Hi there David
I think the problem is a very important one indeed. In the past most of
these switches - with 3.5mm jacks - have been used with non- critical
devices. Also cost has played a part I am sure so the cheapest components
are used (3.5mm jack) which also allow for home servicing. When it comes to
driving with powered chair things are different. Personally I do not
believe a 3.5mm jack plug is safe enough to be used to drive a chair. Also
in the past some switch controllers for powered mobility would only come
with their own set of switches as providing a socket meant the manufacturer
had no idea of the sort of rubbish that could be plugged in. Come to think
of it I remember a well known ECU manufacturer who also provided their own
switches with their own type of plug so that they knew the whole system.
I would very much welcome a standard for switches with perhaps grades for
use. I would also like to include the connector type in this. If I ruled
the world I would do away with 3.5mm jack (except perhaps for 'very light
use with toys etc') and have switches terminating in something like a Lemo
micro coaxial connector via coax cable (would help emc issues as well) -
now that would be quality. Ok so it would cost loads (£100 a switch instead
of £30) - but these switches are absolutely critical to users and are being
connected to £000's worth of kit.
So in Novitatech going to set up a standard? - please do.
Colin Clayton
At 05:16 18/02/2005, David Hobbs wrote:
>Hi everyone,
>
>my apologies if you receive this email more than once, but I wanted to
>send this message to a few networks and get as much feedback as possible.
>The issue of switch reliability and switch lifetime has recently become a
>hot topic, and a client I was working with yesterday was a prime example
>of this - he accessed a switch using his foot (it was recessed into his
>footplate, with a plastic cover over it) and it would remain "on" when
>pressed (that is, stuck in the on state). Not an ideal situation for any
>switch activity, let alone one that uses a switch for integrated
>wheelchair control.
>
>I wanted to ask you the following questions:
>
>- have you (in any capacity, i.e.: as a switch user, therapist,
>technician, engineer, funder, etc) had similar switch experiences? I
>wanted to get an appreciation for how big this issue may be. Are switches
>regularly failing or is it just isolated incidents?
>
>- do you know of a standard for switch reliability or switch lifetime? How
>many presses is a switch meant to last for? Obviously this depends on
>frequency and use, but perhaps a minimum lifetime can be determined or
>specified.
>
>- do manufacturers state how many switch presses their products can
>sustain, and do they give any recommendation on lifetime? Does anyone
>proactively conduct a client 'switch check' - i.e.: evaluates and checks
>the switch for integrity and function, like preventative maintenance, over
>a given time frame (annually, bi-annually, etc.) when a client comes in
>for a clinic session.
>
>Thanks for your time - your responses are greatly appreciated. Even if you
>don't know the answers to any of the "standard" questions I've asked, but
>you do have personal experience (or anecdotal) of switch failure, it would
>be great to hear from you.
>
>Cheers, and have a great weekend.
>
>Dave ;-)
>
>David Hobbs
>Senior Rehabilitation Engineer, Churchill Fellow
>NovitaTech
>(formerly 'Regency Park Rehabilitation Engineering')
>PO Box 2438, Regency Park, SA, Australia, 5942
>Ph: + 61 - 8 - 8243 8338
>Fax: + 61 - 8 - 8243 8208
>Mob: 0418 221 811
>Web: <http://www.novitatech.org.au/>http://www.novitatech.org.au/
>Email: <mailto:[log in to unmask]>[log in to unmask]
>
>"Somewhere, something incredible is waiting to be known."
> - Dr Carl Sagan
>
>
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Colin Clayton BSc, CEng, MIEE, MIPEM
Great Ormond Street Hospital for Children
The Wolfson Centre
Mecklenburgh Square
London WC1N 2AP
Tel: 020 7837 7618
Fax: 020 7833 9469
visit www.wisedx.com
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