Digital Dash (Green) Conversion (urq)quattro/coupe

[Huw Powell]

> When pushing the dimmer-knob for 1 sec, only the speedo is visible right?

so right you are, what a cool feature.  I don't own a digidash yet, but
I do have an '87 cgt manual and dimmer switch to look at so i can see
what you are talking about.

>
> Picture this: I would like to trigger this 'dash-mode' with an external
> device. This particular device (Stinger, aka Bel radar detector) has visual
> led's and an adjustable audible warning system.
>
> It would be VERY nice if I could use the push button to switch my
> radar-detection device on/off, and better yet, the warning signal from the
> radar would trigger the dash mode on/off, so when I'm entering a radar
> control unit, the dash 'blinks'. Wouldn't that be cool.

yes, sounds great.

> I'm still figuring out how to convert the 0 / +2 volt led 'trigger' into the
> dash-mode on/off and the original 'push' to switch the radar device on/off,
> but first I'll have to know how the push-button operates.
>
> How does it work? ie. a switch or a resistance (like the dimmer).

OK, the switch in the dimmer is simple - it's a normally open momentary
single pole switch, the two terminals on the inner end (towards the
cluster) are closed, only when you are actually pressing the knob in.

So you have two engineering tasks to perform.

One is to make it so a momentary switch like this one can turn on your
radar detector - whihc may have to be cut into to do this.  if it has a
"two position" on of switch it will be harder, you'd probably have to
use a latching relay (stays on or off after the last switching pulse) to
power the detector.  Still, not rocket science.

Then you want to take your detector output ans use it to perform this
cluster dimming task for you.  You have a 2 volt trigger to work with,
and it runs an LED so it has at least some small current capability.
What I did with the built in detector in my car, with similar "driving"
capabilities, was trigger a "reed relay" (readily available at radio
Shack) with it.  The reed relay works on something like 50 mA, so it
won;t overload your detector's output, and the one I got was sensitive
to fairly low voltage as well.  Then the reed relays output is used in
place of the dimmer switch - ie, it is hooked up to the cluster in its
place.

Doing all this should work, should make the cluster flip between modes
when the detector goes off.   You might want to add a buzzer of some
sort (I mounted a very loud one from RS under the cluster cover), with a
disable switch of course, and fire it with the reed relay (or another
relay piggybacked on the reed's output) to get a nice loud audible alarm
for daylight trap entry - the flashing cluster might not get your
attention fast enough (like the blue lights I added to my cluster -
gotta have the buzzer as well in daylight).

Good luck working on this great idea, and let us know how it turns out!

--
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/