Servo Questions

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
GoodSamaritan
Posts: 6
Joined: Thu Jul 22, 2004 1:01 am
Location: Central Ky
Contact:

Servo Questions

Post by GoodSamaritan » Thu Jul 22, 2004 4:59 pm

I posted this in the robotics forum, before I realized it doesnt get much traffic. <p>I have a background in industrial controls, and servo drive systems. However I am new to the hobby variety. <p>I am working on a project that requires a signal from a potentiometer to be converted to X number of degrees of rotation. (opening and closing the throttle on a lagre engine from a safe distance) <p>Does anyone have any information on what is available on the market to accomplish this.
Once again this has to be a hardwired system. RC hobby stuff wont be practical. Thank you.
Bryan.
Just another HiTech Hillbilly

User avatar
Chris Smith
Posts: 4325
Joined: Tue Dec 04, 2001 1:01 am
Location: Bieber Ca.

Re: Servo Questions

Post by Chris Smith » Thu Jul 22, 2004 5:25 pm

I would stick with over the counter [Futaba] RC equipment.

GoodSamaritan
Posts: 6
Joined: Thu Jul 22, 2004 1:01 am
Location: Central Ky
Contact:

Re: Servo Questions

Post by GoodSamaritan » Thu Jul 22, 2004 5:37 pm

My problem is that I need this to be hardwired NOT radio controled. <p>If there is a way to control the Rc hobby stuff via a cable I would be thrilled. This would keep my project way under budget. <p>Once again, I CANNOT USE A RADIO CONTROL for this project. It HAS TO BE HARDWIRED. <p>Thanks
Just another HiTech Hillbilly

toejam
Posts: 253
Joined: Wed Dec 05, 2001 1:01 am
Location: n.c.
Contact:

Re: Servo Questions

Post by toejam » Fri Jul 23, 2004 2:33 am

A length of properly grounded coax would work using Chris's suggestion.

L. Daniel Rosa
Posts: 400
Joined: Tue Dec 25, 2001 1:01 am
Location: Bellingham, WA
Contact:

Re: Servo Questions

Post by L. Daniel Rosa » Fri Jul 23, 2004 5:20 am

HTH, I think that what Chris is saying is that the Futaba line of servos is likely to have one of the torque rating you need. As for the radio v. cable the servo doesn't care, that's an issue for the controller.

Rodney
Posts: 162
Joined: Sat Aug 31, 2002 1:01 am
Location: Titusville, FL USA
Contact:

Re: Servo Questions

Post by Rodney » Fri Jul 23, 2004 8:35 am

Any of the commonly used RC servos could work. They need not be radio controlled. Any three wire system (+4.8 to 6 volts, ground, and signal) will suffice. The signal is just a 1.5 millisecond wide positive going pulse that occurs every 20 to 25 milliseconds--easily provided with a 555 timer chip and a pot. The range is about plus or minus 30 to 45 degrees from neatural with a pulse width of 1 to 2 milliseconds, i.e. one extreme at 1 millisecond pulse width, the other extreme at 2 milliseconds pulse width. Torgue values are available from 15 inch/ounce (the mini servos) to up around 150 to 300 inch/ounces on the larger ones. If you use a sail winch servo, the torgue can be much greater at the expense of speed of rotation.

GoodSamaritan
Posts: 6
Joined: Thu Jul 22, 2004 1:01 am
Location: Central Ky
Contact:

Re: Servo Questions

Post by GoodSamaritan » Sat Jul 24, 2004 10:46 am

Thank you Rodney!!!<p>That is the kind of info I need.
Just another HiTech Hillbilly

Tparker
Posts: 40
Joined: Tue Apr 29, 2003 1:01 am
Contact:

Re: Servo Questions

Post by Tparker » Mon Jul 26, 2004 9:10 am

Some R/C transmitters have a plug that allows you to test/controll the servos bypassing the RF section. This allows you to "adjust" the servo without transmitting a signal.

Lin Farquhar
Posts: 30
Joined: Sun Oct 19, 2003 1:01 am
Location: Western Australia
Contact:

Re: Servo Questions

Post by Lin Farquhar » Wed Aug 11, 2004 9:32 am

check out
rev-ed.co.uk
They supply a range of PicAxe chips which are bootstrapped PICs, programmable in BASIC. Software is a free download with full tutorials. Programming hardware is 2 resistors and a D9 plug out of your serial port. The 'basic BASIC' language includes a 'servo' one-line command for exactly your sort of app.
Rgds, Lin

Will
Posts: 310
Joined: Tue Feb 11, 2003 1:01 am
Location: Katy Texas
Contact:

Re: Servo Questions

Post by Will » Thu Aug 12, 2004 9:37 am

Hi Tek,
I can't really tell whether you want to buy, one of these or make one ? If you want to buy one you could get it a reasonable price from Barber Colman - they could supply you with a standard device which will accept the voltage signal from your potentiometer and also with an electro-mechanical device which will acce-pt the signals from the first device operate the throttle. I think the latter device is current driven - I think you could probably get both devices for less than $200 - I used them years ago and they work very well.
In order for you to tune the device you will need adjustable sensitivity i.e how much output (To throttle) change for how much input change. If you extended to that then you would probably finish up building or buying a PID controller
BB

Post Reply

Who is online

Users browsing this forum: No registered users and 38 guests