I just found a really neat item called a "servo stretcher" http://www.servocity.com/html/180o_servo_stretcher.html does anybody know how these work?
I'm not sure how they work... but they do. I have 3. I think it has something to do with regular servos don't turn their full operational distance, I've seen other "DIY" versions that seem to be "tricking" the servo's electronics into thinking the motor is only 3/4 turned when it is infact fully turned.
What the site says: "Now you can have 180° rotation from just about any analog servo. The Servo Stretcher modifies the signal to the servo enabling it to rotate 90° either direction off of the center (neutral) position. It simply plugs in between your controlling source and the servo just like a servo extension. The total amount of rotation is dependent on the type of radio control or servo controller. Results may be slightly less than 180° or slightly more. If it is slightly less, using full trims will allow more rotation. Note: This product is not to be used with servos that offer more than 90° rotation from the factory or any brand of digital servos. Digital servo can be programmed internally for 180° rotation." Having messed around with servos & microcontrolers plenty, I can tell you that MOST (not all) typical hobby servos are physically & signal-wise capable of rotating about 180 degrees. MOST radios just don't send them a range of pulse widths that is as wide as the servos' capability. This makes sense: The radio makers don't want to overshoot with their signal, so they trim the range back. Something other than a radio can shorten or lengthen its generated servo pulses to whatever it wants to, even beyond the limits of the servo, where the servo will stall & consume way too much current, so it's pointless to go further (long or short pulse). Ahile back, I posted the results of an experiment with a Hitec sailwinch servo, where I determined its actual end points & total rotation (>4.5 turns, as I recall - it's spec-ed at 3.5, etc.). This is exactly what the "servo-stretcher" does. It "scales" the input pulse width to a wider or narrower pulse on the output side. It may be a calculated factor, or it may be a lookup table. Whichever method, you put a pulse width in & you get a (maybe) different pulse width out. I say "maybe" because, the closer the pulse width is to 1.5 msec. - the "center" of rotation, the closer the output pulse will be to the input, & dead center should be the same out as in. JM
