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MrK

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Posts: 3
Reply with quote  #1 
I searched and never saw an answer. 

What is the "spec" starting point for the servos in competition? All 4 of my servos stop at 40 degrees. Surely they are allowed at least 180 degrees, and most servos can be spec'd to rotation continuously.

Thank you!
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dmgauntt

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Reply with quote  #2 
The Futaba servos have hard stops approximately 120 degrees apart, but the range of rotation you an achieve through the software is approximately 90 degrees (-45 deg to +45deg).

Other specs for the Futaba S3003 servos can be found online at http://www.futabarc.com/servos/analog.html and at http://www.gpdealera.com/cgi-bin/wgainf100p.pgm?I=FUTM0031.  Unfortunately, they do not spec out the rotation range.
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MrK

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Reply with quote  #3 
Dm, thank you for your reply.

So if mine are hard stopping at less than 50 total degrees... are they defective or has someone modified them?


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jgraber

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Posts: 184
Reply with quote  #4 
I have never seen a servo in the condition you describe.

Are they the right servos:  do they have 3003 or 3004 printed on the case?  

Servos can easily be overstressed and break the tiny plastic gears inside, which makes the gear noise irregular when rotating by hand.
But I've never seen broken gears affect the hard stop.

It is more likely that we have different definitions of 'hard stop' and  "50 total degrees".

Here is my definition and my procedure to measure it.  
With servo unplugged and a servo horn with only one arm,
- hand rotate clockwise until it hard stops, remove servo horn
- position the servo face up, with wire pointed toward you
- press fit on the servo horn with arm pointing to the right, now it is at 0 degrees like a protractor.
- hand rotate the servo horn counterclockwise until it hard stops
- My expectation is that the arm is left of straight up, which means > 90 degrees between hard stops.
  Your "50 total degrees" report would mean that the horn point is to the right of straight up.

What do you find when following my procedure?
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MrK

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Reply with quote  #5 
I have the 3003 Futuba servos.

I hand turned them, they go to about 180 total degrees. I then take them to center... and hook them up. They only go to about 25 degrees left, 25 degrees right, for the total of 50 or so degrees.

Thank you for your help, it seems to still have issues.
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jgraber

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Reply with quote  #6 
Great.  OK, so it is not the hard stop, it is the command sending limitation.
What are you programming with (pros,EasyC,RobotC,Simulink)?  and what value are you programming it to?  
Sending command speed of  -127 and +127 should get you -45 to +45, for a total of about 90 degrees.
The other thing to check when using servos, is what happens when you lose communications.
Possible results:  A go idle with no back force resistance,  B freeze in place with back force resistance,  C go to zero position.

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