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/
Email: [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
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