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Author Topic: Servo modificacion question  (Read 4260 times)

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Offline IceEarthTopic starter

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Servo modificacion question
« on: April 18, 2008, 01:53:15 AM »
Hi everyone
I followed instruccions about moding my servo futaba S128 and it effectively rotates continuosly but I cant gain control over the velocity at which it turns... I send different pulse widths at high but the speed remains the same... the only time I can mod the velocity is when I change the low pulse widths... but I dont think this is the way it should work. Ill apreciate any positive feedback thanks.

Offline Trumpkin

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Re: Servo modificacion question
« Reply #1 on: April 18, 2008, 08:08:57 AM »
Did you turn the potentiometer until the servo stopped? Are using an R/C setup? If so mess around with the controls on the transmitter. Are you sure it is modifyable?
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Offline superchiku

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Re: Servo modificacion question
« Reply #2 on: April 18, 2008, 11:31:05 AM »
you dfinitely got problems with the potentiometer , check the internal gears again and see if they are sticking well or not
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Offline Rebelgium

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Re: Servo modificacion question
« Reply #3 on: April 18, 2008, 12:46:27 PM »
check the internal gears again and see if they are sticking well or not

What do you mean with that?
There's no problem with the gears, the TS already mentioned the servo rotates OK.
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Offline superchiku

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Re: Servo modificacion question
« Reply #4 on: April 18, 2008, 12:57:19 PM »
sometimes it happens like that , i had this servo once which had a certain kinda loose connection although the potentiometer wasnt set correct still the servo used to rotate continuously after correcting that but once i used glue on the gears again , it worked perfectly
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Offline IceEarthTopic starter

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Re: Servo modificacion question
« Reply #5 on: April 19, 2008, 08:48:19 PM »
I followed all instructions and Im pretty sure that the potentiometer is working properly in fact I had that doubt and modded another one at a different position (not 0 degrees) and obtained the same result. So far all I can do is make go forward or backward but not regulate velocity. Trumpkin I do not know what a R/C setup is... its probably that then. could you plz explain it to me?... thanks for all the feedback guys Im kinda new at this and in my country one of the first to get into all this... thanks

Offline JAy1st

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Re: Servo modificacion question
« Reply #6 on: April 20, 2008, 05:38:33 AM »
I do not think you can control the speed of a servo, modded or not......
It depends on it's characteristics only, the given angular speed.

Anyway when a servo is modded to rotates continuously there is no more pot, only 2 resistors, so what's that story about the pot ???

Am I correct ?

Offline superchiku

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Re: Servo modificacion question
« Reply #7 on: April 20, 2008, 07:06:42 AM »

Quote
I do not think you can control the speed of a servo, modded or not......

no..

when u modify the servo , you lose the position control mechanism of the servo but you gain the velocity control mechanism.. so when you give different pulse widths , u can make it move at different speeds
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Offline JAy1st

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Re: Servo modificacion question
« Reply #8 on: April 20, 2008, 03:14:22 PM »
Quote
when u modify the servo , you lose the position control mechanism of the servo but you gain the velocity control mechanism.. so when you give different pulse widths , u can make it move at different speeds

Good to know, but does it not depend on the type of servo as well ???

Offline superchiku

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Re: Servo modificacion question
« Reply #9 on: April 21, 2008, 11:51:09 AM »
i think its same for all servos coz the internal wiring and the mechanics are similar for all servos
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Offline pomprocker

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Re: Servo modificacion question
« Reply #10 on: April 21, 2008, 11:57:40 AM »
If you're unsure about the potentiometer in the servo, you can always follow airman00's modify servo tutorial on this site under member pages.

He replaces the pot with a resister.

Offline airman00

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Re: Servo modificacion question
« Reply #11 on: April 21, 2008, 08:21:42 PM »
If you're unsure about the potentiometer in the servo, you can always follow airman00's modify servo tutorial on this site under member pages.

He replaces the pot with a resister.

http://www.societyofrobots.com/member_tutorials/node/82
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Offline Admin

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Re: Servo modificacion question
« Reply #12 on: April 26, 2008, 04:55:46 PM »
Quote
Quote
I do not think you can control the speed of a servo, modded or not......
when u modify the servo , you lose the position control mechanism of the servo but you gain the velocity control mechanism..
With a hitec servo you still have speed control after modification, but I've heard parallax servos only have one fixed speed (unverified) . . .

Anyway, I suspect the problem is the signal you are sending is improperly timed. If a servo gets an improper signal, it can often just go at one fixed speed/direction. Have an oscilloscope? How are you controlling the servo?

Offline airman00

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Re: Servo modificacion question
« Reply #13 on: April 27, 2008, 06:49:05 PM »
I've heard that too about parallax servos . anyone have any written documentation online which verifies it
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