RE: Led-switch Alternative

["Ward, David" <DAvid.Ward@xxxxxxxxxx>]

wierd,

I didn't have that bother when I used them :S
I used the QT110, QT115, and QT60326 on several projects, I've not used the
QT160 though

In one instance I had used 4 QT115s,  with white LED backlighting dimmed
via PWM using a Parallax BS2 (so not quick ;)
The sensors were comprised of solar window film about 10mm x 60mm and
spaced 5mm apart,  these were stuck on the back of a sheet of smoked
Perspex which made the top of the exhibit.
The LEDs were placed in a light tight box covered with a milky translucent
Perspex on top of which was placed inversely printed words on clear film
i.e. the light shone through the words on a black background.

The BS2 lit all the leds/words and when one word was touched the other
words would fade

I've just realised whilst trying to describe this - wish I had a camera
back then :( - that the final operation didn't rely on sensing the QT
devices whilst dimming,  though whilst building and testing I do remember
going through a phase of different LED brightness levels  (via PWM) with
the designer, and I don't remember seeing issues with false triggering - at
least not with the 115s

Dave


-----Original Message-----
From: ian.bird@xxxxxxx
[mailto:ian.bird@xxxxxxx]
Sent: 19 March 2005 18:55
To: ukha_d@xxxxxxx
Subject: Re: [ukha_d] Led-switch Alternative



Hi Frank

I am also experimenting with these for some touch buttons I am
building. I
am using the QT160 parts (6 buttons), which ones are you looking at?

If you are going to have your LED's in the same plate you are using for
touch sensing you will need to capacitively decouple every component of
the LED i.e. one cap before the LED, one after it and another after the
resistor. I also asked Quantum about dimming using PWM for
LED's in this
situation and they did not know as they had never tried it. The
potential
problem being the continual switching of the LED on and off might upset
the capacitance field sensing circuitry. I guess the
alternative would be
something like a digital pot but I don't know whether that
would work or
not.

>From what I can see it would not be too difficult to make a one
or up to
six button switch plate and give it the driving logic to switch low
voltage coils in relays. These relays could then control the
LD11 units as
Gareth would like to do.

Ian







"Frank Mc Alinden" <fmcalind@xxxxxxx>
19/03/2005 05:51
Please respond to ukha_d


To:     <ukha_d@xxxxxxx>
cc:     (bcc: Ian Bird/CV/Novartis)
Subject:        Re: [ukha_d] Led-switch Alternative



Hi Gareth

> And mebe we could figure out how to use these to control a 240v signal
> from an LD11 ?

I assume you mean the manual contacts on the LD11
..??......Currently if
i
need to operate dry contacts to switch 240xv  i would use
xPL-DMX  since
i
have the Dmx controller and relay board....and xPL has a Dmx
plugin.....im
sure the something similiar applies to xAP and others....
No Cbus .........????

Frank


----- Original Message -----
From: "Gareth Cook" <g@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Saturday, March 19, 2005 6:23 PM
Subject: Fw: [ukha_d] Led-switch Alternative


>
> And mebe we could figure out how to use these to control a 240v signal
> from an LD11 ?
>
> G.
>






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