-time.

So when the gear is metal, what kind of care should I take to extend its lifetime??
e.g. extreme load / weak supply / oiling the gear etc., do these factors matters??
Many thanks :slight_smile:

When new, I take servos apart and add lithium grease if it gears need it.

I've not done anything to the LewonSoul metal geared servos to make them last as long as they have.

After one month of testing, I have accessed to a MG90 and two MG995 with metal gears. However, they are alternative brand of the original brand, so they are cheaper. I connected them one by one to the 2nd circuit and follow by appropriate change to my servo program. They work well at first, but all failed after 2 days. Now they are not completely dead, but they just move in a crazy manner, e.g. stuck at two ending positions or at some middle angle, and then keep drawing current form the power. I reset the servo and then they moved again for a few cycles, and then will go crazy again. They will become warm after sticking for a few minutes. These are the observations.

I am trying to understand why they stop working. My power supply is a V and I-tunable one, and seems sophisticated enough that this is not the source of problem. I limit the max current to 1A at 5 to 6V, so it shouldn't have burn out the servo control circuit.

My question: I suspect all these servos are certified dead?? Any suggestions on how to fix / check them?? Thanks.

I am trying to get access to a servo tester and a new servo TD8320MG. Hope I can find a working servo in the coming weeks.

So you've limited the current supply to several servos at 1 amp when each servo needs about an amp of power?

Show a picture of your setup.

Using a breadboard to supply servo power?

Idahowalker:
So you've limited the current supply to several servos at 1 amp when each servo needs about an amp of power?

Show a picture of your setup.

Using a breadboard to supply servo power?

Thanks for the replying. My system is as setup in the image at 1st post, and I am using the 2nd circuit. The external power is some DC Supply similar to this one :-

The work scenario is as shown in the image, too. The servo drives a stick up and down. It hits the upper & lower planes like every several seconds, depending on the servo program.

Should I increase the ext.power current limit to 2A ?
Should I set its voltage to a bit higher, like 6V?
I am very concerned about the reliability of the servo, and I can try anything that can extend its life.
Currently I am surprised that SG90/MG90/MG995 all dies in a week or two... is this life time expected for common servos?
I am looking for a servo that can do this task for a year or two, the longer the better.
Please advice me and thanks.

In fact I am quite frustrated by this servo lifetime problem, even in such simple task like this. This makes me wonder how drones and model planes can be built with such unreliable servos? I guess I must be missing something...

tompuma:
slipstick: Yeah my fixed broads altitude can be relocated manually, although not very frequently. So the servo program will press on the broads a little bit after touching. I have written margin allowance in the program to ensure the arm touches both broad, then the arm will stop and rest on the broad. If that leads to stalling, I shall try to shorten this stalling time as much as possible. However it seems I cannot avoid the stalling.

If it is essential that the item being moved by the servo makes contact at the end of the stroke then you should have some resilience between the servo arm and the item - for example a flexible wire - so that when the item makes contact the servo can comfortably move a little further without being forced to stop.

...R

However, they are alternative brand of the original brand, so they are cheaper.

Tower warns you on their site that there are many low quality counterfeit servos being sold. Obviously they would say that, but perhaps in your case that's what bit you.

tompuma:
Should I increase the ext.power current limit to 2A ?

1 amp per servo is what I do.

tompuma:
Should I set its voltage to a bit higher, like 6V?

6V would be fine if the servo is rated for 6V.

tompuma:
I am very concerned about the reliability of the servo, and I can try anything that can extend its life.
Currently I am surprised that SG90/MG90/MG995 all dies in a week or two... is this life time expected for common servos?

Me too. My metal geared servos running on 5V have been operating for 3 years and 2 months now. I only have got the plastic geared servos to run 100 hours or so.

tompuma:
I am looking for a servo that can do this task for a year or two, the longer the better.

Yuppers.

Thank you all for the advice. :slight_smile:
Perhaps the following are what I shall try.

  1. Better quality servo model and brand. The next one may be TD8320MG.
  2. Some "cushion" at the touching points so that the servo may see less hard time when hitting the obstacles.
  3. The MG90 and MG995 can still move, I suspect the control broads inside the servos may be dead. I shall open them and check if I can fix them.

tompuma:
In fact I am quite frustrated by this servo lifetime problem, even in such simple task like this. This makes me wonder how drones and model planes can be built with such unreliable servos? I guess I must be missing something...

Most drones don't use any servos. And model aircraft servos are not deliberately stalled at each end of the travel and most often only run intermittently for 5-10 minutes at a time. Basically you're using your servos in a way the designers never intended.

Steve