I got a GWS mini servo motor. Has any one got the data for this motor?

 

Try using google before asking questions in the forum, the following link took less than 5 seconds to find by searching for "GWS mini servo"

http://www.pololu.com/products/servos.html

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I have been to that site and many other sites before. But I need to know the pulse width range and frame rate, which I couldn't find. Usually they are between 1 to 2 ms. But it's not always the case. I also need to know the range of angle. I just thought someone out there might have experience with this motor. May be I have to assume the usual specs.

 

Yes, it drives at 1ms-2ms.

http://www.gws.com.tw/english/product/servo/mini.htm

 

yes, assume the usual specs and then experiment with it. There is a pretty wide range for hobby servos - even between 2 units with the same model number. I have a several GWS servos (different model number) converted to full rotation and I had to adjust the pulse length to each motor to get them to run at the same speed.

 

You are so right.
May be that's why they don't have that part of specs, the tolerance is too wide. May be that's why it's cheap.

 

I don't see the problem?, as servos (which they are designed as), they presumably work perfectly?, by modifying them to use just as motors there's no longer any feedback, so I see no reason to assume that they should work identically.

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I think they should provide specs with tolerance. It's important to use the servo motor for positioning.
It the pulse width is 1ms to 2 ms for example, you'll expect at 1.5ms it's in mid position. At 1 ms or 2 ms it's on both end stops. If it's outside this range the motor will keep hitting the end stops and wears out the motor.
If you experiment it for best result and you think you got the specs right and buy 100 more identical motors, if every one is different for a wide range, you'll waste so much time just because the manufacturer don't adhere to their product spec.

 

Any 'end stops' are way outside the normal operating range, the pot will turn 270 degrees, the operating range is probably only 45 degrees or so?. Servos generally can be fed a much wider range than the 1-2mS they are specified for, and will rotate correspondingly further.

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Actually, Nigel, the feedback is also off on the GWSs. At least the cheaper line. I think it's also the case for most servos. The reason why it doesn't matter is that in the intended application (RC vehicles) the user adjusts the pulse width via joy stick. Thus, the "pilot" compensates for the gross inaccuracy of the servos.

They aren't used much in tandem except for robot drive like the common sumobot. Calibration/compensation is pretty easy to do so robot builders accept the problem as a minor annoyance to have cheap, compact, easy to interface motors.

 

Big model aircraft (like these: http://www.cactusaviation.com/Galler.../hamilton.html) also use multiple servos on the same flight surface. A variety of servo balancers are available. For example, here is just one version:

http://www.servocity.com/html/servo_synchronizer.html

Besides the need to balance and match servos that are in tandem, one must also consider drift. Some servos, even the expensive ones, drift terribly with temperature. Thus, the match can change from day to day. John

 

wow, that is one big mofo model - any bigger and the FAA is going to come calling. I'm surprised how relatively cheap that balancer is.

 

There is definitely a gray zone. The biggest model I have seen was a 25% scale B29. It weighed 300#, had a 30+ foot wing and required two pilots (just like the original). Other 33% to 50% scale models of smaller aircraft are becoming more common. The FAA is concerned, and there are now limits on altitude (I believe it is 500 ft) at which such models can fly without a waiver. Look at the HP of some of the engines at the Desert Aviation link. They exceed ultralights. John