Author Topic: Servo Confused.. :'(  (Read 1811 times)

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Offline Joesavage1Topic starter

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Servo Confused.. :'(
« on: February 26, 2009, 12:33:27 PM »
hey, im confused about the servo's, if the pot head is the big plastic bit that moves all the gears round, why superglue it? because then wouldnt the whole thing not be able to move and be completely pointless??


Thanks In Advance


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Offline SmAsH

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Re: Servo Confused.. :'(
« Reply #1 on: February 26, 2009, 01:20:06 PM »
hehe lol pothead... but seriously, if i understand correctly you have to center the servo, glue the pothead down then cut the stop off. the reason we glue the pothead down is so the servo 'thinks' is at the center thus instead of going to an angled it just rotates in a direction.
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Offline HDL_CinC_Dragon

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Re: Servo Confused.. :'(
« Reply #2 on: February 26, 2009, 03:18:46 PM »
The potentiometer is used by the servo to let it know what direction the servo is currently facing. When the servo is zeroed, It is currently in the center of its range of movement. When you send a command to the servo, it will continue to rotate in the direction towards that angle until the pot says "Hey, were there!" and stops the motor from spinning in the servo. Now when you center the servo and glue it down, the potentiometer will constantly say "Were in the center!" The reason you need to cut the head off (I drilled out the plastic gear rather than cut the potentiometer) is so that the gear doesnt keep trying to turn the pot even though it cant move anymore.

Now when youre all finished. If you send it a command to go to 45, it will keep turning and turning and turning until the pot says "Ok were here!" but it instead keeps saying "Were still in the center.... still in the center.... nope, still here!"

Get it now? :)
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Offline Razor Concepts

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Re: Servo Confused.. :'(
« Reply #3 on: February 26, 2009, 04:14:39 PM »
The reason you need to cut the head off (I drilled out the plastic gear rather than cut the potentiometer) is so that the gear doesnt keep trying to turn the pot even though it cant move anymore.
I also do that (drilling out the gear), a lot easier and works just as great. Also some servos actually may have a removeable insert that you could just pop out instead of drilling it out.

Offline HDL_CinC_Dragon

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Re: Servo Confused.. :'(
« Reply #4 on: February 26, 2009, 04:55:51 PM »
I think the removable insert is only found in the slightly more expensive servos :-\
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Offline Joesavage1Topic starter

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Re: Servo Confused.. :'(
« Reply #5 on: February 27, 2009, 01:08:31 AM »
I sorta get what your saying but doesnt the thing your glueing down not the motor thing that moves the whole server? (i assume it is as when u move everything it moves) so how would the serveo be any use electronicaly if its glued?

Offline householdutensils

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Re: Servo Confused.. :'(
« Reply #6 on: February 27, 2009, 01:17:25 AM »
As said above, the pot measures the servos rotation. There is a DC Motor that actually makes it tall go round.
« Last Edit: February 27, 2009, 01:18:27 AM by householdutensils »

Offline Joesavage1Topic starter

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Re: Servo Confused.. :'(
« Reply #7 on: February 27, 2009, 09:30:06 AM »
Ohh.. so this way just basicly makes the pot break.

Thanks 4 the help.



Joe

Offline HDL_CinC_Dragon

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Re: Servo Confused.. :'(
« Reply #8 on: February 27, 2009, 02:27:55 PM »
no no lol. It doesnt make the pot break! The pot is still functional. It is just tricked into always thinking its in the center which means the servo will always think its in the center which means when its told to go to a direction, it will just continuously rotate until it reaches that direction which it never will.
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Offline Webbot

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Re: Servo Confused.. :'(
« Reply #9 on: February 27, 2009, 09:22:12 PM »
hey, im confused about the servo's, if the pot head is the big plastic bit that moves all the gears round, why superglue it? because then wouldnt the whole thing not be able to move and be completely pointless??

Open your servo and you will find lots of gears. One of them has a slot on the bottom and sits on a potentiometer. This makes up the encoder. The servo knows where it currently is due to the pot position. So it starts to move the motor via  the gears - including the gear that sits on the pot. So now the servo has a new 'actual' position of the servo.

The pot gives 'current position' but is changed as the gears move to help home in on the required position.

When you modify the servo you 'dremmel' out the slot so that the gear moves without changing the pot. And it is the pot that is superglued in place to stop it moving. Having done this then when you tell the servo to go 'slightly' clockwise it says ok 'thats a smalll movement' so I will start turning the motor until the pot says I've got there. But since the pot is glued in place it doesn't move so the servo keeps thinking 'thats a small movement' so the output shaft keeps moving clockwise. If you telll it to make a large movement (eg full clockwise) then it says 'hey - a big movement' so it moves  the motor quickly. But since the glued pot says nothing has changed then it keeps saying this so the shaft continues to move quickly

You aren't glueing the gears, you are only glueing the pot, to make the servo think it has never got to the correct place so that it keeps turning.

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Offline Joesavage1Topic starter

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Re: Servo Confused.. :'(
« Reply #10 on: February 28, 2009, 01:09:04 AM »
Oh.. ok gotcha.

Thanks Guys!



Joe

 


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