Continuous Rotation

[mechpb]

Obtaining 360 deg of movement and maintaining proportional position would be nice for a camera pan axis, but the only way seems to be either hacking a servo for continuous rotation, (which would eliminate the proportional positioning), or using overdriven driven gears, which will reduce torque by approx 1/2.
Before I order any gears for my homemade pan servo, (probably stick with 180 deg or 1:1 ratio), I was hoping someone had a miracle solution for my proportional 360 deg dilemma. :)

[pmpjohn]

A sail winch servo ( the type used to turn a drum not the type used to turn a long servo arm ) will give you a continuous 360 deg of rotation in both directions but is not proportional. The only way to tell what you are pointed at would be with a real time downlink.

John

[Greg McFadden]

You could get 360 degrees via the following hack.... You buy a new and appropriately designed POT. (or just use your old one, but a new one would probably be better)

You measure how much angular deflection you get on your current servo with 100% ATV (or End Point Adjustment for non-futaba people)

Now, here is what you do... you put one of the servocity.com gears on the output spline... it runs to a larger gear, who's size is determined by knowing how far, angularly, you want the main output to move, and picking the appropriate sized large gear to mate with the small output gear. This large gear is coupled to your POT which has its leads soldered to the servo circuit board in place of the stock POT

then you simply find a way (via gearing or a custom servo spline extension) to output to the servo travel to what you are trying to turn.


OR.... do the same thing but put the POT and appropriate gearing on what is actually turning (camara mount for example) then wire back to the servo... and make sure that for both of these the servo has a continuous rotation gearset in it...


but there you go, a Proportional, as many degrees as you want, servo

[William A]

Maybe here.....
http://www.fortunecity.com/marina/nelson/479/Bas_360_R.html

I did the 'method 2' for a home security camera system here awhile back that worked OK.

[Mr.RC-CAM]

The PanCam project offers an alternate method of controlling the servo. It converts proportional position to proportional speed and has other features for Pan & Tilt applications. If would work with a servo modified for proportional 360 degree use.

Just see the RC-CAM Special Projects Page: Click Me. (http://www.rc-cam.com/projects.htm)

Regards,
Mr. RC-CAM
www.rc-cam.com

[mechpb]

I checked out the link at
http://www.fortunecity.com/marina/nelson/479/Bas_360_2_R.htm(method 2) and i guess i have a couple more questions about POTS.
In my application I want the larger gear to be the driven axle for the pan axis thereby reducing the load on the servo.
I suppose it's simple to connect a POT to 1/4" steel axle?
Any suggestions for my Hitec HS 200's and 645mg's? Do they operate similairly to the Futaba servos? :)

[Mr.RC-CAM]

I suppose it's simple to connect a POT to 1/4" steel axle?If you can machine parts, it is a breeze. You can purchase pots with long 1/4" shafts too, so they may help your effort. But, if you want full 360 degrees, then the pot will need to be geared a bit more since they do not usually allow 360 rotation.

Any suggestions for my Hitec HS 200's and 645mg's? Do they operate similairly to the Futaba servos? All modern servos are basically the same. The only gotcha is that some have convenient wire leads to the pot, whereas others connect the pot directly to the circuit board. The latter is a bit more work to hack.

Your best bet is to just buy the parts and then experiment. It will all make sense when you have the parts in front of you.

Regards,
Mr. RC-CAM

[William A]

And if your planning to use gears and/or sprockets and chain as your final drives.
Checkout Servo-City

http://www.servocity.com/ServoCity/Products/Servo_Power_Gearboxes/servo_power_gearboxes.html

http://www.servocity.com/ServoCity/Products/Sprockets__Gears__Chain/sprockets__gears__chain.html

[mechpb]

Your best bet is to just buy the parts and then experiment. It will all make sense when you have the parts in front of you. I did notice SC had a couple new items including a gearbox with external POT. Maybe that's the way to go. Their website doesn't state the deg of rotation their 4:1 setup will provide. It appears their POT is already connected to a 1/4" shaft so maybe they will sell me just the POT and gears for experimentation purposes.

Does the increased rotational speed of the servo motor have any negative effects on the servo itself? I take it they weren't designed to run that fast but alot of people use this method i guess so it must be 'cool' to do it that way.

I'll eventually look into the PanCam method for controlling this rig. Unfortunately, I have to use a servo to trigger the shutter on this Stylus 80 (it was cheap). I did manage to dissect the camera from the case and expose the shutter button, but I was unsuccessful at hacking into the circuitry. I did manage to re-assemble the camera though, and it still works. :)

[mechpb]

k one more thing i forgot to ask
Where can you find specs on which servo turn what # of deg., or am i missing something here.
Thanks for the info BTW. :)