Servo behavior question / advanced servo/PIC programming question

[ChrisH]

Originally Posted by SuperDanman

Alright, so up to this point, it seems that
1) I can't make a signal to trick a standard 120-degree servo to go over its range
2) Most hobby servos are designed to do 120-degrees, and this fact is implicit in their datasheets (ie not stated directly).


Does anyone know a source where I CAN get servos that go 180 degrees or more? Or at least a particular model that goes 180 or more? The HSR-5995TG does, but thats a fancy digital servo that costs $20 more for features I don't need at all (and since I need a bunch of these servos, the cost is really too much).

Otherwise, has anyone made any definate tests that if you go outside the RC PWM spec (ie pulse < .9ms or > 2.1ms) the servo doesn't like it? Some hobby RC sites I've seen kinda suggest that you CAN do this (most of the people talked about changing or adjusting the pots on their recievers). I spent about 8 hours today trying to make something to make that test waveform, but so far I'm having no luck.

The easiest way to get 180 degrees is to mount a big gear on the servo output and mesh it with a gear half its diameter. Depending on what you are trying to do, you could also use a linkage to get the same effect. The linkage could have spots where it binds near the end of its travel so I'd tend to go with the gears. In any case, you wll get a decrease in available torque. So you might have to use larger servos. Everything has its price.

Doing this electronically has a certain elegance, but sometimes a mechanical approach is better.

ChrisH