Go to Post I have learned so much from this program and am forever changed by FIRST and its community. You have made me a better person in so many ways. Thank you. - Jessica Boucher [more]
Home
Go Back   Chief Delphi > Technical > Motors
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 04-02-2004, 16:56
tml240's Avatar
tml240 tml240 is offline
bahh
no team
Team Role: Alumni
 
Join Date: Jan 2004
Rookie Year: 2003
Location: Ann Arbor, MI
Posts: 63
tml240 is on a distinguished road
How do the servos work?

our team was wondering how the servo works
i searched and cant find the threads...

thing we need is we want to turn the servo backwards after the servo makes full rotation

our program in Turing doesnt seem to work either...
__________________

OHL 2004- ultimate NHL 2004 MOD

Last edited by tml240 : 04-02-2004 at 17:28.
  #2   Spotlight this post!  
Unread 04-02-2004, 18:03
Kris Verdeyen's Avatar
Kris Verdeyen Kris Verdeyen is offline
LSR Emcee/Alamo Game Announcer
FRC #0118 (Robonauts)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 2001
Location: Houston, TX
Posts: 699
Kris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond reputeKris Verdeyen has a reputation beyond repute
Re: How do the servos work?

Quote:
Originally Posted by tml240
our team was wondering how the servo works
i searched and cant find the threads...

thing we need is we want to turn the servo backwards after the servo makes full rotation

our program in Turing doesnt seem to work either...
The main problem you have is that hobby servos won't make a full rotation. They tend to be limited to around 180 degrees, and have no internal feedback to allow you to know when they've reached their holding point, so you'd need an external limit switch to feed that back, and let the code know when to reverse.
__________________
...Only a few people are awake and they live in a state of constant total amazement. -JP Shanley, Joe vs. the Volcano
  #3   Spotlight this post!  
Unread 04-02-2004, 18:14
zainali's Avatar
zainali zainali is offline
Registered User
AKA: Syed Zain Ali
#1241 (Theory 6)
Team Role: Engineer
 
Join Date: Feb 2004
Location: Mississauga
Posts: 19
zainali is an unknown quantity at this point
Question Re: How do the servos work?

Quote:
Originally Posted by Kris Verdeyen
The main problem you have is that hobby servos won't make a full rotation. They tend to be limited to around 180 degrees, and have no internal feedback to allow you to know when they've reached their holding point, so you'd need an external limit switch to feed that back, and let the code know when to reverse.
We don't want the servo to rotate more then it is doing right now.But we were wondering if servos can be made to rotate backwards. This is because everytime you make it turn you have to manually twist it back to its starting position to make it turn again.

So can the servos actually be made to move backward, if so what type of signal or the code should you use.

As far as what i have researched and what you just said about their limit of 180 degrees matching, and the only way to modify would to be to take it apart and modify it internally ?? right..

your help is appreciated, this is my first year on the competition so do forgive me if these are newbie questions

thanks
  #4   Spotlight this post!  
Unread 04-02-2004, 18:30
Mike Soukup's Avatar
Mike Soukup Mike Soukup is offline
Software guy
FRC #0111 (Wildstang)
Team Role: Engineer
 
Join Date: May 2001
Rookie Year: 1996
Location: Schaumburg, IL
Posts: 797
Mike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond reputeMike Soukup has a reputation beyond repute
Re: How do the servos work?

Quote:
Originally Posted by zainali
We don't want the servo to rotate more then it is doing right now.But we were wondering if servos can be made to rotate backwards. This is because everytime you make it turn you have to manually twist it back to its starting position to make it turn again.
I think you first need to understand how a servo behaves. Unlike a motor, you do not give a servo a speed, you give it a position. If you directly map a motor to the y-axis of a joystick and push the stick half way forward, the motor will run at half speed until you release the stick, then it will stop. If you do the same with a servo, it will rotate half way to one end and stay there, then when you release the stick it will return to the middle. The servo is actually a motor and a potentiometer all in one, it performs the whole feedback loop for you. You give the servo a position (from 0-255) and it goes to that position and stays there until you give it a new position. They're actually pretty cool little devices.
  #5   Spotlight this post!  
Unread 04-02-2004, 18:35
zainali's Avatar
zainali zainali is offline
Registered User
AKA: Syed Zain Ali
#1241 (Theory 6)
Team Role: Engineer
 
Join Date: Feb 2004
Location: Mississauga
Posts: 19
zainali is an unknown quantity at this point
Re: How do the servos work?

