Thread: motorized potentiometer

Originally Posted by scott_fx

im sorry, my above post was a bit misleading. i was saying that i need the pot, gearbox and motor... from the servo.

i see, it is now as clear as mud.. to many ideas

Originally Posted by scott_fx

I want the knob for local adjustments and an alternative to using the computer. My current version of this setup is tablet based (win7). I have the tablet connected to network usb hub via a wifi router. This leave the tablet completely unteathered and can be anywhere on the boat. for instance: say my g/f wants to choose some music while she's at the bow of the boat. If i wanted to adjust the foil, it would be great to just turn a dial without having to grab the tablet. On the other hand, i am also going to have a 'preset' skin that will fill the ballasts, and set the foil position (possibly even set the cruise control speed). With that in mind; if i hit the preset from the tablet, the knob would be out of sync.

pretty much how i was thinking you wanted it..

Originally Posted by scott_fx

my options would to either have a continuous rotating rotary encoder and then some sort of digital display.

this was my next thought-- not the digital display, just to use a rotary encoder to connect to the pc, and update the pc screen.

Originally Posted by scott_fx

-or-
a knob that would self adjust based on the foil's position

..which is why you were considering the servo idea. i'm starting to catch on..

Originally Posted by scott_fx

i think the latter is cooler.

agreed. you could also use a argument that it is easier to see where a knob is set then to look at a pc screen, or that the tactile feel of a knob makes adjustments require less visual attention

Originally Posted by scott_fx

I'm thinking that I could bypass the 'brains' in the servo and wire up the fb to the servo's internal dc motor and pot. I would then attach a knob to the servo shaft. when i turn the knob; it would turn the pot, giving the fb an analog input. If i set the foil's position digital from the tablet, the fb would spins the motor and obviously it would in turn also spin the knob and pot.

do you think that would work?

ok, so i see where your going..

i have my doubts.

here's the problem i see--i own 3 'premium' rc vehicles(have a total of 5-- 2 of 5 have built-in linear servos that you could never move in this manner):

servos connected to a standard knob are going to be very hard to turn-- the gear reduction in them means that you need a decent amount of force.. you would need a knob similar to this:
http://search.digikey.com/scripts/Dk...me=450-1728-ND

smaller servo's are easier to move, but those can also be a larger problem because the individual teeth are smaller, and they are not designed for constant exterior force--so they are easier to break--at least with plastic versions, like my eflight ds75's..

the second problem is that servo's are not exactly precise when moving by external force-- once you start to get a servo moving, without a large lever on it, it requires a lot of precision to move it to a certain spot within it's travel. so you might be able to move it from '1' no problem, but to predictably stop at '4' requires a lot of concentration..

in a perfect world, you could just add a electronic clutch that would disengage the motor and partial gear-train from the knob/pot to get a free-er moving setup(so the clutch would engage whenever the motor was powered, and disengage as soon as the motor de-energises), though, i have never heard of that before.. and the other problem with adding it is that there is no way you could use the stock servo case..

if your interested, i would need to dig them up, but i have 3 metal geared JR servo's i could donate to the project(i've got no use for them..):
http://www.amazon.com/241-Micro-Serv.../dp/B000BMBUVK

they were too slow for my heli, and they are analog, so they didn't work right(the other servo on that bird is digital, so it led to a twitch issue)...