Sail Winch programmable

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gradguy1
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Joined: Tue Mar 15, 2011 3:12 pm

Sail Winch programmable

Post by gradguy1 » Tue Mar 15, 2011 3:31 pm

Hello...

This subject has caused a lot of headaches and it's my hope somebody can tell me what to do and what can be done. I'm a grad student working on my masters thesis...I've got a paraglider that's actuated using two analog HS-785HB servos, works great... took me forever to find the right servo with right torque. Those are two major issues.

The problem is that because the sail winch servos are on a continuous loop pulley, setup I can not simply put these two servos on y harness because the servos ranges are beyond the continuous loop pulley's ranges when the opposite servo is actuated. IE the line attachment point just gets sucked into the pulley itself and stalls the servo. To circumvent this problem I have to set up each servo on a separate R/C channel and trim accordingly. This has proved to is a very tricky and difficult.

I would like to be able to get both on the same channel and adjust their ranges accordingly. I haven't seen any digital winch servos with the torque I require. This seems to be my last option.

Can this be done? If so how?
Any info would be very much appreciated.

jharvey
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Post by jharvey » Wed Mar 16, 2011 12:36 am

Sounds like you want a OpenServo with OE. Full rotation, absolute position. Is that what you are looking for?

gradguy1
Posts: 2
Joined: Tue Mar 15, 2011 3:12 pm

Post by gradguy1 » Wed Mar 16, 2011 2:05 am

jharvey wrote:Sounds like you want a OpenServo with OE. Full rotation, absolute position. Is that what you are looking for?
First thanks for the reply... As far as what I am looking for... I'm really new to all of this but " i think so"

The stock HS-785HB servos I have put out 3.5 rotations so I guess full rotation would be a yes. IE "all the rotation it comes with"

I'm not sure on absolute position... what does that mean?

What is "OE"? a software?

And again thanks for the reply

jharvey
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Posts: 362
Joined: Sun Mar 15, 2009 12:06 pm
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Post by jharvey » Wed Mar 16, 2011 9:39 am

OE is Open Encoder. It's a board that modifies the POT, replacing the wiper with a magnet and sensor chip. It allows full rotation and 12bit absolute position. So you know exactly where you are all the time.

A quick overview found here. http://openservo.com/ConstructionTutori ... en-encoder

Oh my, that page is dated. I need to get around to updating it. The shaft is now an SLA rapid prototyped part, so it's much easier to assemble, and you don't need to hack an alignment tool. Search the forums for OE and you should find more about it among the posts here.

I believe one potential problem you have with the 3.5 turn POT is accuracy, the PWM signal can only be so accurate, and you loose your find control over the larger turn ration. OE is more precise than most servo's and it's full rotation.

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