full 360 servo

kelvin james

In case anybody has not seen these, this is a 360 degree standard servo, it would be good for panning sensors and cams.









www.acroname.com/robotics/parts/R298-1T-SERVO.html

Bruce Bates

Kelvin -

Just based on the design of the servo horn and the 360 degree claim, I suspect that's nothing more than a winch servo. If that's the case, it ought to be able to rotate somewhere in the following range, depending on the manufacturer:

2.5 * 360 ==> 3.0 * 360 or 2 1/2 to 3 turns in total

Regards,

Bruce Bates

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There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!

kelvin james

Definately a winch servo, they come in 1/2 turn 180 degree, full turn 360 degree, or this one like Bruce mentioned 3 1/2 turns but becomes 1260 degree. Probably just some inner gear reduction to accomplish this.




www.servocity.com/html/hs-785hb_3_5_rotations.html

Lawson

Heh, good timing finding this! I got hit by a project-bug that would work best with a servo that can do 180deg using a standard RC radio. Other sail winch servos could do it, but this one is smaller, and has less "wasted" range of motion. BTW, this looks like a GWS S125 1T

Marty

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Lunch cures all problems! have you had lunch?

JamieT

Hello,

I was looking at buying this exact servo because the one that came with my basic stamp kit only goes from 10 o'clock to 2 o'clock, but I need one that will go to, say the 7 or 8 o'clock position. Does anyone know if a 360 servo will go to this position? I'm also confused because my standard futaba servo claims to rotate 180 degrees, but going from 10 o'clock to 2 o'clock is only about 120 degrees. Am I missing out on something?

Bruce Bates

Jamie -

First, what position an R/C servo rotates to is highly dependent on three things:

1. The width of the timing pulse sent to it,

2. Whether an appropriate follow-up pause is issued,

and

3. How often the pulse is repeated.

If any one of those items is missing or incorrect, the servo may reach a position you don't intend for it to reach. Here is a brief example, part of a program, which shows how one should write a program to exercise the servo, showing its full range of motion. This example is written for use on a Stamp BS-2. It rotates the servo in one direction, and then rotates it again in the opposite direction:

Servo_pin CON 0 'I/O pin that is connected to servo
temp VAR Word 'Work space for FOR NEXT

start:

FOR temp = 200 TO 1200
PULSOUT Servo_pin,temp
PAUSE 50
NEXT

FOR temp = 1200 TO 200
PULSOUT Servo_pin,temp
PAUSE 50
NEXT

GOTO start

I rather doubt that a continuous rotation servo is really what you want. It's much more likely that you want a servo which has limit stops. A continuous rotation servo has the limit stops removed; thus it can rotate like an ordinary DC motor - continuously.

The range of travel will also be different, based on the particular model of the servo you purchase from any given manufacturer. The servos Parallax sell are made by Futaba. If yours is like the standard rotation servo that Parallax sells, it will operate no differently than the one you now have. That servo has a range of 0 to 180 degrees, as can be seen in the documentation provided. The documentation can be found on the page where the servo can be purchased on the Parallax web site.

Last, there are servos whose range exceeds 180 degrees. In fact, it can exceed 360 degrees. These are known as "winch" servos, since they're often used on R/C model sail boats for pulling up the anchor chain, but they have many other uses. Some of them can make 3 FULL rotations.

Probably more than you wanted to know, but there you have it.

Regards,

Bruce Bates

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Programming can't be all that difficult, it's nothing but 1's and 0's

JamieT

Thank you for the information.
I do currently have the futaba standard servo that parallax sells. Based on what the manual says, its min and max pulsout durations are 500 and 1000, where the 500 will put it at the 10 o'clock position, the 1000 duration will put it at the 2 o'clock position, and in between, 750 will put it at 12 o'clock. It won't seem to let it go beyond those positions. I guess that I will need the full 360 servo but am worried that it won't work with the basic stamp microcontroller. Do you know if there's anything in particular that I should avoid, such as high current or voltage requirements?

Thanks.

Bruce Bates

Jamie -

I'm not sure which "manual" you're reading, but the manual which is appropriate for the Parallax Standard Servo (as found on thier web site) says the following on the first page of that document:

"The Parallax standard servo is ideal for robotics and basic movement projects. These servos will allow a movement range of 0 to 180 degrees. The Parallax servo output gear shaft is a standard Futaba configuration. The servo is manufactured by Futaba specifically for Parallax. "

You can go from there.

Regards,

Bruce Bates

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Programming can't be all that difficult, it's nothing but 1's and 0's