Quote:
Originally Posted by Mike Soukup
I think you first need to understand how a servo behaves. Unlike a motor, you do not give a servo a speed, you give it a position. If you directly map a motor to the y-axis of a joystick and push the stick half way forward, the motor will run at half speed until you release the stick, then it will stop. If you do the same with a servo, it will rotate half way to one end and stay there, then when you release the stick it will return to the middle. The servo is actually a motor and a potentiometer all in one, it performs the whole feedback loop for you. You give the servo a position (from 0-255) and it goes to that position and stays there until you give it a new position. They're actually pretty cool little devices.
so how would i make it come back, well we were just testing the sevo using Turing We made it output 1 with a small delay and looped it.

So how would i make it come back???? we tried to output 0 but it doesn't come back any ideas???
__________________
Rick Hansen Secondary School
Team 1241
www.Theory6.org

GO LEAFS GO
  #6   Spotlight this post!  
Unread 04-02-2004, 19:07
steven114 steven114 is offline
Programming Wizard and Team Captain
AKA: Steven Schlansker
FRC #0114 (Eaglestrike)
Team Role: Programmer
 
Join Date: Feb 2004
Location: Los Altos, CA
Posts: 335
steven114 is a jewel in the roughsteven114 is a jewel in the roughsteven114 is a jewel in the rough
Send a message via AIM to steven114
Re: How do the servos work?

127 is the center, not 0. 0-126 is one direction, and 128-254 is the other direction from the center.
  #7   Spotlight this post!  
Unread 07-02-2004, 01:01
deltacoder1020's Avatar
deltacoder1020 deltacoder1020 is offline
Computer Guy
AKA: Dav
#1020 (The Indiana Prank Monkeys)
Team Role: Programmer
 
Join Date: Jan 2004
Location: Muncie, Indiana
Posts: 340
deltacoder1020 has a spectacular aura aboutdeltacoder1020 has a spectacular aura about
Send a message via AIM to deltacoder1020
Re: How do the servos work?

essentially, when you output 1, you told the servo to rotate almost as far as it can in one direction (almost, because the minimum is 0, but there's little difference). thus, outputting 0 wouldn't make it come back, only turn a fraction more in the direction it already was.

dead center would be outputting 127. try that.

likewise, to make it turn in fully the other direction, output something towards the upper end of the range, such as 254.
__________________
Team 1020, the Indiana Prank Monkeys (www.team1020.org)
  #8   Spotlight this post!  
Unread 07-02-2004, 12:46
tml240's Avatar
tml240 tml240 is offline
bahh
no team
Team Role: Alumni
 
Join Date: Jan 2004
Rookie Year: 2003
Location: Ann Arbor, MI
Posts: 63
tml240 is on a distinguished road
Re: How do the servos work?

are the servos in digital or analogue?
__________________

OHL 2004- ultimate NHL 2004 MOD
  #9   Spotlight this post!  
Unread 07-02-2004, 22:28
steven114 steven114 is offline
Programming Wizard and Team Captain
AKA: Steven Schlansker
FRC #0114 (Eaglestrike)
Team Role: Programmer
 
Join Date: Feb 2004
Location: Los Altos, CA
Posts: 335
steven114 is a jewel in the roughsteven114 is a jewel in the roughsteven114 is a jewel in the rough
Send a message via AIM to steven114
Re: How do the servos work?

Well, considering that they vary from 0-255, they are considered analog. But, a more useful answer might be proposed if you explain more about what you want to know... (e.g. why does it matter?)
  #10   Spotlight this post!  
Unread 09-02-2004, 15:57
Justin Stiltner's Avatar
Justin Stiltner Justin Stiltner is offline
The big guy
no team
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 2000
Location: Blacksburg, Va.
Posts: 305
Justin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud ofJustin Stiltner has much to be proud of
Send a message via ICQ to Justin Stiltner Send a message via AIM to Justin Stiltner Send a message via MSN to Justin Stiltner Send a message via Yahoo to Justin Stiltner
Re: How do the servos work?

