Dimmer circuit so your aftermarket gauges dim with your dash

Looks like After market gauges are not dimming with the dash due to the way subaru illumination works.

 

Subaru doesn't use a fixed ground for illumination There is a fixed +12V (ILL+) which is either 0 (lights off) or +12 (lights on) and a floating ground (ILL-) which varies from 12 (fully dim) to 0 (fully bright).

 

It looks like most people just connect to the ILL+ line. However they loose the ability to dim the after market gauges. Because ILL+ is either +12 or 0 depending if the parking lights are on, the after market gauge illumination is just on/off.

 

Is this a problem for many? Any interest in a circuit that converts Subaru illumination to a compatible format used with after market gauges.

 

Here is some posts I found that discusses the problem:

 

http://www.legacygt.com/forums/showthread.php?t=103176

http://www.scoobymods.com/archive/dim_omori_elect_gauges-t3115.html

interested...

If you like to, I can make you something custom for this. I have my own electronics r&d business and I can accept little projects like that. I can give you only the concept and you buy the pieces to build to thing, or I can give you completely built and tested kits.

 

Some people here know me because they bough me the Leptronix aux in kit for the Subaru Legacy. Everyone seems to be very satisfied with the product and with the service.

 

Please inform me of your interest.

I'm just trying to understand if the community is generally interested in a solution to the illumination problem. I have a few ideas rolling around.

 

BTW - Great job on the Leptronix aux in kit. A unique solution.

I'm just trying to understand if the community is generally interested in a solution to the illumination problem. I have a few ideas rolling around.

 

yes

Just setup a relay that actuates on +12v from the car dimmer circuit and connects ground to the dimmer circuit in the guages.

I am talking about a variable dimmer, not just an on / off solution. So in this case a relay would not work.

don't know if this helps; but the sti gauge pack dims with the dimmer knob.

I am talking about a variable dimmer, not just an on / off solution. So in this case a relay would not work.

 

 

i see. would the guages accept that type of variable voltage?

in for results....I have 4 gauges to potentially dim...

Idea for a product: http://legacygt.com/forums/showthread.php?t=73568

i see. would the guages accept that type of variable voltage?

 

To do it right...I think the dimmer conversion circuit would have a PWM output. This should work for all gauge types, LED or incandescent.

 

I think it would need a calibration button to match gauge brightness with the dash brightness.

I wonder if you could integrate it with Defi BF gauges. They dim, but they are independently controlled by the controller. I am afraid the communication between the controller and the gauges is digital, so it would require quite a different approach of hacking into the controller and integrating it to the car controls. Being product specific, no go, I guess...

Can you elaborate on why Subaru's method of a variable ground doesn't work with aftermarket gauges? Is it because it includes positive voltage rather than a simple resistance change?

I wonder what's in the sti gauge pack that works with the dimmer then. maybe it's just a simple logic circuit.

Can you elaborate on why Subaru's method of a variable ground doesn't work with aftermarket gauges? Is it because it includes positive voltage rather than a simple resistance change?

 

Actually it's because Subaru illumination runs essentially a negative voltage. When the parking lights are on. The parking light Net (Purple in our cars) goes to 12V reference to our cars system ground. The variable illumination in our legacy's is actually the potential between that net and the variable illumination net (color = BW)

 

So when we are at full brightness BW is Low close to Ground. When our stock gauges are dim the BW line is higher closer to 12V which yields a smaller potential voltage difference and thus dim lights.

 

The problem trying to tie in after market gauges to our cars is the fact that most of these gauges illuminate without an isolated illumination gnd. Meaning that we can only tie them the parking light net (purple) and have on/off illumination. If we tie them to the variable illumination line (BW) this line does not reference ground and thus won't work.

Looks like After market gauges are not dimming with the dash due to the way subaru illumination works.

 

Subaru doesn't use a fixed ground for illumination There is a fixed +12V (ILL+) which is either 0 (lights off) or +12 (lights on) and a floating ground (ILL-) which varies from 12 (fully dim) to 0 (fully bright).

 

It looks like most people just connect to the ILL+ line. However they loose the ability to dim the after market gauges. Because ILL+ is either +12 or 0 depending if the parking lights are on, the after market gauge illumination is just on/off.

 

Is this a problem for many? Any interest in a circuit that converts Subaru illumination to a compatible format used with after market gauges.

 

Here is some posts I found that discusses the problem:

 

http://www.legacygt.com/forums/showthread.php?t=103176

http://www.scoobymods.com/archive/dim_omori_elect_gauges-t3115.html

 

 

Has anyone here tried this out yet? I'm tempted to try it out since my STRI gauge is bright at night and its finally starting to get annoying now.