TomasHubik

Servo 45° limit by force

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Hi guys, 

can I damage PF Servo motor if I will force to turn it only 45° as you can see it on image bellow? Green axle will be connected to servo that will be fixed to red part: test.png

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I will gear it down appropriately, rather than force limiting my servo... nothing good will happen to stalled motors...

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Thermal protection will kick in before you can damage your motor like that, but unless it is a limited space solution I would gear it down for being safe with crappy servos

Edited by LXF

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Hi Guys! Thanks for replyes. Unforutnatelly I'm extremely limited with space and gearing down is not possible. I Will try to figure out some workaround maybe using 45590

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1 hour ago, TomasHubik said:

Hi Guys! Thanks for replyes. Unforutnatelly I'm extremely limited with space and gearing down is not possible. I Will try to figure out some workaround maybe using 45590

Not sure after that, I always gear down mine after I found it does 80° on a turning circle.

I use a 16:20 ratio, but you will need a 2:1 ratio probably.

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Nothing really bad will happen with servo-motor and no thermal protection will kick in, because it is servo:) When servo-motor is being stopped at non-90 degree angle only "bad" thing that is happening is that it power consumption raises up to 1A for only about 0.25s and then it stops consuming power. So I think you can use servo-motor in a such way.

Source: http://www.philohome.com/pfservo/pfservo.htm

But still I would prefer using some ways to save 90-degree motion. I will show you my favorite way of how to reduce servo-motor's motion without gears and with minimum slack when I get to my parts:)

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2 hours ago, kbalage said:

I would definitely add a clutch gear to avoid any damage

That would defeat the return to center function of the servo, and make it all pointless

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Why not use the PF remote with speed control?

64227.png

If you only turn the dial a little bit, it will make the servo turn less than 90 degrees (in seven steps left and right).

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3 hours ago, Limga said:

Nothing really bad will happen with servo-motor and no thermal protection will kick in, because it is servo:) When servo-motor is being stopped at non-90 degree angle only "bad" thing that is happening is that it power consumption raises up to 1A for only about 0.25s and then it stops consuming power. So I think you can use servo-motor in a such way.

Source: http://www.philohome.com/pfservo/pfservo.htm

But still I would prefer using some ways to save 90-degree motion. I will show you my favorite way of how to reduce servo-motor's motion without gears and with minimum slack when I get to my parts:)

Thanks a lot man, will wait for your tip! I will try the servo force stop later today.

The problem is, as I wrote it above, I'm really limited by place. I tryed to use 45590 which works well but thanks to flexibility,  axle turns when stuck on obstackles. 

 

Thank you gus for your posts!

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I think you'll be fine driving it directly, I had the same question a while back and used the servo with limited physical travel, without any damage to the motor.  I tried gearing the servo down but it was a pain in the neck because the axle of the second gear was never aligned with the first, resulting in a car that never drove straight. Maybe there's some magical gear ratio that fixes this issue, but I don't remember finding it (edit: 3 gears will do it, but it takes space).  The only alternative to gears is a linkage system, but that will increase your build size quite a bit.

Edited by BusterHaus

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Speaking from experience you can ruin the return to centre function of a servo by forcing a smaller turning angle. I wouldn't recommend it. I now have a servo that will work for angles up to 45 degrees, but once I try to use it for 90 degrees it simply stays in the 90 degree position. I should add that this was after extensive use that the return to centre started to fail. So if you absolutely have to use this solution, use it with moderation.

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1 hour ago, Zero (Zblj) said:

try using 12 and 24 tooth gears. You will get a 1:2 gear ratio AND axles will be aligned.

It's very close to having the axles aligned, but the gears are not in line.  The motor or the link to the steering rack would have to be off center.

34540742303_d2b035e834_o_d.png

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1 hour ago, Appie said:

Speaking from experience you can ruin the return to centre function of a servo by forcing a smaller turning angle. I wouldn't recommend it. I now have a servo that will work for angles up to 45 degrees, but once I try to use it for 90 degrees it simply stays in the 90 degree position. I should add that this was after extensive use that the return to centre started to fail. So if you absolutely have to use this solution, use it with moderation.

This problem occurs quite often and the limiting angle is not the main reason. The reason is the bad engineering inside the servo. Unfortunately, my English isn't good enough to explain it correctly, but I'll try.
Servo obtains it's position by turning on 15 conducting segments that are not connected between each other. When some segments become connected by any reason (bad quality) servo-motor can't know that it is in the 90 degree position, for example. So if you want to repair your servo you need is to disassembly it (very unpleasant experience) and make sure that segments are not connected with each other by scratching their borders with a needle's end. I did it with my friend's servo that had such problem and it worked fine. 

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8 hours ago, Limga said:

So if you want to repair your servo you need is to disassembly it (very unpleasant experience) and make sure that segments are not connected with each other by scratching their borders with a needle's end. I did it with my friend's servo that had such problem and it worked fine. 

Thanks for the info! I will try that. I opened the servo back when I broke it and yeah, very unpleasant to open. 

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2 hours ago, IA creations said:

Why don't you use 1M motor with the mini return to center system by @LXF ?

Can you send me a link for the solution? Thanks

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23 hours ago, LXF said:

Thermal protection will kick in before you can damage your motor like that

The servo will actually stop trying to rotate after a couple of seconds of being stopped - and will hold that position until it receives a different single/command.

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Any solution that stalls the motor will cause wear, and also will consume a lot of power - which can slow other motors.

@TomasHubik, have you considered my solution above?  

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On 16/06/2017 at 10:05 AM, LXF said:

Thermal protection will kick in before you can damage your motor like that, but unless it is a limited space solution I would gear it down for being safe with crappy servos

They have upgraded them now, they are stronger and quieter then they used to be, I got a new servo recently and it's much quieter and stronger.

23 hours ago, mocbuild101 said:

The servo will actually stop trying to rotate after a couple of seconds of being stopped - and will hold that position until it receives a different single/command.

Yes

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