You might want to think of it this way, output the data to the servo just like you do with a speed controller, ie if you want to center it send 127, full reverse 0 and full foward is 255. however insted of full foward and reverse you would have fully clockwise and fully counter clockwise. As somebody else suggested, map the data from an joystick to the servo output and print the data to your laptop and you will see what we are talking about.
__________________
Justin Stiltner
Lead Robot Inspector, VCU Regional
Unmanned Systems Lab, Virginia Tech
KI4URQ
  #11   Spotlight this post!  
Unread 09-02-2004, 17:26
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,798
Al Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond repute
Re: How do the servos work?

Quote:
Originally Posted by tml240
are the servos in digital or analogue?
The true answer here is both. The PWM data represents a particular angular position. The output shaft of the servo has a pot connected to it that outputs an analog voltage relative to the position. The circuit inside the servo then compares the position it was told to go to and the position it is currently at and sends a signal to the motor to move. When the output shaft/pot are at the position the PWM signal wants it to be the motor is shut off. This type of positioning is very common and can be accomplished fully digital, fully analog (this is the way it was done before the advent of cheap micros and memory modules) or a combination of both. The final design is one in which the tradeoffs between accuracy and expense have resulted in a fairly repeatable little box that costs under $50.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
  #12   Spotlight this post!  
Unread 09-02-2004, 19:12
steven114 steven114 is offline
Programming Wizard and Team Captain
AKA: Steven Schlansker
FRC #0114 (Eaglestrike)
Team Role: Programmer
 
Join Date: Feb 2004
Location: Los Altos, CA
Posts: 335
steven114 is a jewel in the roughsteven114 is a jewel in the roughsteven114 is a jewel in the rough
Send a message via AIM to steven114
Re: How do the servos work?

Ah, whoops. I was talking about the input signal, not how it worked...
  #13   Spotlight this post!  
Unread 11-02-2004, 20:51
Phil_Lutz's Avatar
Phil_Lutz Phil_Lutz is offline
Phil Lutz
#0851 (Froggers)
Team Role: Mentor
 
Join Date: Jan 2004
Location: El Segundo, CA
Posts: 67
Phil_Lutz is on a distinguished road
Send a message via Yahoo to Phil_Lutz
Unhappy Re: How do the servos work?

I have a tangent problem to this that I need a solution too.
I have the Servo directly connected to the PWM1 jack on the robot.

I map the PWM to a variable and set the variable to 0.
I tell the program to change the servo position (increment) when the trigger is held.

Nothing happens.
We are printf ' ingf the PWM value and the code seems to be working but the servo never moves.

Help!

Thanks,

Phil
  #14   Spotlight this post!  
Unread 11-02-2004, 20:54
Rhs953's Avatar
Rhs953 Rhs953 is offline
Revenge is near...
AKA: Mike
#0953 (Illumanati)
Team Role: Engineer
 
Join Date: Jan 2004
Location: Reno
Posts: 99
Rhs953 has a little shameless behaviour in the past
Send a message via AIM to Rhs953
Re: How do the servos work?

Most servos wont make a full rotation. Servos are used to make small turns like on a model airplane. They are use to raise and lower the wing pich.
__________________
___________________________
If all else fails, use a bigger hammer.
  #15   Spotlight this post!  
Unread 11-02-2004, 20:55
steven114 steven114 is offline
Programming Wizard and Team Captain
AKA: Steven Schlansker
FRC #0114 (Eaglestrike)
Team Role: Programmer
 
Join Date: Feb 2004
Location: Los Altos, CA
Posts: 335
steven114 is a jewel in the roughsteven114 is a jewel in the roughsteven114 is a jewel in the rough
Send a message via AIM to steven114
Re: How do the servos work?

A few common debugging procedures:

1) Ensure that the triple cables from the Servo are in the proper direction

2) Test it with a different servo. Then try a different pin.

3) Post the code here.
Closed Thread


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
using older servos pryoplasm Kit & Additional Hardware 4 24-01-2004 20:22
Problems of the mind... effecting work Gadget470 Chit-Chat 20 18-11-2003 11:56
Need help in creating program to use servo's to shift drive archiver 2001 19 24-06-2002 00:35
Who knows how the motors [I]really[/I] work? Wetzel Chit-Chat 5 13-02-2002 21:50
Does anyone on this board work at home depot? mnkysp6353 General Forum 2 30-12-2001 13:27


All times are GMT -5. The time now is 14:58.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi