Papabravo said:
So, will servos that sees pulses at the right frequency, 50 Hz., but less than the minimum specified width go to the stop in the CW direction or will they just stay where thry are, not knowing what to do so to speak? For that matter what happens for pulses that exceed the maximum?
The 50Hz frequency is VERY non-critical, only the pulse width really matters, I presume there is a point where the frequency can cause problems?, but anything from 25Hz to 100Hz (and probably more?) is fine.
As for the pulse width itself, notice that the servo only gives 45 degrees movement for the 1mS pulse change - it uses a 270 degree poteniometer to control it's position, so 'theoretically' it could move 270 degrees. However, I suspect that's not very likely
You need to consider their design criteria, it's important to remember that they are designed for multi-channel remote control of models - with aircraft being a common use.
So, as far as the frequency goes, you need to make it high enough for the servo to get the command 'instantly' - as far as the operator is concerned. If it has to wait too long then the plane might crash
, but even a small noticeable delay would make it un-flyable (see another thread about this!). That's the 'too slow' side dealt with, the other side of the storey is 'too fast', this is restricted by the number of channels in use - if you have eight channels then the pulses alone require 16mS (8 x 2mS), which you can just squeeze in your 20mS time frame.
Likewise with the pulse widths, if you increase your 8 channels to 3mS then the pulses alone now take 24mS, which won't squeeze in the 20mS window.
As far as the movement is concerned, 45 degrees is all you need, and you design the model based on that - but for a robot, when NONE of the above design criteria are required, you can safely push it beyond it's normal design limits. I've no idea how far you can actually go?, and it probably varies from make to make, but I seem to recall 90 degrees is easily attainable?.
Perhaps someone might like to test one and see?, I keep meaning to - I bought a two channel radio control set a couple of years ago, with a view to a new PIC tutorial - but I haven't got around to it yet