Re: Re: Whoooosh..thud..oh bugger

[Martin Howell <martin.howell@xxxxxxxxxxxx>]

Funny you should ask...  Some pics and details are rather
hastily chucked together at

wwww.grizelli.com/partition/partition.htm

When the door is working properly, I'll add some moving
pictures as well, ooh er missus.  The drive is disconnected
at present as SWMBO can't seem to master the knack of taking
her finger off the switch before (rather than 3 seconds
after) the door hits the buffers at 40 mph, and I'm worried
that the whole thing might end up in the garden.

Martin

Paul Gale wrote:
> Any pictures yet?
>
> Would be interesting to see...
>
> Paul.
>
>
>> -----Original Message-----
>> From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx] On Behalf
>> Of Martin Howell
>> Sent: 11 April 2007 17:56
>> To: ukha_d@xxxxxxx
>> Subject: Re: [ukha_d] Re: Whoooosh..thud..oh bugger
>>
>> Thanks Simon, not as strange a suggestion as it might seem.
>>   I originally planned a fully automated system, using a
>> controller devised by Rodney Hall (on this list, thanks
>> Rodney), but decided against it on the grounds that it would
>> be pretty complex - IR beams to trigger both open and close;
>> obstruction detection; manual overrides etc - and that it
>> would need too many fail-safes to stop it from squashing
>> people, and avoid getting Aunt Edna getting trapped in the
>> lounge for several days while we worked out what had gone wrong.
>>
>> I'm sticking with the simple manual approach for now, with a
>> series of micro switches to slow the door down for the last
>> 6 inches of travel and to shut the power off before the door
>> hits the stops, together with some cushioning of the cable
>> drive mechanism.  As a last resort (and with higher WAF), I
>> could disconnect the drive completely and just add a handle
>> on both sides, though there's still the problem of small
>> boys closing the door enthusiastically and forgetting to
>> move all their body parts out of the way...
>>
>> Martin
>>
>> Simon Pawson wrote:
>>> I tried this reply last night but haven't seen it yet...
>>>
>>> Coming totally from a strange direction....
>>>
>>> could you do something with a reversing sensor system for a
car. The
>> bar
>>> graph of LEDS could be converted to opto-isolators driving
relays
>> with
>>> build in resistors to slow the travel.
>>>
>>> Might be hard getting a reliable bounce if wall/frame mounted.
Easier
>>> spotting the wall from the door but not so elegant. Could be
set up
>> as a
>>> safety measure as well. Child in the way stops (or even
beeps).
>>>
>>> Sorry just an odd thought - back to the merlot.
>>>
>>> Simon
>>>
>>>
>>> In message <461A91D0.8000200@xxxxxxx>, Martin Howell
>>> <martin.howell@xxxxxxx> writes
>>>> Hmm, this unit from RS gives the 'soft start' I'm looking
>>>> for, but not the 'soft stop, which is where the real
problem
>>>>  lies.  I agree with your analysis of the drive train
>>>> issues, but I'm concerned that strengthening the cables
and
>>>> applying more tension will just move the force to the next
>>>> weakest part of the drive - the cable fails at present
>>>> because of a joint, inserted partly to prevent breaking a
>>>> more difficult to fix part of the drive.  I'm looking at a
>>>> more simplistic system of forcing a slow down at each end
of
>>>> the movement, watch this space to see if it works, or if
the
>>>> whole contraption bursts through the wall into the garden
:-)
>>>>
>>>> Martin
>>>>
>>>> David Cole wrote:
>>>>> 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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>> --
>>>>
>>>>
>>>> Grizelli Associates Limited
>>>> IT Project Consultants
>>>> 2c Nethermoor Road, Middlezoy, Bridgwater, TA7 0PG
>>>> UK Company registration no. 2468872
>>>> VAT registration no. 713 1775 49
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>> --
>>
>>
>> Grizelli Associates Limited
>> IT Project Consultants
>> 2c Nethermoor Road, Middlezoy, Bridgwater, TA7 0PG
>> UK Company registration no. 2468872
>> VAT registration no. 713 1775 49
>>
>>
>>
>>
>>
>>
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--


Grizelli Associates Limited
IT Project Consultants
2c Nethermoor Road, Middlezoy, Bridgwater, TA7 0PG
UK Company registration no. 2468872
VAT registration no. 713 1775 49