Whoooosh..thud..oh bugger

[Martin Howell <martin.howell@xxxxxxxxxxxx>]

This is not really HA, but it's close.  My massive
electrified sliding door project is almost completed, but
now that the glass is in and the weight of the door is up to
maybe 70Kg, the intertia of the door kinda mashes the drive
cable mechanism when the drive motor stops and the door
tries to keep on going.  This was the main logic behind
electric drive, as I wanted to avoid small boys being
squashed when the door was closed too enthusiastically
(though quite why, I'm not sure, it seems the sort of thing
that small boys deserve :-))

I could install stronger cables etc but that would not
really solve the problem, and a mechanical braking system
will still put too much strain on the drive train.  Instead
I'm looking for some electronic means of starting the drive
off slowly, then speed up, then slow down as the door
reaches the end of its travel. It would be easy to fit
microswitches to change from speed A to speed B, but the
drive electronics are beyond my limited skills - I can build
a circuit, but can't design one.  The drive motor is 12v (as
is all the electric gubbins), and the current obviously
reverses each time the motor changes direction. The
mechanism is presently operated by a pair of standard car
electric window switches, so they drive the motor when
pressed and it stops when the switch is released.

Anyone have any ideas?  Thanks

Martin
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