Servo Reversers.... how do they work?
 

I might be needing a Y cord that has a reverser in one side. My 6XA transmitter doesn't support dual elevator servos. How does that reverser work? It can't be as simple as crossing two wires can it? Are there any downsides to a reverser?

Thanks,

Ernie

RE: Servo Reversers.... how do they work?
 

Given a sound design, there are no downsides to a servo reverser other than it is another component that may fail.
I have used them now and then and never had a problem.

In principle the design is very simple. A servo gets its position information from the length of a pulse that is repeated many times every second. The pulse length varies between 1.0 and 2.0 ms with 1.5 ms representing the neutral. In order to reverse the servo we need a circuit that converts a 1 ms signal into a 2 ms signal and vice versa.
In order to accomplish this a typical servo reverser produces a 3 ms pulse and subtracts the incoming pulse from that value.
A 1 ms input pulse produces a 3-1=2 ms output pulse and a 2 ms input pulse produces a 3-2=1 ms pulse, exactly what is needed to reverse the direction of the servo.

For the technically inclined: The easiest way to accomplish the subtraction is to do a logical XOR between the input signal and a 3 ms reference pulse that is triggerd by the rising edge of the input signal.

RE: Servo Reversers.... how do they work?
 

If your comfortable with opening the servo and soldering, a servo can be reveresed.

The Two motor leads are reversed, along with the "Outside" leads on the feedback potentiometer ( Variable resistor).

Not hard to do ... "IF" you are comfortable.

Some of the new servo can be reversed by using a programmer ... a little expensive if you are only doing one.

FMA Direst has a "Hand Adjustable" Servo that can be adjusted for reverse, center and end points just by moving the servo "by Hand".
It is digital and about $30.00 ... P/N DS 300BB ... check it out ... if it will work for you, You will have another servo for the price of a reverser.


Good Luck !

RE: Servo Reversers.... how do they work?
 

You can also use a Futaba servo and a Hitec servo since they turn in opposite direction! I use this method on all my planes that have two elevator sevos. Seems to work fine


Lonnie

RE: Servo Reversers.... how do they work?
 

Lonnie, very interesting about using the hitec and futaba....... did you find two servos with the same specs?

Thanks,

Ernie

RE: Servo Reversers.... how do they work?
 

Close enough that I cant tell the differance! I fly mostly Fun scale planes. no 3D stuff. Now if you are flying pattern or IMAC maybe those flyers can tell the differance

Lonnie

RE: Servo Reversers.... how do they work?
 

You can order most all of JR servos "reversed" or "normal" rotation, if you do not want to use a reverser.

RE: Servo Reversers.... how do they work?
 

The best one out there. No adjustments, match up both sides mechanically and it's good for life. Very consistent.

http://www.electrodynam.com/cgi-loca...1b3+1141431302