F2G-1

My Feedback: (13)

How does the matchbox actually work?
Does it just change each servos endpoints and centers to match desired motion, in an attempt to match actual motion at the controll surface, because of servo potentiometer tolerence?
Does it detect load for each servo and adjust?
I'm working on a custom Flap (linear actuation) servo for my 27% Cessna 310R and worried that a 20% to 30% potentiometer tolerence of a slide pot (90 mm long, in the feedback system) might cause asymetrical motion (when ganged for each of 4 flaps) And hope that a matchbox(s) would aleviate this condition.

Thanks,
Ted

Mr67Stang

Be right back. I need to go get my doctorates degree and come back and read that again

Simply put a Matchbox allows you to sincronize the movement of up to four servos/controls. Sometimes used for multi-engine throttles, flaps and large planes with multiple servos on a single control surface. Yes, you can look at it(adjust it) from both sides. Be it equal movement of the servos or adjust for equal movement of the control serface. Since it is nearly imposible to get the geometry perfectly identical on both ailerons for example the same movement of each servo will not give the same movement to each aileron. With a matchbox you can adjust the servo travel individually and achive uniform movement.

fizzwater2

My Feedback: (61)

If you set the pots up as a voltage divider, rather than depending on actual resistance, your matching tolerances should end up closer than that. All you need to worry about in that case is linearity of the pots, not actual resistor tolerance.

Surely there's someone out there making linear pots with decent linearity. We used to be able to get wirewound pots (excellent linearity, but somewhat "steppy" in response due to the individual turns of wire) with a conductive plastic layer to smooth out the steps - Clarostat or Bourns, I think was who made them, called them hybrids or something like that.

F2G-1

My Feedback: (13)

fizzwater, thanks.
Rather than re-invent the wheel, I think Im going to caniballize a standard servo, replacing the rotary pot with the slider.
Is the amp/controller comparing resistance or voltage on these hobby servos?

I've found a plethora of linear taper 5k slide pots out there, but in the 100 mm range is few and far between. I found one that might fit the bill, but no spec on the construction.
If its wire wound no problem, 'grainy' flap deployment wont bother me too much. I'm more worried about resolution issues as we just spread it over 100 mm rather than 60 degrees.(hence my matchbox questions)

If all else fails, I could go with micro limit switches, but a 3 position circuit might prove challenging for me - any ideas?