Duty cycle in 555 astable timer

If a servo needs a 1ms pulse and the Hz is 50, the T(mark) is 1ms and T(space) is 19ms. The formulas break down if T(mark) is less than T(space). How do I make this work? I've hooked a servo to every circuit I've found on the net and although I can kind of get it to work, it jitters all the time instead of moving to a position and stopping. If I adjust the potentiometer (between R1 and R2) the servo changes position, but will still jitter and move in either direction. This is not how it should behave. Please help.

Posted by bkr1969 (brian@brianredmond.net) on 07/11/2009, at 17:22 GMT