Re: Whoooosh..thud..oh bugger

["David Cole" <davecole_uk@xxxxxxxxxxxxxx>]

Martin

Sounds to me like you need a PWM (Pulse Width Modulation) drive to
efficiently control the speed of the motor.

Something along the lines of 510-1209 at RS should do it, this would
give the acceleration and deceleration whilst also limiting the
current if the door jammed. Alternatively google for PWM DC drive
circuit

You want to ensure that your drive train (cables) are as stiff as
possible, this is why industrial applications usually use rack and
pinion drives. This may mean increasing the diameter of the cable to
ensure that you don't have any stretch which causes jerk. It sounds
like you have a lot of inertia in your system it may help if you add
additional gearing which will reduce the speed, increase the torque
but also decrease the amount of reflected inertia seen by the motor.

Hope this helps

Regards

Dave