Author Topic: need urgent help with servo mod  (Read 19050 times)

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Offline annoyin_kidTopic starter

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need urgent help with servo mod
« on: January 23, 2007, 11:03:22 PM »
so here i am happily modifying my first servo when i come across a problem and start panicking. the main gear of my futaba s3003 has the pot turning thing as part of it. the pot turner was made as part of the main gear and there is no way i can pull it out. what do i do now?

i put everything back together and it works like it used to.
« Last Edit: January 23, 2007, 11:23:32 PM by annoyin_kid »

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Re: need urgent help with servo mod
« Reply #1 on: January 24, 2007, 07:57:11 AM »
can you post a picture?

two thoughts come to mind . . . maybe drill out a hole through the center of the main gear, or get a pair of wire cutters and cut off the head of the pot (make sure you center it first).

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #2 on: January 24, 2007, 12:07:01 PM »
i used my mad photoshop skills and drew this picture of what the gear looked like from the bottom

would this way of modding the servo work?
http://www.ranchbots.com/club/papers/Modifying%20Hobby%20Servo%20Motors%20for%20Continuous%20Rotation.pdf

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Re: need urgent help with servo mod
« Reply #3 on: January 24, 2007, 12:32:55 PM »
eehhhhh so the method in that link is unneccessarily overcomplicated.

he is not only modding the gears, but also swapping out the pot for resistors. you dont need to swap out the pot. just either remove the green or the red so it can rotate freely.

you could drill out a hole through the center of the gear, or get a pair of wire cutters and cut off the head of the pot. basically follow my method of modifying a servo:
http://www.societyofrobots.com/actuators_modifyservo.shtml

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #4 on: January 24, 2007, 12:51:59 PM »
yea the other way is a bit complicated but if i ever need to go back to having a normal servo i can but if i decide to cut off the pot head i cant go back to original condition. (im on a tight budget or other wise i wouldn't care)

do you have any idea if that complicated way will work?
« Last Edit: January 24, 2007, 12:56:11 PM by annoyin_kid »

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Re: need urgent help with servo mod
« Reply #5 on: January 24, 2007, 12:59:17 PM »
To my knowledge there are no servos with plastic gears that allow you to un-modify an already modified servo. Once its modified, there is no going back. You must still snip a flange (the mechanical stop) off the gear, even if the pot is removed. There is no advantage to that complicated way :P

The best you can do is drill/scrape the red stuff out, and if you want to un-modify the servo later, just buy a gear replacement set (much cheaper than a new servo).

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #6 on: January 24, 2007, 01:05:33 PM »
oh i never knew there was such a thing as a gear replacement set!!! well thanks for saving me from buying a new soldering iron and all the other unnecessary stuff to do that mod :) :) :)

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Re: need urgent help with servo mod
« Reply #7 on: January 24, 2007, 02:50:01 PM »
just in case . . .

Futaba Servo Gear Set S3003/S3004

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXH422&P=M

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #8 on: January 24, 2007, 03:16:34 PM »
wot the hell the gears are like half the price of the servo itself!!!!!!!!!

update: the servo mod was successful thanks for all the help man, you are the best.
just one question you know the bit where you gotta glue the pot head - it is actually unnecessary. why would you bother holding it in place when there is nothing that is going to move it any way?
« Last Edit: January 24, 2007, 04:22:49 PM by annoyin_kid »

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #9 on: January 24, 2007, 05:22:53 PM »
what are the maximum and minimum pulse widths for modded servo? are they 0.75 ms and 2.25 ms and what would happen to the servo if i go out of the max/min limit?

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Re: need urgent help with servo mod
« Reply #10 on: January 24, 2007, 08:46:00 PM »
Quote
just one question you know the bit where you gotta glue the pot head - it is actually unnecessary. why would you bother holding it in place when there is nothing that is going to move it any way?

Ive had this happen on two occasions where the pot head slightly shifted itself, messing up the servo centering. This is because the pot head is extremely sensitive to even vibration. Considering Ive used servos a billion times already its pretty rare, but possible. A small dab of glue cant hurt, and if you want to remove it, you could always dissolved the glue later with like acetyl alcohol . . . But even then, if it does happen, you could just simply tweak your code or reopen up the servo to fix it . . .

Quote
what are the maximum and minimum pulse widths for modded servo?

this is different for almost every servo type, and even sometimes varies within the same type of servo. usually its between 1ms and 1.8ms. to find out, i just run a test program that slowly ramps up the servo speed while outputting the speed value to my laptop with hyperterminal. when the servo stops changing speed, thats when its reached the maximum. most of the time tho im just too lazy and guess until its satisfactory.

Quote
what would happen to the servo if i go out of the max/min limit

nothing bad would happen to the servo . . . usually it would just lock/freeze up at some value. depends on the servo, if its an analog type or digital type, etc.

Offline annoyin_kidTopic starter

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Re: need urgent help with servo mod
« Reply #11 on: January 24, 2007, 10:13:11 PM »
awesome thanks man  8) 8) 8)

Offline jka

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Re: need urgent help with servo mod
« Reply #12 on: May 28, 2008, 02:55:23 AM »
To my knowledge there are no servos with plastic gears that allow you to un-modify an already modified servo. Once its modified, there is no going back. You must still snip a flange (the mechanical stop) off the gear, even if the pot is removed. There is no advantage to that complicated way :P

But would you actually need the mechanical stop? If you put the pot back it should work as a normal servo as long as you keep the pulse widths within the spec limits.

Offline malex

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Re: need urgent help with servo mod
« Reply #13 on: June 04, 2008, 10:18:40 PM »
Can't you just cut off the head of the pot and then you wont have to remove the slot in the gear?  Then i suppose you can glue the remains into place. 


Offline Rebelgium

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Re: need urgent help with servo mod
« Reply #14 on: June 05, 2008, 03:38:15 AM »
Can't you just cut off the head of the pot and then you wont have to remove the slot in the gear?  Then i suppose you can glue the remains into place. 



No, the mechanical stop needs to be removed to.
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Offline malex

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Re: need urgent help with servo mod
« Reply #15 on: June 05, 2008, 11:56:34 AM »
I know, I got rid of the mechanical stop, but for the step where you have to remove the slot inside the gear that attaches it to the pot, can you simply cut off the head of the pot instead of gouging the inside of the gear?  my gear doesn't have a removable interior.

Offline bukowski

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Re: need urgent help with servo mod
« Reply #16 on: June 05, 2008, 01:10:26 PM »
yep.

 


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