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Old Apr 18, 2013, 11:19 AM
Flying high!
Finland, HKI
Joined Mar 2013
46 Posts
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V911 FFF Speed Mod or the servo resistor mod

Improving FFF by making a resistor mod to V911 servo

Coolthoughts posted here a post that I found very interesting. His newer V911 (a clone) was more sluggish than his older rev. 05 V911. He traced the problem to lower servo voltages in the newer bird. The post seemed to go unnoticed, so after a while I pm'd him and asked if he had found a solution. And indeed he had.

Coolthoughts' solution was to add a resistor to the lead of the pot of the servo. A servo has a feedback potentiometer that tells the servo motor if it should turn more. This mod changes the range of the potentiometer so that the motor turns the servo horn further.

I made the mod for my rev 05 V911. Coolthoughts used a 1k ohm resistor and I used a 470 ohm one. The weather has not been my friend lately, but I just managed to find a little time between rain showers. The wind was still way too strong for relaxed flying, but I had enough FFF speed to fight it. Even the smaller resistor made a clear difference on the angle of attack, and the copter can now fly alot faster and has more authority when flying in the wind. I'm very happy with it, but I wouldn't do this mod to my rev 07 V911 as it can easily reach steep enough angle of attack. With a steeper angle more of the motors thrust is translated into forward motion instead of just lifting it up. Edit: With a 470 ohm resistor the range went from 71 degrees to 84 degrees, so it's 118% of the original. Coolthoughts reported that with 1k ohm resistor the range is 140%.

How to do the mod?

First you need to take off the fuselage and locate the pot leads of the servo. (Note: we are looking at the circuit board from the front, so left and right accordingly.) Pot leads are those three legs right next to each other just below the date. Leave the center pin alone. One of the outer legs is not connected to anything, leave that alone too. (The lighter green area on the circuit board are the connection lines.) The third pin (in my rev 05 and rev 07 it's the left one, I'm not sure about the others or the clones) you need to cut the line leading to the servo behind the board. Then pry it up. See the pictures.

After prying the pin up you solder a resistor between the pin and the place attached to on the front of the board. You can use a regular resistor or do it the hard way, like I did, and use a short piece of wire and a surface mount resistor.

My other mods and tutorials: http://www.rcgroups.com/forums/showthread.php?t=1846171
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Last edited by luovahulluus; Apr 18, 2013 at 12:49 PM.
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Old Apr 18, 2013, 11:45 AM
What is a controlled landing?
bebeep89's Avatar
United States, WI, Sun Prairie
Joined Feb 2013
754 Posts
Nice!!!
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